Content:

MAL – Medal and Award Lectures

MAL0 – EGU 2021 Angela Croome Award & Katja and Maurice Krafft Award Lectures

EGU21-15433 | Presentations | MAL0 | Angela Croome Award Lecture 2021

Communicating geosciences in the digital age

Roland Pease

It was in mid-March 1987 that I first took up my desk at Nature's bookish offices in Little Essex St, not quite 20 years after Jason Morgan's epochal and poorly understood AGU talk on the mechanisms of plate tectonics. Within days I was editing articles on the topic, which seemed as ancient and established as the mountains themselves. So, a further 30 years on, it's unnerving to recognise how young, yet successful the paradigm was. Climate science was similarly finding its feet at the time. These global forces that shape the planet, shape people's lives too, and often in an instant. This is what makes accurate and timely reporting of earth sciences compelling. What's also been transformed is communication. Then, it was by post, or via the new "fax" machine that arrived shortly after me. How that has changed! In this talk I will reflect on the the key role digital media, social media in particular, play in contemporary reporting on geosciences and the environment.

How to cite: Pease, R.: Communicating geosciences in the digital age, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15433, https://doi.org/10.5194/egusphere-egu21-15433, 2021.

As geoscientists we are used to being inspired by and seeing the physical and scientific value of the landscapes surrounding us. We are also used to questioning why and how landscapes evolve and as well as trying to unravel the complex interactions between the human and physical landscapes.  However, typically scientific results remain within the scientific community and there is relatively little engagement beyond that community particularly with underrepresented or hard-to-reach audiences.    

From making slime glaciers to discussing whether or not the flow of water over a crayfish in a river is the same as the flow of air over a Formula One car, running geoscience themed outreach and engagement events have provided me with some of the most exciting and rewarding times of my academic career.  In this lecture I will share some of the passion I have for ensuring academic research is shared, is accessible and is inspiring for everyone, not just scientists.  Using examples of how I have engaged with a diverse range of non-academic audiences from school children to governmental policy makers I will talk through the challenges and opportunities these engagement experiences have presented.

Looking to the future I will discuss the potential opportunities the geoscience community has for overcoming current barriers to engagement, the significance of training undergraduate and postgraduate students in delivering engagement activities and the importance of engaging citizens with scientists in order to understand and help mitigate against the impact humans are having on our fragile planet.

How to cite: Ockelford, A.: Is the flow of water over a crayfish in a river the same as the flow of air over a Formula One car; opportunities and challenges of outreach and engagement in the geosciences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11034, https://doi.org/10.5194/egusphere-egu21-11034, 2021.

MAL1a – EGU 2020/2021 Arthur Holmes Medal Lectures

EGU21-16014 | Presentations | MAL1a | Arthur Holmes Medal Lecture 2020

Experimental access to Volcanic Eruptions and their role in the Earth System. 

Donald B. Dingwell

Few things are more central to earth history, planetary evolution and the earth system, than volcanism. Explosive volcanism in particular exhibits individual events whose impact can range from local to global. Developing a mechanistic understanding of the inner workings of volcanic systems is essential for understanding their behavior and modelling their impact. Experiments form a fundamental part of our modern scientific approach to volcanic research, an approach which relies heavily on materials characterisation. In the year 2021, we can look back on decades of  novel and highly innovative experimental approaches applied to the investigation of volcanic processes. The focus has ranged from pre-eruptive and eruptive dynamics  all the way to the fate  and importance of volcanic materials in the Earth System. The applied aspects of the work reach, for example, into eruption forecasting, hazard mapping and aviation safety. I will attempt portray the the long term strategy of the approach we have taken as well as providing comments on the likelihood of certain further developments in the near future.

How to cite: Dingwell, D. B.: Experimental access to Volcanic Eruptions and their role in the Earth System. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16014, https://doi.org/10.5194/egusphere-egu21-16014, 2021.

EGU21-594 | Presentations | MAL1a | Arthur Holmes Medal Lecture 2021

Lithospheric deformation and mantle convection, a geological approach

Laurent Jolivet
Whether the deformation of continents is entirely caused by stresses transmitted from plate boundaries horizontally through the lithospheric stress-guide or also by viscous coupling with the asthenosphere flowing underneath, which was part of Arthur Holmes’ early vision,  is a long-standing question. An increasing amount of observations suggests an efficient coupling between mantle flow and crustal deformation far from plate boundaries, tipping the scale toward the second option. Modern seismic reflection profiles probing the entire crust down to the Moho show asymmetrical features implying simple shear at crustal scale in compressional (mountain belts) and extensional (rifts and passive margins) contexts. Comparison of crustal-scale strain field with seismic anisotropy in strongly extended regions shows homoaxiality of crustal and mantle deformation in continental rifts and back-arc regions. 2-D and 3-D numerical models show that the flow of mantle underneath these regions is faster than in the crust and drives crustal deformation. Beside seismic tomography that images ancient slabs preserved as velocity anomalies in the deep mantle but does not provide any information on the timing, the geological history of basins and orogens, although indirectly, is the only record of past mantle convection. Looking for evidence of coupling between the tectonic history of wide regions and mantle convection in parallel with numerical modelling can provide clues on how convection drives crustal deformation. The recent evolution of numerical modelling, with high-resolution 3-D experiments, can now match the first order of regional models based on geological observations, including the timing and the sequence of events, which are both crucial elements of geological models. This will allow testing complex conceptual models that have been discussed for long. In this lecture, I review different contexts where these questions are debated. Among these contexts complex in 3-D where the geological data set is abundant, the Mediterranean and the Middle East allow discussing the respective contributions of whole-mantle convection involving large plumes vs more local convection in the upper mantle due to slab dynamics in crustal deformation. Studying the dynamics of the India-Asia collision, and the respective roles of lithospheric-scale indentation on the one hand and asthenospheric flow due to slab retreat on the Pacific rim and to large-scale plumes, on the other hand, is also likely to bring interesting insights on how deformation propagates within continents at long distance from plate boundaries.

How to cite: Jolivet, L.: Lithospheric deformation and mantle convection, a geological approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-594, https://doi.org/10.5194/egusphere-egu21-594, 2021.

MAL1b – EGU 2020/2021 Alfred Wegener Medal Lectures

EGU21-4268 | Presentations | MAL1b | Alfred Wegener Medal Lecture 2020

Radiocarbon in modern carbon cycle research

Ingeborg Levin

Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 1028 atoms or about 0.6 tons of radiocarbon (14C), leading to a doubling of the 14C/C ratio in tropospheric CO2 of the Northern Hemisphere, has generated a prominent spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced 14C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO2 into the atmosphere has become the dominant driver of the 14C/C ratio in global atmospheric CO2. The observed decreasing 14C/C trend in atmospheric CO2 may thus help scrutinising the total global release of fossil fuel CO2 into the atmosphere. On the local and regional scale, atmospheric 14C/C measurements are already routinely conducted to separate fossil fuel from biogenic CO2 signals and to estimate trends of regional fossil fuel CO2 emissions. Some prominent examples where the bomb 14CO2 disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.

How to cite: Levin, I.: Radiocarbon in modern carbon cycle research, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4268, https://doi.org/10.5194/egusphere-egu21-4268, 2021.

EGU21-2793 | Presentations | MAL1b | Alfred Wegener Medal Lecture 2021

Plants and river morphodynamics

Angela Gurnell

Research within the field of fluvial biogeomorphology focuses on the impact of organisms, particularly plants, on physical processes and landform development within river environments. This research field has evolved and matured over 50 years such that strong links between plants and river morphodynamics are now established and are increasingly becoming embedded in river management practices.

In this presentation, I provide a personal perspective on the evolution of fluvial biogeomorphology, emphasising five parallel research themes that were initiated in different decades. Research within these themes continues and combines to underpin our current state of knowledge:

The 1970s       Natural vegetation colonises areas according to the degree of river disturbance such that certain plant communities are associated with particular river landforms.

The 1980s       Dead wood pieces influence river morphodynamics and support the development of particular assemblages of physical habitats.

The 1990s       Some large wood sprouts: dead and living trees drive a geomorphological continuum.

The 2000s       River and riparian forest dynamics are linked: field observations, laboratory experiments and numerical models converge.

The 2010s       Many riparian and aquatic plant species can act as river engineers: local engineer species reflect the environmental setting.

2020 onwards    Increasing integration: understanding how interactions between plants and rivers adjust with changes in the biogeographical setting, plant species pool and river energy.

How to cite: Gurnell, A.: Plants and river morphodynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2793, https://doi.org/10.5194/egusphere-egu21-2793, 2021.

MAL1c – EGU 2020/2021 Jean Dominique Cassini Medal Lectures & PS/ST Arne Richter Award for Outstanding ECS Lectures

EGU21-16440 | Presentations | MAL1c | Jean Dominique Cassini Medal Lecture 2020

Organic chemistry in space and the search for life in our Solar System 

Pascale Ehrenfreund

One of the most fascinating questions in planetary science is how life originated on Earth and whether life exists beyond Earth. Life on Earth originated approximately 3.5 billion years ago and has adapted to nearly every explored environment including the deep ocean, dry deserts and ice continents. What were the chemical raw materials available for life to develop? Many carbonaceous compounds are identified by astronomical observations in our Solar System and beyond. Small Solar System bodies hold clues to both processes that formed our Solar System and the processes that probably contributed carbonaceous molecules and volatiles during the heavy bombardment phase to the young planets in our Solar System. The latter process may have contributed to life’s origin on Earth. Space missions that investigate the composition of comets and asteroids and in particular their organic content provide major opportunities to determine the prebiotic reservoirs that were available to early Earth and Mars. Recently, the Comet rendezvous mission Rosetta has monitored the evolution of comet 67P/Churyumov-Gerasimenko during its approach to the Sun. Rosetta observed numerous volatiles and complex organic compounds on the cometary surface and in the coma. JAXA’s Hayabusa-2 mission has returned samples from near-Earth asteroid Ryugu in December 2020 and we may have some interesting scientific results soon. Hayabusa-2 also carried the German-French landing module MASCOT (mobile asteroid surface scout) that provided new insights into the structure and composition of the asteroid Ryugu during its 17-hour scientific exploration.

Presently, a fleet of robotic space missions target planets and moons in order to assess their habitability and to seek biosignatures of simple extraterrestrial life beyond Earth. Prime future targets in the outer Solar System include moons that may harbor internal oceans such as Europa, Enceladus, and Titan. Life may have emerged during habitable periods on Mars and evidence of life may still be preserved in the subsurface, evaporite deposits, caves, or polar regions. On Mars, a combination of solar ultraviolet radiation and oxidation processes are destructive to organic material and life on and close to the surface. However, the progress and the revolutionary quality and quantity of data on “extreme life” on Earth has transformed our view of habitability. In 2021, we will hopefully have three robotic missions arriving at Mars from China, the United Arab Emirates and NASA (Tianwen-1, Hope, and Mars2020 respectively). In 2022, ESA’s ExoMars program will launch the Rosalind Franklin Rover and landing platform, and drill two meters deep into the Martian subsurface for the first time. Mars is still the central object of interest for habitability studies and life detection beyond Earth, paving the way for returned samples and human exploration.

Measurements from laboratory, field, and space simulations are vital in the preparation phase for future planetary exploration missions. This Cassini lecture will review the evolution and distribution of organic matter in space, including results from space missions, field and laboratory research, and discuss the science and technology preparation necessary for robotic and human exploration efforts investigating habitability and biosignatures in our Solar System.

How to cite: Ehrenfreund, P.: Organic chemistry in space and the search for life in our Solar System , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16440, https://doi.org/10.5194/egusphere-egu21-16440, 2021.

EGU21-5084 | Presentations | MAL1c | Arne Richter Award for Outstanding ECS Lecture 2020

Mars’ ionosphere: from our current knowledge to the way forward

Beatriz Sanchez-Cano

The ionosphere of Mars is the conducting layer embedded within the thermosphere and exosphere that is mostly the result of solar EUV photoionization. It is also the layer that links the neutral atmosphere with space, and acts as the main obstacle to the solar wind. The ionosphere’s interaction with the solar wind is a critical aspect that determines the Martian atmospheric evolution, and ultimately the planet’s habitability. This interaction is often referred to as planetary Space Weather, the forecast of which is currently challenging due to the lack of a permanent in-situ solar wind monitor at Mars. Understanding the ionospheric response to solar wind variability is, therefore, essential in order to assess the response of the Martian plasma environment to the dissipation of energy from solar storms, and their impact on current technology deployed on the red planet.

This lecture will focus on our current knowledge of the Martian ionosphere. In particular, I will focus on our recent advances in the understanding of the Martian ionospheric reaction to different Space Weather events during the solar cycle, both from the data analysis and ionospheric modelling perspectives. Some important aspects to consider are the bow shock, magnetic pileup boundary, and ionopause characterization, as well as the behaviour of the topside and bottomside of the ionosphere taking into account the planet’s orbital eccentricity. Moreover, I will show the effect of electron precipitation from large Space Weather events in the very low Martian ionosphere, a region that it is not accessible to in-situ spacecraft observations. Finally, I will conclude the presentation by giving my perspective on some of the key outstanding questions that remain unknown, and I consider they constitute the next generation of Mars’ ionospheric science and exploration.

 

How to cite: Sanchez-Cano, B.: Mars’ ionosphere: from our current knowledge to the way forward, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5084, https://doi.org/10.5194/egusphere-egu21-5084, 2021.

EGU21-6488 | Presentations | MAL1c | Jean Dominique Cassini Medal Lecture 2021

The Science of Space Weather: From Bit Flips to Exoplanets

Janet G Luhmann

While the term ‘space weather’ remains to some synonymous with operational anomalies on spacecraft, communications interruptions, and other practical matters, its broader implications extend across the EGU and beyond. Much of the science underlying space weather has to do with how our star, the Sun, affects the space environment at Earth’s orbit. We are lucky to be living at a time where information from both remote sensing (especially imaging at visible, x-ray and EUV wavelengths) and in-situ measurements (of plasmas, magnetic fields, and energetic particles) have provided unprecedented pictures of the Sun and knowledge of its extended atmosphere, the solar wind. Building on early forays into interplanetary space and deployments of coronagraphs with the Helios and SMM missions in the 70s and 80s, the Ulysses mission reconnaissance far above the ecliptic and the launch of Yohkoh’s and SOHO’s imagers in the 90s, and the long-term ‘monitoring’ of both the Sun and the conditions upstream of the Earth on SOHO, WIND and ACE, the STEREO mission opened a floodgate to research focused on solar activity and its heliospheric and terrestrial consequences. Physics-based, often semi-empirical 3D models increasingly came into widespread use for reconstructing and interpreting the multiple imaging perspectives and multipoint in-situ measurements that the twin STEREO spacecraft, combined with Earth-viewpoint assets (including the GONG ground-based network, and as of 2010, SDO magnetographs), provided on a regular basis. These observations and models together transformed perceptions of phenomena ranging from coronal structure to solar wind sources to eruptive phenomena and consequences, and the tools used to study and forecast them. Now Parker Solar Probe and Solar Orbiter are probing details of the still unexplored regions closer to the Sun than Mercury’s orbit, with the goal of completing that part of the solar/solar wind connection puzzle. And the overall science results from these observations and analysis efforts have not been confined to heliophysics, having especially influenced planetary science and astrophysics. They are seen in recreations of long-past scenarios when our Sun and solar system were evolving, in investigations of solar activity impacts including auroral emissions at the planets,  and in applications to distant planetary systems around other ‘Suns’. That these lofty implications are related to the bit flips and static ‘noise’ first identified with ‘space weather’, provides one of the interesting connections, and still ongoing journeys/stories, within EGU’s research universe.

How to cite: Luhmann, J. G.: The Science of Space Weather: From Bit Flips to Exoplanets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6488, https://doi.org/10.5194/egusphere-egu21-6488, 2021.

EGU21-463 | Presentations | MAL1c | Arne Richter Award for Outstanding ECS Lecture 2021

Utilizing galactic cosmic rays as signatures of coronal mass ejections

Mateja Dumbovic

Coronal mass ejections (CMEs) are the most violent eruptions in the solar system. They are one of the main drivers of the heliospheric variability and cause various interplanetary as well as planetary disturbances. One of their very common in-situ signatures are short-term reductions in the galactic cosmic ray (GCR) flux (i.e. Forbush decreases), which are measured by ground-based instruments at Earth and Mars, as well as various spacecraft throughout the heliosphere (most recently by Solar Orbiter). In general, interplanetary magnetic structures interact with GCRs producing depressions in the GCR flux. Therefore, different types of interplanetary magnetic structures cause different types of GCR depressions, allowing us to distinguish between them. In the interplanetary space the CME typically consists of two structures: the presumably closed flux rope and the shock/sheath which is formed ahead of the flux rope as it propagates and expands in the interplanetary space. Interaction of GCRs with these two structures is modelled separately, where the flux-rope related Forbush decrease can be modelled assuming that the GCRs diffuse slowly into the expanding flux rope, which is initially empty at its center (ForbMod model). The resulting Forbush decrease at a given time, i.e. heliospheric distance, reflects the evolutionary properties of CMEs. However, ForbMod is not yet able to take into account complex, non-self-similar evolution of the flux rope. Nevertheless, Forbush decreases can undoubtedly give us information on the CMEs in the heliosphere, especially where other measurements are lacking, and with further development, Forbush decrease reverse modelling could provide insight into the CME evolution.

How to cite: Dumbovic, M.: Utilizing galactic cosmic rays as signatures of coronal mass ejections, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-463, https://doi.org/10.5194/egusphere-egu21-463, 2021.

MAL1d – EGU 2020/2021 Alexander von Humboldt Medal Lectures

EGU21-9071 | Presentations | MAL1d | Alexander von Humboldt Medal Lecture 2020

Coupling Human - Earth Systems for Sustainability

Bojie Fu

Coupling Human - Earth Systems for Sustainability

 Bojie Fu

(State Key Lab of Urban and Regional Ecology, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

Faculty of Geographical Science, Beijing Normal University, Beijing, China)

Abstract: Human influence on the natural environment has intensified, and the earth has entered the stage of Anthropocene. Earth surface processes are gradually dominated by human behavior, resulting in numerous resources, disasters and ecological problems. The ecosystem services of 60% are degradation in the world. The one of major challenges facing the world’s people are meeting the needs of people today and in the future, and sustaining atmosphere, water, soil and biological products which provided by ecosystems. We will present how to coupling human-earth system and propose the research priorities. They are: (1) Integrating research on multiple processes of water, soil, air and ecosystem; (2) Cascades of ecosystem structure, functions and services; (3) Feedback mechanisms of natural and social systems; (4) Data, models and simulation of sustainable development;(5) Mechanism, approach and policy of sustainable development. Finally, a case study in the Loess plateau of China, an area suffered from severe soil erosion in the world was taken. The changes in four key ecosystem services including water regulation, soil conservation, carbon sequestration, and grain production were assessed and the trade off among the ecosystem services were analysed under the changing landscapes due to the Chinese government’s implementation of the Grain to Green Program (GTGP). We found that ecosystem services convert significantly. The adaptive management strategy was discussed aiming on restoring and improving the sustainable capability of ecosystems providing services, based on the understanding of structure, function and dynamics of ecosystem.

How to cite: Fu, B.: Coupling Human - Earth Systems for Sustainability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9071, https://doi.org/10.5194/egusphere-egu21-9071, 2021.

EGU21-16439 | Presentations | MAL1d | Alexander von Humboldt Medal Lecture 2021

Alexander von Humboldt’s legacy in Earth System Science

Manfred R. Strecker

In this lecture I will first review some of Alexander von Humboldt’s studies on the importance of vertical and latitudinal temperature gradients and surface processes in the context of mountain building and thereby highlight his seminal contributions to Earth System Science. In a second step I will briefly comment on his influence beyond science, including public outreach and the general public’s Earth science literacy – in the face of fake news and distrust in scientific method and discourse, an issue more timely than ever.

The past decades have witnessed a radical shift in human perception of Earth and nature; climate change and increased competition for natural resources combined with human vulnerability to natural hazards have moved environmentalism from the fringes of public awareness to governmental policies. This shift in awareness was presaged by paradigmatic shifts in Earth Science leading to the modern view of Earth as a dynamic system of interactive physical, chemical and biological processes, and ultimately to establishment of the integrative field of Earth System Science. To a certain extent, this point of view and the realization that research across disciplinary boundaries is important and necessary to understand geoprocesses at a variety of time and length scales and in the context of linkages between the different spheres was already the fundament of Humboldt’s thinking and research philosophy during the first half of the 19th century: "The principal impulse by which I was directed was the earnest endeavor to comprehend the phenomena of physical objects in their general connection, and to represent nature as one great whole." Alexander von Humboldt, Kosmos, I, ch. VII, 1845. Although Humboldt wrote this sentence 176 years ago, it reveals his early recognition of the importance of interdisciplinary and transdisciplinary approaches in science. In this regard Humboldt clearly was ahead of his time and most research areas of modern Earth System Science had already been touched upon by him. From mineralogy, geology, volcanology, stratigraphy and paleontology to climatology, biogeography and geobotany, and oceanography he had addressed many aspects research in an integrative, non-isolationist approach. Although Humboldt published his work very early on in disciplinary journals, he followed a holistic approach in science, where inherent processes, their connections across spheres, and feedbacks between them were addressed. Consequently, he also analyzed the influence of humans on the environment, particularly with regards to changes in microclimate, erosion, and biodiversity. By recognizing these relationships he truly followed an early Earth System Science approach, thus linking the geosphere and the anthroposphere. Interestingly, during his career Humboldt devoted himself increasingly to the transfer of knowledge to the general public, which not only resulted in regular public lectures, but also had a far-reaching influence in the art world. Taken together, Humboldt therefore paved the way for an integrative approach to the exploration of the Earth’s systems beyond disciplinary boundaries, and with a strong commitment to share knowledge and educate the public.

How to cite: Strecker, M. R.: Alexander von Humboldt’s legacy in Earth System Science, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16439, https://doi.org/10.5194/egusphere-egu21-16439, 2021.

MAL2 – AS 2020/2021 Vilhelm Bjerknes Medal Lectures, 2020 Division Outstanding ECS Award Lecture & 2021 Arne Richter Award for Outstanding ECS Lecture

EGU21-7317 | Presentations | MAL2 | AS Division Outstanding ECS Award Lecture 2020

Aerosol-weather-climate interactions in highly polluted regions 

Meng Gao

With rapidly expanding economic and industrial developments and tremendous increases in energy consumption, China and India are facing serious aerosol pollution, posing great threat to human health. Aerosols also modulate the climate and ecosystems via aerosol-cloud-radiation interactions. Yet, the poor understanding of aerosol pollution in Asia and its interactions with climate impedes the design and implementation of effective pollution control measures. Combining atmospheric modeling and observations, we demonstrated that the aerosol interactions with radiation and clouds contributed in important ways to intensification of the aerosol enhancements in North China. We manifested also how assimilation of PM2.5 in winter haze periods can improve model predictions and that these improved predictions can reduce significantly the uncertainties in health impacts and estimates of aerosol radiative forcing. It was also demonstrated that the conditions of the ocean temperature in fall can be effectively used to predict the severity of Indian winter haze, which provides useful implications for pollution control at least a season in advance.

How to cite: Gao, M.: Aerosol-weather-climate interactions in highly polluted regions , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7317, https://doi.org/10.5194/egusphere-egu21-7317, 2021.

EGU21-2998 | Presentations | MAL2 | Arne Richter Award for Outstanding ECS Lecture 2021

Interpreting changes in atmospheric methane using satellite and isotopic ratio measurements

Anita Ganesan

Methane is a potent greenhouse gas with concentrations that are rising in the atmosphere in unexpected ways. Because of its radiative efficiency and because its lifetime in the atmosphere is only around a decade, reducing atmospheric methane concentration is a major component of most pathways designed to meet climate targets. Over the past two decades, observations indicate that there have been substantial changes in the emissions and removal of methane. Yet, years later, we still do not definitively know why methane concentrations plateaued in the 2000s, increased globally after 2007 and then continued to increase at an even faster rate after 2014. This limited understanding impacts our ability to carry out targeted emissions reductions. Here, I discuss two areas of my work in addressing gaps in our knowledge. First, I discuss how high-resolution modeling can extract information from satellite data to quantify long-term changes in emissions and the underlying drivers of these changes. I show that Brazil is a unique example where major sources such as wetlands and cattle are geographically distinct and thus satellite data can be used to examine changes from particular processes. I show how in the absence of this separation, which is the case for many other parts of world, additional information such as isotopic ratios can be used to contribute to the partitioning of methane emissions into underlying sources. I also discuss the limitations in current capability to effectively use isotopic ratio measurements. I show how field experiments and simple models can be used to derive global distributions in the isotopic signatures of major sources such as wetlands, providing more consistency against observations. I discuss how incorrect assumptions about source signature distributions have a major impact on our ability to interpret atmospheric isotopic ratio measurements and that this may be one reason why we have not been able to conclusively interpret the recent atmospheric methane record.

How to cite: Ganesan, A.: Interpreting changes in atmospheric methane using satellite and isotopic ratio measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2998, https://doi.org/10.5194/egusphere-egu21-2998, 2021.

EGU21-8934 | Presentations | MAL2 | Vilhelm Bjerknes Medal Lecture 2020

The Nonlinear Nature of Atmospheric Chemistry

Michael Prather

When scientific or policy-relevant questions involve atmospheric chemistry, one often hears "nonlinear" being invoked, but the precise nature of the nonlinearity is never delineated, and we are left with the fuzzy impression that nonlinear problems are difficult, with no simple answer.  I have even seen it used to avoid including indirect greenhouse gases in the Kyoto Protocol.  For differentiable systems, nonlinear behavior can be expressed through a Taylor expansion whereby any of the 2nd order terms (x2, y2 or xy) are the first nonlinear parts.  In this lecture I explore a range of scientific discoveries or developments in atmospheric chemistry where the nonlinear nature was critical to understanding the problem.  I select a set of problems worked on by many colleagues and myself over the last four decades.  These include:  multiple solutions in stratospheric chemistry; catastrophic depletion of ozone; numerical methods for tracer transport; our developing understanding of methane; chemical feedbacks and indirect greenhouse gases; and finally the rich heterogeneity of gases that drives tropospheric chemistry. I hope to convince you that by recognizing the nonlinear nature of atmospheric chemistry and understanding when it is important and when it is not, we can advance the field.   

How to cite: Prather, M.: The Nonlinear Nature of Atmospheric Chemistry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8934, https://doi.org/10.5194/egusphere-egu21-8934, 2021.

EGU21-565 | Presentations | MAL2 | Vilhelm Bjerknes Medal Lecture 2021

Back to the Future: Reducing Atmospheric Particulate Matter Levels to Improve Human Health

Spyros Pandis

The human development of our planet has a variety of negative impacts on the composition of its atmosphere at every scale – locally, regionally, and even globally. One of these dramatic changes has been the increase in the mass concentrations of sub-micrometer particles by one to sometimes two orders of magnitude over populated areas in the Northern Hemisphere. These atmospheric aerosols can cause serious health problems, reduce visibility, contribute to acidic deposition and material damage, but are also cooling the planet by reflecting sunlight back to space. Atmospheric chemistry occurs within a fabric of complicated atmospheric dynamics and physics. This interplay often results in nonlinear and often counterintuitive changes of the system when anthropogenic emissions change. A major goal of our research has been to gain a predictive understanding of the physical and chemical processes that govern the dynamics, size, and chemical composition of atmospheric aerosols.

To illustrate the advances in the experimental techniques and theoretical tools in atmospheric aerosol science, we will go back to the beginning of the 21st century and we will revisit the design a particulate matter control strategy for the Eastern US based on the data, knowledge, and tools available at that time. We will then look at the effects of the parts of this control strategy that have been materialized and their effects on public health using the current understanding. Finally, we will look forward in ways of further improving air quality in the US and Europe.

How to cite: Pandis, S.: Back to the Future: Reducing Atmospheric Particulate Matter Levels to Improve Human Health, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-565, https://doi.org/10.5194/egusphere-egu21-565, 2021.

MAL3 – BG 2020/2021 Vladimir Ivanovich Vernadsky Medal Lectures, 2020 Division Outstanding ECS Award Lecture & 2021 Arne Richter Award for Outstanding ECS Lecture

EGU21-16152 | Presentations | MAL3 | BG Division Outstanding ECS Award Lecture 2020

The response of deep soil carbon to climate change: From experiments to meta-analysis

Caitlin Pries, Katherine Heckman, Pamela Templer, Serita Frey, and Susan Crow

Over half of global soil organic carbon (SOC) is stored in subsurface soils (>20 cm depth), but the vulnerability of this deeper SOC to climate change has only recently been tested. Most soil warming experiments have either only warmed surface soils or only examined the response of the surface carbon dioxide flux, so the sensitivity of SOC at different soil depths to climate change is undetermined. As predictive models of terrestrial carbon storage move toward more mechanistic representations, we need to understand how the carbon cycle differs across soil depths. We present depth-explicit measurements of soil CO2 production from six studies, including four in situ deep soil warming experiments. The experiments’ locations ranged from coniferous to hardwood temperate forests in the United States to volcanic soils in Hawaii. We have found that in temperate forests, deep soil carbon is just as vulnerable to warming-induced losses as surface soils. However, where minerals are strongly associated with organic carbon, as in Hawaii, or in degraded soils where much of the organic matter has been lost, deep soil carbon resists warming-induced losses. Thus, the response of deep soil to climate change is dependent on its availability to microbes. This conclusion is supported by a worldwide meta-analysis of radiocarbon data among soil density fractions, which found that the amount of carbon in the particulate free light fraction decreased with mean annual temperature, but the carbon in the heavy, mineral-associated fraction did not.

How to cite: Pries, C., Heckman, K., Templer, P., Frey, S., and Crow, S.: The response of deep soil carbon to climate change: From experiments to meta-analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16152, https://doi.org/10.5194/egusphere-egu21-16152, 2021.

EGU21-5126 | Presentations | MAL3 | Arne Richter Award for Outstanding ECS Lecture 2021

The role of inter- and intra-specific variability in controlling trait measurements in tropical forests

Lucy Rowland, Paulo Bittencourt, David Bartholomew, Andre Giles, Rafael Oliveira, Maurizio Mencuccini, Antonio da Costa, Lindsay Banin, David Burslem, and Patrick Meir

Tropical rainforests harbour the greatest diversity of woody plant species in the world. Consequently, within any individual forest plot, replicating functional trait measurements, particularly at species level can be challenging. However, trait variation within and between species can be very large. Limited sampling opportunities in diverse forests poses a huge challenge to understanding the role both inter- and intra-specific variation play when we scale up individual trait measurements to plot or landscape averages. Using data from tropical forests within Latin America and South East Asia, we explore the potential role which inter- and intra-specific variation may play when attempting to compare functional trait values in tropical forests experiencing different environmental conditions. We demonstrate the need for renewed care considering how we construct sampling protocols within these forests for functional trait sampling. This includes considering the size and canopy position of the trees we sample across plots, alongside the number of individual within a species, and the number of species, we sample to generate results concerning how variation in environmental conditions influences plant functional traits. Considering such issues also offers considerable opportunities to advance our knowledge of the processes of acclimation and trait plasticity and how they may influences responses to environmental change. In-turn opening new prospects to better inform vegetation models, particularly individual-based models and therefore to investigate the impact of these properties at larger scales.

How to cite: Rowland, L., Bittencourt, P., Bartholomew, D., Giles, A., Oliveira, R., Mencuccini, M., da Costa, A., Banin, L., Burslem, D., and Meir, P.: The role of inter- and intra-specific variability in controlling trait measurements in tropical forests, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5126, https://doi.org/10.5194/egusphere-egu21-5126, 2021.

EGU21-13298 | Presentations | MAL3 | Vladimir Ivanovich Vernadsky Medal Lecture 2021

Radiocarbon constraints on carbon cycling in plants and soils

Susan Trumbore, Carlos Sierra, Alison Hoyt, Boaz Hilman, Jeffrey Beem-Miller, Shane Stoner, Sophie von Fromm, Zheng Shi, and James Randerson

Tracing ‘bomb’ radiocarbon produced by atmospheric testing of atomic weapons through vegetation and soils provides information of the dynamics of terrestrial carbon cycling on timescales of years to centuries. Processes operating on these timescales are of interest because they regulate key functions in long-lived plants and regulate the potential for increasing soil carbon storage.  However, the multiple pathways taken by carbon transiting ecosystems from photosynthesis to respiration and decomposition complicate the quantitative interpretation of radiocarbon observations.  In the 14Constraint project, we are exploring how to optimize measurements of radiocarbon as well as to improve their interpretation by providing constraints for comparison with models.   This talk will focus on efforts to synthesize global radiocarbon measurements of mean age and transit time, and suggest ways forward to improve process-level understanding.

How to cite: Trumbore, S., Sierra, C., Hoyt, A., Hilman, B., Beem-Miller, J., Stoner, S., von Fromm, S., Shi, Z., and Randerson, J.: Radiocarbon constraints on carbon cycling in plants and soils, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13298, https://doi.org/10.5194/egusphere-egu21-13298, 2021.

EGU21-2365 | Presentations | MAL3 | Vladimir Ivanovich Vernadsky Medal Lecture 2020

Human induced changes in the carbon cycle over the last 60 years

Pierre Friedlingstein

Human activities have an unprecedented impact on the global carbon cycle.  Atmospheric CO2 concentrations have been continuously monitored since 1958, and show a 30% increase, from 315 ppm in 1958 to 412 ppm in 2020. Anthropogenic emissions, primarily from fossil fuel combustion, but also from land-use changes, are the drivers of these changes, with global emissions almost tripling over that period, from 4GtC per year in 1958 to almost 12 GtC per year at present. Although fossil fuel emission declined by about 7% in 2020 due to response to the COVID-19 pandemic, there are no long-term sign of global emissions declining yet, despite climate policies being put in places in many countries.

The atmospheric CO2 increase induces land and ocean carbon uptake, respectively driven by enhanced photosynthesis, leading to larger land biomass and soil carbon; and by enhanced air-sea CO2 exchange, leading to larger carbon content in the surface ocean and export to the deep ocean. These mechanisms are negative feedbacks in the Earth system and are removing about 50% of the CO2 emitted in the atmosphere. Without these land and ocean carbon sinks, current atmospheric CO2 would already be around 600 ppm.

However, modelling studies show that climate change reduces land and ocean carbon sinks, hence amplifying the warming. Although there is agreement that such positive feedback will develop over the course of the century, there are not yet clear evidence of a major climate driven reduction of the carbon sinks.  So far, observations and modelling studies of the historical carbon cycle do not show any sign of a tipping point in the global carbon cycle.

How to cite: Friedlingstein, P.: Human induced changes in the carbon cycle over the last 60 years, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2365, https://doi.org/10.5194/egusphere-egu21-2365, 2021.

MAL4a – CL 2020/2021 Milutin Milankovic Medal Lectures & 2020 Arne Richter Award for Outstanding ECS Lecture

EGU21-11488 | Presentations | MAL4a | Milutin Milankovic Medal Lecture 2020

Astronomical forcing and climate : insights from ice core records

Valérie Masson-Delmotte

Ice cores provide a wealth of insights into past changes in climate and atmospheric composition.

Obtaining information on past polar temperature changes is important to document climate variations beyond instrumental records, and to test our understanding of past climate variations, including the Earth system response to astronomical forcing.

Since the 1960s, major breakthrough in ice core science have delivered a matrix of quantitative Greenland and Antarctic ice core records.

Temperature reconstructions from polar ice cores document past polar amplification, and provide quantitative constraints to test climate models.

Climate information from the air and ice preserved in deep ice cores has been crucial to unveil the tight coupling between the carbon cycle and climate and the role of past changes in atmospheric greenhouse gas composition in the Earth system response to astronomical forcing.

Ice core constraints on past changes in ice sheet topography are also key to characterize the contribution of the Greenland and Antarctic ice sheets to past sea level changes.

The construction of a common chronological framework for Greenland and Antarctic ice core records has unveiled the bipolar sequence of events during the glacial-interglacial cycle, and the interplay between abrupt change and the response of the climate system to astronomical forcing.

International efforts have started to obtain the oldest ice cores (hopefully back to 1,5 million years) from Antarctica, in order to understand the reasons for the major shifts in the response of the climate system to astronomical forcing at that time, leading to more intense and longer glacial periods. 

How to cite: Masson-Delmotte, V.: Astronomical forcing and climate : insights from ice core records, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11488, https://doi.org/10.5194/egusphere-egu21-11488, 2021.

EGU21-16573 | Presentations | MAL4a | Milutin Milankovic Medal Lecture 2021

Dynamical Ice Sheet-Climate System Response to Astronomical Forcing

Ayako Abe-Ouchi

Paleoclimate modelling using simple models, EMICs (Earth System Models of Intermediate Complexity) and GCMs (General Circulation Models) combined with ice sheet models has become a powerful tool for understanding how the long-term climate system with ice sheets responds to external forcings such as Milankovitch forcing. With the aid of supercomputers and advances in climate model development, it is now possible to perform a much larger number of snapshot experiments with fixed forcings as well as transient experiments with evolving forcings. This talk will review the models that simulate the Northern Hemisphere ice sheet change and climate during the ice age cycles and discuss upcoming challenges. The talk will also present recent works on simulating millennial scale climate changes and the link with the ice age cycle. The last termination of the ice age cycles as well as glacial periods were punctuated by abrupt millennial scale climate changes, such as the Bølling-Allerød interstadial, the Younger Dryas and Dansgaard-Oeschger events. Abrupt climate changes have been shown to be strongly linked to changes in the Atlantic Meridional Overturning Circulation (AMOC) and the shift between the (quasi) multiple equilibria of AMOC, but the mechanism behind these abrupt changes and the link to climate change in the orbital scale are not clear. Modelling the stability of AMOC under different climate conditions together with deglacial climate change using fully coupled ocean-atmosphere GCMs has been challenging. Here we present a series of long transient experiments of at least 10,000 years with forcings under different ice sheet sizes, greenhouse gas levels and orbital parameters, as well as deglacial experiments following PMIP4 protocols, using a coupled ocean-atmosphere model, MIROC4m AOGCM. When forcing under glacial condition is applied, even without freshwater perturbation, the climate-ocean system shows self-sustained oscillations within a “sweet spot.” We also see a bipolar seesaw pattern and switching between interstadials and stadials, whose return time ranges from 1,000 years to nearly 10,000 years depending on the background forcing during the ice age cycle. Our transient deglaciation experiment with a gradually changing insolation, greenhouse gas forcing and ice sheet with meltwater from the glacial period to the Holocene is analysed and compared with proxy data as well as with the series of experiments with self-sustained oscillations for a better interpretation. Implications on the role of abrupt climate changes in shaping the longer-term global ice age cycle are further discussed.

How to cite: Abe-Ouchi, A.: Dynamical Ice Sheet-Climate System Response to Astronomical Forcing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16573, https://doi.org/10.5194/egusphere-egu21-16573, 2021.

EGU21-207 | Presentations | MAL4a | Arne Richter Award for Outstanding ECS Lecture 2020

Making informed use of observations and climate models to advance understanding of past and future sea ice changes

Francois Massonnet

Polar Regions are viewed by many as "observational deserts", as in-situ measurements there are indeed scarce relative to other regions. The increasing availability of satellite observations does not entirely solve the problem, due to persistent uncertainties in the derived products. Climate models have been instrumental in completing the big picture, but they are themselves subject to errors, some of which are systematic. How to take advantage of the respective strengths of observations and models, while minimizing their respective weaknesses?  To illustrate this point, I will discuss how recent advances in data assimilation, model evaluation, and numerical modeling have enabled progress on addressing important questions in polar research, such as: what are the causes of the recent Antarctic sea ice variability? What might the future of Arctic sea ice look like? How to improve the skill of seasonal sea ice predictions? How should the existing observational network be improved at high latitudes? What are the priorities in terms of modeling? By running through these cases, I will provide support for the emerging hypothesis that "the whole is greater than the sum of its parts": treating observations and climate models as two noisy instances of the same, unknown truth, gives access to answers that would not have been possible using each source separately.

How to cite: Massonnet, F.: Making informed use of observations and climate models to advance understanding of past and future sea ice changes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-207, https://doi.org/10.5194/egusphere-egu21-207, 2021.

MAL4b – CL 2020/2021 Hans Oeschger Medal Lectures & Division Outstanding ECS Award Lecture

EGU21-16571 | Presentations | MAL4b | Hans Oeschger Medal Lecture 2020

(Paleo)climate science for the 21st century

Kim M. Cobb

Records of past climate trends, variability, and extremes hold key insights into Earth’s changing climate, yet their full potential will remain untapped without a concerted effort to surmount several critical challenges, some time-sensitive.  In a century defined by accelerating climate change and human disturbance, the climate archive itself is at grave risk given that i) many paleoclimate records end in the late 20th century, with no concerted effort to extend them to the present-day, and ii) many paleoclimate archives are disappearing under pressure from climate change and/or human disturbance. Second, many paleoclimate records are comprised of oxygen isotopes, yet the coordinated, multi-scale observational and modeling infrastructures required to unravel the mechanisms governing water isotope variability are as yet underdeveloped. This dramatic oversight exists despite development of technologies that avoid costly analysis via mass spectrometers, and despite the fact that water isotopes may very well be one of the most powerful diagnostic tracers of a changing global water cycle. Lastly, in part owing to the aforementioned deficiencies, paleoclimate data assimilation efforts remain fraught with large uncertainties, despite their promise in constraining many of the most uncertain aspects of future climate impacts, including the evolution of extreme events and hydrological trends and variability. Climate science for the 21st century requires deep investments in the full integration of paleoclimate data and approaches into frameworks for climate risk and hazard assessments. In this sense, it is not surprising that paleoclimate scientists have played a key role in the communication of climate change science to decision-makers and the general public alike. Their understanding of the Earth system also equips them to contribute valuable insights to teams comprised of researchers, practitioners, and  decision-makers charged with leveraging science to inform solutions, in service to society. It’s time to recognize that all climate scientists study climate of the past, and all paleoclimate scientists have insights that are relevant to our climate future.

How to cite: Cobb, K. M.: (Paleo)climate science for the 21st century, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16571, https://doi.org/10.5194/egusphere-egu21-16571, 2021.

EGU21-15772 | Presentations | MAL4b | Hans Oeschger Medal Lecture 2021

Understanding and predicting climate extremes on land: The new frontier

Sonia Seneviratne

We live on land and are daily affected by land climate variations, but early climate pioneers often focused on ocean-climate interactions and ice-covered regions. With good reasons, since oceans cover two third of the Earth and are thus critical for the global climate, and because ice sheets have strongly varied over millennia and include key indices on past climate. However, recent research has increasingly shown that land climate, where we live, displays specific climate characteristics, which cannot be simply inferred from global climate responses. This is particularly the case for climate extremes, such as heatwaves and droughts. I will present recent evidence for these properties and some avenues for future research.

Land-climate interactions, which are modulated by vegetation, play a key role for climate variability on continents. This implies a fascinating interface between biological processes and climate physics. The limitation of water on continents, and the role of vegetation in the land water input to the atmosphere, implies very different water-cycle responses compared to what is seen on oceans: For instance, dry regions do not necessarily get drier, nor wet regions wetter under increasing greenhouse gas forcing. In addition, land climate can strongly deviate from global climate in other ways: During the so-called “hiatus period” in the early 2000s, changes in temperature extremes on land actually showed an amplified increase. Furthermore, key land processes are still insufficiently captured in state-of-the art Earth System Models (ESMs), such as land water effects on the global carbon cycle, and climate response to irrigation or land management.

Land processes are playing an increasingly central role in the development of pathways for climate mitigation consistent with the aims of the Paris Agreement, for instance related to afforestation or the development of bioenergy use in combination with carbon capture and storage. However, these scenarios often overlook biological and physical constraints for these land cover and land use changes, such as risks from climate extremes, including fire, in a warming world. ESM emulators for grid-cell responses may help to proof such scenarios in the needed rapid and safe transition to a net-zero COworld.

How to cite: Seneviratne, S.: Understanding and predicting climate extremes on land: The new frontier, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15772, https://doi.org/10.5194/egusphere-egu21-15772, 2021.

EGU21-4761 | Presentations | MAL4b | CL Division Outstanding ECS Award Lecture 2021

A coupled multi-proxy and process modelling approach for extraction of quantitative terrestrial ecosystem information from speleothems

Franziska Lechleitner, Christopher C. Day, Oliver Kost, Micah Wilhelm, Negar Haghipour, Gideon M. Henderson, and Heather M. Stoll

Terrestrial ecosystems are intimately linked with the global climate system, but their response to ongoing and future anthropogenic climate change remains poorly understood. Reconstructing the response of terrestrial ecosystem processes over past periods of rapid and substantial climate change can serve as a tool to better constrain the sensitivity in the ecosystem-climate response.

In this talk, we will present a new reconstruction of soil respiration in the temperate region of Western Europe based on speleothem carbon isotopes (δ13C). Soil respiration remains poorly constrained over past climatic transitions, but is critical for understanding the global carbon cycle and its response to ongoing anthropogenic warming. Our study builds upon two decades of speleothem research in Western Europe, which has shown clear correlation between δ13C and regional temperature reconstructions during the last glacial and the deglaciation, with exceptional regional coherency in timing, amplitude, and absolute δ13C variation. By combining innovative multi-proxy geochemical analysis (δ13C, Ca isotopes, and radiocarbon) on three speleothems from Northern Spain, and quantitative forward modelling of processes in soil, karst, and cave, we show how deglacial variability in speleothem δ13C is best explained by increasing soil respiration. Our study is the first to quantify and remove the effects of prior calcite precipitation (PCP, using Ca isotopes) and bedrock dissolution (open vs closed system, using the radiocarbon reservoir effect) from the speleothem δ13C signal to derive changes in respired δ13C over time. Our approach allows us to estimate the temperature sensitivity of soil respiration (Q10), which is higher than current measurements, suggesting that part of the speleothem signal may be related to a change in the composition of the soil respired δ13C. This is likely related to changing substrate through increasing contribution from vegetation biomass with the onset of the Holocene.

These results highlight the exciting possibilities speleothems offer as a coupled archive for quantitative proxy-based reconstructions of climate and ecosystem conditions.

How to cite: Lechleitner, F., Day, C. C., Kost, O., Wilhelm, M., Haghipour, N., Henderson, G. M., and Stoll, H. M.: A coupled multi-proxy and process modelling approach for extraction of quantitative terrestrial ecosystem information from speleothems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4761, https://doi.org/10.5194/egusphere-egu21-4761, 2021.

MAL5 – CR 2021 Julia and Johannes Weertman Medal Lecture & 2020/2021 Division Outstanding ECS Award Lectures

EGU21-16570 | Presentations | MAL5 | CR Division Outstanding ECS Award Lecture 2020

Draining and Filling of an Interconnected Sub-glacial Lake Network in East Antarctica

Anna Hogg, Noel Gourmelen, Richard Rigby, and Thomas Slater

The Antarctic Ice sheet is a key component of the Earth system, impacting on global sea level, ocean circulation and atmospheric processes. Meltwater is generated at the ice sheet base primarily by geothermal heating and friction associated with ice flow, and this feeds a vast network of lakes and rivers creating a unique hydrological environment. Subglacial lakes play a fundamental role in the Antarctic ice sheet hydrological system because outbursts from ‘active’ lakes can trigger, (i) change in ice speed, (ii) a burst of freshwater input into the ocean which generates buoyant meltwater plumes, and (iii) evolution of glacial landforms and sub-glacial habitats. Despite the key role that sub-glacial hydrology plays on the ice sheet environment, there are limited observations of repeat sub-glacial lake activity resulting in poor knowledge of the timing and frequency of these events. Even rarer are examples of interconnected lake activity, where the draining of one lake triggers filling of another. Observations of this nature help us better characterise these events and the impact they may have on Antarctica’s hydrological budget, and will advance our knowledge of the physical mechanism responsible for triggering this activity. In this study we analyse 9-years of CryoSat-2 radar altimetry data, to investigate a newly identified sub-glacial network in the Amery basin, East Antarctica. CryoSat-2 data was processed in ‘swath mode’, increasing the density of elevation measurements across the study area. The plane fit method was employed in 500 m by 500 m grid cells, to measure surface elevation change at relatively high spatial resolution. We identified a network of 10 active subglacial lakes in the Amery basin. 7 of these lakes, located below Lambert Glacier, show interconnected hydrological behaviour, with filling and drainage events throughout the study period. We observed ice surface height change of up to 6 meters on multiple lakes, and these observations were validated by independently acquired TanDEM-X DEM differencing. This case study is an important decade long record of hydrological activity beneath the Antarctic Ice Sheet which demonstrates the importance of high resolution swath mode measurements. In the future the Lambert lake network will be used to better understand the filling and draining life cycle of sub-glacial hydrological activity under the Antarctic Ice Sheet.

How to cite: Hogg, A., Gourmelen, N., Rigby, R., and Slater, T.: Draining and Filling of an Interconnected Sub-glacial Lake Network in East Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16570, https://doi.org/10.5194/egusphere-egu21-16570, 2021.

EGU21-2776 | Presentations | MAL5 | CR Division Outstanding ECS Award Lecture 2021

The Marine Geophysical Record of Past Ice Sheets

Christine Batchelor

An understanding of the former configuration and dynamics of ice sheets is essential to constrain numerical models of past environmental conditions and predict the likely future responses of ice sheets to climate change. Evidence of past ice-sheet activity is often well-preserved on and beneath the seafloor of glaciated continental margins, where it can be analysed using a variety of marine geophysical techniques. In this presentation, I will describe how marine geophysical data can be used to investigate former ice-sheet behaviour at different temporal scales, drawing on recent examples from my research. First, 2D and 3D seismic data show how mid- and high-latitude continental margins have been shaped by the repeated advance and retreat of ice sheets during the last three million years. Secondly, bathymetric data enable the interpretation of glacial landforms preserved on the seafloor, revealing the dynamic behaviour of ice masses since the Last Glacial Maximum. Finally, the recent application of autonomous underwater vehicles to acquire high-resolution geophysical data provides a step-change in our ability to image submarine landforms and facilitates new interpretations about ice dynamics at fine temporal and spatial scales.

How to cite: Batchelor, C.: The Marine Geophysical Record of Past Ice Sheets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2776, https://doi.org/10.5194/egusphere-egu21-2776, 2021.

EGU21-16360 | Presentations | MAL5 | Highlight | Julia and Johannes Weertman Medal Lecture 2021

Glacier biogeochemistry: from Haut Glacier d’Arolla to the Antarctic and Greenland Ice Sheets

Martyn Tranter

Glacier biogeochemistry grew out of hydrochemical studies of water movement through small valley glaciers in the 1970’s into modern studies of ice sheet runoff and ice berg fertilisation of the oceans. This talk will briefly review how this happened, and then look at the current research agenda with a view to identifying research needs and future research directions. Research on subglacial lakes, nutrient export to the oceans, biological ice sheet darkening and the production of bioavialable, yet ancient, dissolved organic carbon on glaciers will be covered. Finally, when you think you know it all, a new process fundamental process turns up. Recent work on the release and production of bioavailable chemicals by glacier erosion will be highlighted, including the significance of the this work in the search for life beyound Earth.  

How to cite: Tranter, M.: Glacier biogeochemistry: from Haut Glacier d’Arolla to the Antarctic and Greenland Ice Sheets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16360, https://doi.org/10.5194/egusphere-egu21-16360, 2021.

MAL6a – EMRP 2020 Louis Néel Medal Lecture & 2021 Division Outstanding ECS Award Lecture

EGU21-8520 | Presentations | MAL6a | Louis Néel Medal Lecture 2020

New Constraints on Fault Nucleation and Propagation Using Dynamic Microtomography Experiments

Wen-lu Zhu

Experimental rock deformation research plays an important role in understanding the mechanical behavior, deformation microstructures, and physical properties of rocks and minerals. In practice, most experiments are designed to isolate a given process, limiting access to the interplay between various processes that takes place in nature. This is in part because changes in microstructure are commonly documented after an experiment has ended. The loss of information during deformation makes quantifying feedback of different mechanisms extremely challenging. However, natural processes often involve concurrent inelastic deformation mechanisms and simultaneous metamorphic or diagenetic reactions. Quantitative accessment of these processes demands better constraints of the feedback between rock deformation and the evolving rock properties and microstructures.

Recent dynamic microtomography experiments have shown great potential in characterizing the evolution of microstructure and strain distribution during fault growth at in-situ pressure and temperature conditions. Using an X-ray transparent deformation apparatus that operates at crustal stress conditions, we have imaged the process of fault nucleation and propagation in natural rocks undergoing brittle faulting.  Applying the digital volume correlation technique to time-resolved 3-dimensional microtomographic datasets, we documented the evolution of strain distribution within a deforming rock. These results elucidate how fractures open, slide, coalesce, and propagate in rock samples responding to increasing shear stress.  

Using dynamic microtomography, it is now possible to address the effect of chemo-mechanical coupling on the emergent properties of rocks by conducting deformation experiments in which several mechanisms operate simultaneously. We studied the effect of chemo-mechanical coupling on fracturing induced by hydration reaction in serpentinite. Quantitative characterization of evolving mechanical behavior and microstructure enables us to understanding the feedback between thermal load, chemical reaction rate, and mechanical failure. Dynamic microtomography provides a promising approach to link evolving mechanical behavior with evolving microstructures. New experimental constraints on microstructural and internal stress-strain evolution can lead to more robust extrapolations of laboratory results to large scale geologic processes.

How to cite: Zhu, W.: New Constraints on Fault Nucleation and Propagation Using Dynamic Microtomography Experiments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8520, https://doi.org/10.5194/egusphere-egu21-8520, 2021.

EGU21-9725 | Presentations | MAL6a | EMRP Division Outstanding ECS Award Lecture 2021

The dynamics of earthquakes rupture : A view from the laboratory

Francois Passelegue, Federica Paglialunga, Alexandre Schubnel, and Giulio Di Toro

 

Earthquakes are spectacular natural disasters, with for example the recent disastrous Sumatra and Tohoku-Oki earthquakes (2004 and 2011, respectively). Presently, predicting earthquakes remains one of the biggest societal challenges in natural science. While seismological observations have much improved in recent years, our understanding of earthquake source physics remains limited due to the scarcity of monitored seismic rupture along similar fault systems, making long- or short-time scale predictions impossible. Friction and fracture are the two keys to understanding earthquakes. Laboratory experiments could be a robust solution to study earthquakes under safe and controlled conditions, which is mandatory to understand and compare the details of earthquake source physics. Conversely to common friction experiments conducted at both slow and seismic slip rates, the stick-slip mechanism is associated to the propagation of a rupture front, i.e. the radiation of seismic waves. Using stick-slip as an earthquake analog coupled to a state-of-the-art high frequency acoustic monitoring system, we demonstrated in the past that accelerations recorded in the kilohertz range on centimeter-sized samples were self-similar to the ones one can expect at the kilometric scale for a large earthquake. Based on this laboratory earthquakes catalogue, we highlighted that acoustic and strain measurements can be used to (i) locate and follow seismicity, (ii) estimate the energy budget of laboratory earthquakes, (iii) discriminate the mode of slip and the rupture speed. Lately, using medium scale experiments, we studied the scale dependence of rupture processes. These new results, notably in term of weakening of faulting and energy balance allowed us to initiate a bridge between laboratory earthquakes, fracture mechanics and natural seismicity. We discuss here how these experimental results can be upscaled to natural earthquakes.

How to cite: Passelegue, F., Paglialunga, F., Schubnel, A., and Di Toro, G.: The dynamics of earthquakes rupture : A view from the laboratory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9725, https://doi.org/10.5194/egusphere-egu21-9725, 2021.

MAL6b – EMRP 2020 & 2021 Petrus Peregrinus Medal Lectures

EGU21-16330 | Presentations | MAL6b | Petrus Peregrinus Medal Lecture 2020

Early humans in East Asia: Insights into climatic influence on human evolution

Rixiang Zhu

East Asia is a key area for probing into the interplay between Quaternary climate change and human adaptations to diverse terrestrial ecosystems. Integrated chronology based mainly on high-resolution magnetostratigraphy in conjunction with detailed biostratigraphy and high-precision isotopic dating of early humans and Paleolithic stone tools in mainland East Asia, western and southeastern Asia has provided insights into our understanding of climatic influence on human evolution in a variety of environments in the eastern Old World. For example, there is a prominent geographic expansion for early humans from low southern latitudes (e.g., tropical SE Asia and subtropical Yuanmou Basin and Bose Basin), through middle latitudes, to high northern latitudes (e.g., the Nihewan Basin). Especially, increased toolmaking skills and technological innovations are evident in temperate Nihewan Basin at the onset of the Mid-Pleistocene Climate Transition. The improved ability to adjust to diverse environments for early humans in East Asia has contributed to better understanding how climate change has shaped early human evolution.

How to cite: Zhu, R.: Early humans in East Asia: Insights into climatic influence on human evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16330, https://doi.org/10.5194/egusphere-egu21-16330, 2021.

EGU21-522 | Presentations | MAL6b | Petrus Peregrinus Medal Lecture 2021

High-Resolution Chronostratigraphy for Sedimentary Rocks using Rock Magnetics

Kenneth Kodama

Rock magnetics can be used to identify orbitally-forced global climate cycles in sedimentary rock sequences. The identification of Milankovitch cycles with nominal periods of 20, 40, 100 and 400 ka can be used to construct a high-resolution chronostratigraphy for a rock sequence that can have a variety of important geologic applications. Several examples will be presented. The rock magnetic cyclostratigraphy of Eocene marine, deltaic mudstones and marls of the Arguis Formation illustrates how rock magnetics can be used to determine the deformation rates of a salt tectonics growth fold in the Pyrenees. The duration of the Ediacaran Shuram carbon-isotope excursion was determined to be 8-9 Ma from rock magnetic cyclostratigraphy studies of marine rocks from Death Valley, California (Rainstorm member of the Johnnie Formation), southern Australia (Wonoka Formation), and in central and southern China (Doushantuo Formation).  Further cyclostratigraphic study of the Rainstorm member in the Desert Range, Nevada, allowed the construction of a high-resolution magnetostratigraphy by combining and calibrating magnetostratigraphic results from Death Valley and Nevada to reveal a high reversal rate of 12.7 reversals/Ma in the Ediacaran. More detailed study of the Doushantuo Formation at Huangliaba, China indicated that even though its ferromagnetic minerals were predominately secondary pyrrhotite, magnetic susceptibility measurements could still detect a depositional, orbitally-forced cyclostratigraphy carried by paramagnetic minerals. Finally, the Carboniferous Mauch Chunk Formation red beds from Pottsville, Pennsylvania yielded a magnetic susceptibility cyclostratigraphy in terrestrial, fluvial sediments despite their discontinuous sedimentation. This study showed that both portable susceptibility meter measurements and lab-based measurement of rock samples could discern the same period cycles. Detailed low and high temperature magnetic susceptibility measurements indicate that the ferromagnetic mineral hematite, rather than paramagnetic clays, is the predominant carrier of the orbitally-forced global climate signal. All these studies show the power of rock magnetics for constructing a high-resolution chronostratigraphy for sedimentary rock sequences.

How to cite: Kodama, K.: High-Resolution Chronostratigraphy for Sedimentary Rocks using Rock Magnetics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-522, https://doi.org/10.5194/egusphere-egu21-522, 2021.

MAL7 – ERE 2020/2021 Division Outstanding ECS Award Lectures

Underground pumped storage hydropower (UPSH) is an alternative energy storage system (ESS) for flat regions, where conventional pumped storage hydropower plants cannot be constructed due to topographical limitations. UPSH plants consist in two reservoirs, the upper one is located at the surface or possibly underground (but at shallow depth) while the lower one is underground. Although the underground reservoir can be drilled, the use of abandoned mines (deep or open pit mines) as underground reservoir is a more efficient alternative that is also beneficial for local communities after the cessation of mining activities. Given that mines are rarely waterproofed, water exchanges between UPSH plants and the underground medium are expected. Water exchanges may have negative consequences for the environment, but also for the feasibility of UPSH plants. The impacts on the environment and the plant efficiency may have hydraulic (changes of the natural piezometric head distribution, effects in the hydraulic head difference between the two reservoirs, etc.) or hydrochemical nature (dissolution and/or precipitation of minerals in the aquifer and in the reservoirs, corrosion of facilities, modification of pH, etc.). At this stage, it is required a sound understanding of all the impacts produced by the water exchanges and evaluate under which circumstances they are mitigated. This assessment will allow ascertaining criteria for the selection of the best places to construct future UPSH plants.

How to cite: Pujades, E.: Underground pumped storage hydropower (UPSH) and its interaction with the saturated subsurface medium: effects of the water exchanges on the environment and the plant efficiency, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1127, https://doi.org/10.5194/egusphere-egu21-1127, 2021.

EGU21-348 | Presentations | MAL7 | ERE Division Outstanding ECS Award Lecture 2021

Deformations and permeability variations in fine sediments induced by freezing-thawing cycles caused by borehole heat exchangers

Giorgia Dalla Santa, Simonetta Cola, and Antonio Galgaro

In closed-loop Ground Source Heat Pump system, the circulation of a heat-carrier fluid into the heat exchanger provides the thermal exchange with the underground.

In order to improve the heat extraction from the ground, the fluid temperature is often lowered down to subzero temperatures; as a consequence, the thermal alteration induced in the ground is more intense and can cause freezing processes in the surroundings. In sediments with significant clay fraction, the inner structure and the pore size distribution are irreversibly altered by freezing-thawing cycles.

A wide laboratory program has been performed in order to measure the induced deformations and the permeability variations under different conditions of mechanical loads/depth [1], interstitial water salinity [2] and soil plasticity [3]. In addition, vertical deformations and permeability variations induced by freeze-thaw cycles have been measured also in Over-Consolidated silty clays at different OCR [4].

The results suggest that, despite the induced frozen condition is quite confined close to the borehole [5], in Normal-Consolidated silty clay layers the freezing-thawing-cycles induce an irreversible settlement up to 16%, gathered cycle-after cycle depending on sediment plasticity, pore fluid salinity and applied load. In addition, despite the overall contraction of the soil, the vertical hydraulic conductivity may increase by about 8 times due to a remarkable modification of the soil fabric with increases in pore size, pores connectivity and orientation [6].

The OC silty-clays show an opposite behavior. Experimental results point out that, in case of OC deposits, higher the OCR lower the freeze-thaw induced settlement. In case of OCR > 15, the settlement turns to a slight expansion. Conversely, the observed augment in vertical permeability increases with the OCR degree [4].

These occurrences are significant and irreversible and could affect the functionality of the system as well as lead to environmental effects such as local settlements, negative friction on the borehole heat exchangers or interconnection among aquifers in the probe surroundings.

  • [1]. Dalla Santa G*, Galgaro A, Tateo F, Cola S (2016). Modified compressibility of cohesive sediments induced by thermal anomalies due to a borehole heat exchanger. Engineering Geology 202, 143-152.
  • [2]. Dalla Santa G*, Galgaro A, Tateo F, Cola S (2016). Induced thermal compaction in cohesive sediments around a borehole heat exchanger: laboratory tests on the effect of pore water salinity. Environmental Earth Sciences, 75(3), 1-11.
  • [3]. Cola S, Dalla Santa G, Galgaro A (2020). Geotechnical hazards caused by freezing-thawing processes induced by borehole heat exchangers. Lecture Notes in Civil Engineering, 40, pp. 529–536
  • [4]. Dalla Santa G, Cola S, Galgaro A (2021). Deformation and Vertical Permeability Variations Induced by Freeze-Thaw Cycles in Over-Consolidated Silty Clays. Challenges and Innovations in Geomechanics, 117
  • [5]. Dalla Santa G*, Farina Z, Anbergen H, Rühaak W, Galgaro A (2019). A Comparative Study on the Relevance of Computing Freeze-Thaw Effects for Borehole Heat Exchanger Modelling. Geothermics 79, 164-175.
  • [6]. Dalla Santa G*, Cola S, Secco M, Tateo F, Sassi R, Galgaro A (2019). Multiscale analysis of freeze-thaw effects induced by ground heat exchangers on permeability of silty-clays. Geotechnique 2019, 69(2).

How to cite: Dalla Santa, G., Cola, S., and Galgaro, A.: Deformations and permeability variations in fine sediments induced by freezing-thawing cycles caused by borehole heat exchangers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-348, https://doi.org/10.5194/egusphere-egu21-348, 2021.

MAL8 – ESSI 2020 Ian McHarg Medal Lecture & 2021 Division Outstanding ECS Award Lecture

EGU21-612 | Presentations | MAL8 | Ian McHarg Medal Lecture 2020

The Generic Mapping Tools and Community-Maintained Open Source Software

Paul Wessel

The Generic Mapping Tools (GMT; www.generic-mapping-tools.org) is a well-known set of software for the geosciences, in particular in the marine and solid earth disciplines. GMT is also a prerequisite for many other well-known software infrastructures, including USGS’s ShakeMap for near-real-time maps of ground motion and shaking intensity following significant earthquakes, MBARI/LDEO’s MB-System for multibeam processing and mapping of the seafloor, and Scripps Institution of Oceanography’s GMTSAR for radar interferometric analysis and imaging of crustal deformation. Today, GMT has tens of thousands of users all over the world and remains essential for many terrestrial and planetary data processing and map-making workflows. GMT began its life over 30 years ago when I was a graduate student, and it has enjoyed continuous US National Science Foundation funding since 1993. Leveraging this funding, GMT has succeeded in establishing itself as a collaborative Open Source community resource from the start. Many scientists globally, particularly European scientists, have been instrumental in designing, maintaining, and improving GMT since the early 2000s. As I and several of our core developers approach the end of our academic careers, the GMT team has been pondering how to preserve these collective investments and position GMT to remain an essential geoinformatics infrastructure well into the future. In response, we have made fundamental changes to how GMT works, enabling access to GMT modules from external interfaces such as MATLAB/Octave, Python, and Julia, simplifying user access to large global datasets, and extending our support for the Google Earth platform. However, the biggest impact delivered by the Fall 2019 release of GMT 6 is likely “modern mode”. Modern mode coexists with classic mode (the only previous mode) so that thousands of GMT 4 and 5 scripts will still run as expected. Furthermore, new users will start with modern mode and experience a much-simplified GMT scripting syntax. A new aspect of GMT made possible by modern mode is a greatly simplified animation production. It is clear to all scientists that animations make it easier to elucidate temporal or spatial changes, yet very few scientists create animations as they are traditionally the domain of experts. The GMT team aspires to make animations a task every scientist can do with ease. In this lecture, I will discuss the latest news on GMT, outline modern mode and the external environment access to our modules, highlight a few GMT animations, and present other aspects of our succession planning for strengthening the GMT community.

How to cite: Wessel, P.: The Generic Mapping Tools and Community-Maintained Open Source Software, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-612, https://doi.org/10.5194/egusphere-egu21-612, 2021.

EGU21-4055 | Presentations | MAL8 | ESSI Division Outstanding ECS Award Lecture 2021

Supporting open data: the key role of data managers

Alice Fremand

Open data is not a new concept. Over sixty years ago in 1959, knowledge sharing was at the heart of the Antarctic Treaty which included in article III 1c the statement: “scientific observations and results from Antarctica shall be exchanged and made freely available”. ​At a similar time, the World Data Centre (WDC) system was created to manage and distribute the data collected from the International Geophysical Year (1957-1958) led by the International Council of Science (ICSU) building the foundations of today’s research data management practices.

What about now? The WDC system still exists through the World Data System (WDS). Open data has been endorsed by a majority of funders and stakeholders. Technology has dramatically evolved. And the profession of data manager/curator has emerged. Utilising their professional expertise means that their role is far wider than the long-term curation and publication of data sets.

Data managers are involved in all stages of the data life cycle: from data management planning, data accessioning to data publication and re-use. They implement open data policies; help write data management plans and provide advice on how to manage data during, and beyond the life of, a science project. In liaison with software developers as well as scientists, they are developing new strategies to publish data either via data catalogues, via more sophisticated map-based viewer services or in machine-readable form via APIs. Often, they bring the expertise of the field they are working in to better assist scientists satisfy Findable, Accessible, Interoperable and Re-usable (FAIR) principles. Recent years have seen the development of a large community of experts that are essential to share, discuss and set new standards and procedures. The data are published to be re-used, and data managers are key to promoting high-quality datasets and participation in large data compilations.

To date, there is no magical formula for FAIR data. The Research Data Alliance is a great platform allowing data managers and researchers to work together, develop and adopt infrastructure that promotes data-sharing and data-driven research. However, the challenge to properly describe each data set remains. Today, scientists are expecting more and more from their data publication or data requests: they want interactive maps, they want more complex data systems, they want to query data, combine data from different sources and publish them rapidly.  By developing new procedures and standards, and looking at new technologies, data managers help set the foundations to data science.

How to cite: Fremand, A.: Supporting open data: the key role of data managers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4055, https://doi.org/10.5194/egusphere-egu21-4055, 2021.

MAL9 – G 2020/2021 Vening Meinesz Medal Lectures

EGU21-409 | Presentations | MAL9 | Vening Meinesz Medal Lecture 2020

Decorrelative Mollifier Gravimetry

Willi Freeden

The lecture highlights arguments that, coming from multiscale mathematics, have fostered the advancement of gravimetry, as well as those that, generated by gravimetric problems, have contributed to the enhancement in constructive approximation and numerics. Inverse problems in gravimetry are delt with multiscale mollifier decorrelation strategies. Two examples are studied in more detail: (i) Vening Meinesz multiscale surface mollifier regularization to determine locally the Earth's disturbing potential from deflections of vertical, (ii) Newton multiscale volume mollifier regularization of the inverse gravimetry problem to derive locally the density contrast distribution from functionals of the Newton integral and to detect fine particulars of geological relevance. All in all, the Vening Meinesz medal  lecture is meant as an  \lq \lq appetizer'' served to enjoy the tasty meal "Mathematical Geoscience Today'' to be shared by geoscientists and mathematicians in the field of gravimetry. It provides innovative concepts and locally relevant applications presented in a monograph to be published by Birkhäuser in the book series “Geosystems Mathematics” (2021).

How to cite: Freeden, W.: Decorrelative Mollifier Gravimetry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-409, https://doi.org/10.5194/egusphere-egu21-409, 2021.

EGU21-596 | Presentations | MAL9 | Vening Meinesz Medal Lecture 2021

The Deflection of the Vertical, from Bouguer to Vening-Meinesz, and Beyond – the unsung hero of geodesy and geophysics

Christopher Jekeli

When thinking of gravity in geodesy and geophysics, one usually thinks of its magnitude, often referred to a reference field, the normal gravity.  It is, after all, the free-air gravity anomaly that plays the significant role in terrestrial data bases that lead to Earth Gravitational Models (such as EGM96 or EGM2008) for a multitude of geodetic and geophysical applications.  It is the Bouguer anomaly that geologists and exploration geophysicists use to infer deep crustal density anomalies.  Yet, it was also Pierre Bouguer (1698-1758) who, using the measured direction of gravity, was the first to endeavor a determination of Earth’s mean density (to “weigh the Earth”), that is, by observing the deflection of the vertical due to Mount Chimborazo in Ecuador.  Bouguer’s results, moreover, sowed initial seeds for the theories of isostasy.  With these auspicious beginnings, the deflection of the vertical has been an important, if not illustrious, player in geodetic history that continues to the present day.  Neglecting the vertical deflection in fundamental surveying campaigns in the mid to late 18th century (e.g., Lacaille in South Africa and Méchain and Delambre in France) led to errors in the perceived shape of the Earth, as well as its scale that influenced the definition of the length of a meter.  The vertical deflection, though generally excluded from modern EGM developments, nevertheless forms a valuable resource to validate such models.  It is also the vertical deflection that is indispensable for precision autonomous navigation (i.e., without external aids such as GPS) using inertial measurement units.  It is the deflection of the vertical that, measured solely along horizontal lines, would readily provide geoid undulation profiles, essential for the modernization of height systems (i.e., vertical geodetic control) without the laborious and traditional methods of spirit leveling.  But, measuring the deflection of the vertical is itself an arduous undertaking and this has essentially contributed to its neglect and/or underusage.  Even Vening-Meinesz’s formulas of convolution with gravity anomalies do not greatly facilitate its determination.  This presentation offers a review of the many roles the vertical deflection has, or could have, played over the centuries, how it has been measured or computed, and how gravity gradiometry might eventually awaken its full potential.

How to cite: Jekeli, C.: The Deflection of the Vertical, from Bouguer to Vening-Meinesz, and Beyond – the unsung hero of geodesy and geophysics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-596, https://doi.org/10.5194/egusphere-egu21-596, 2021.

MAL10 – GD 2020/2021 Augustus Love Medal Lectures & Division Outstanding ECS Award Lectures

EGU21-5339 | Presentations | MAL10 | GD Divison Outstanding ECS Award Lecture 2020

Numerical modelling of igneous processes

Tobias Keller

Magma matters. From magmatic differentiation of terrestrial planets into core, mantle and crust, to magmatism modulating plate tectonics and deep volatile cycles that maintain a habitable Earth, and volcanism causing terrible hazards but also providing rich energy and mineral resources – igneous processes are integral to the evolution of Earth and other terrestrial planetary bodies. Our understanding of volcanoes and their deep magmatic roots derives from a range of disciplines including field geology, experimental petrology, geochemical analyses, geophysical imaging, and volcano monitoring. Observational and experimental studies, however, are hampered by incomplete access to processes that play out across scales ranging from sub-millimetre size to thousands of kilometres, and from seconds to billions of years. Computational modelling provides a tool kit for investigating igneous processes across these scales.

Over the past decade, my research has been focused on advancing the theoretical description and numerical application of multi-phase reaction-transport processes at the volcano to planetary scale. Mixture theory provides a framework to represent the spatially averaged behaviour of a large sample of microscopic phase constituents including mineral grains, melt films, fluid droplets, and vapour bubbles. The approach has been used successfully to model both porous flow of melt percolating through compacting rock, as well as suspension flow of crystals settling in convecting magma bodies. My recent work has introduced a new modelling framework that bridges the porous to mushy and suspension flow limits, and extends beyond solid-liquid systems to multi-phase systems including several solid, liquid, and vapour phases. Igneous process modelling can thus provide new insights into the generation and extraction of mantle melts, the dynamics of crustal magma processing, the outgassing and eruption of shallow magma reservoirs, and the generation of mineral resources by exsolution of enriched magmatic liquids.

How to cite: Keller, T.: Numerical modelling of igneous processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5339, https://doi.org/10.5194/egusphere-egu21-5339, 2021.

Introduction

At various regions within the dynamic earth melts are generated due to decompressional melting, reduction of the solidus temperature due to volatiles or due to elevated temperatures. They segregate from these partially molten regions, rise by various transport mechanisms and may form crustal magmatic systems where they are emplaced or erupt. The physics of various aspects of this magmatic cycle will be addressed.

Melt transport mechanisms

Starting from a partially molten region by which mechanism(s) does the melt segregate out of the melt source region and rise through the mantle or crust? The basic mechanism is two-phase flow, i.e. a liquid phase percolates through a solid, viscously deforming matrix. The corresponding equations and related issues such as compaction or effective matrix rheology are addressed. Beside simple Darcy flow, special solutions of the equations are addressed such as solitary porosity waves. Depending on the bulk to shear viscosity ratio of the matrix and the non-dimensional size of these waves, they show a variety of features: they may transport melt over large distances, or they show transitions from rising porosity waves to diapiric rise or to fingering. Other solutions of the equations lead to channeling, either mechanically or chemically driven. One open question is how do such channels transform into dykes which have the potential of rising through sub-solidus overburden. A recent hypothesis addresses the possibility that rapid melt percolation may reach the thermal non-equilibrium regime, i.e. the local temperature of matrix and melt may evolve differently.  Once dykes have been formed they may propagate upwards driven by melt buoyancy and controlled by the ambient stress field. Often in dynamic models the complexities of melt transport are simplified by parameterized melt extraction. The limitations of such simplifications will be addressed.

Modelling magmatic systems in thickened continental crust

Once basaltic melts rise from the mantle, they may underplate continental crust and generate silicic melts. Early dynamic models (Bittner and Schmeling, 1995, Geophys. J. Int.) showed that such silicic magma bodies may rise to mid-crustal depth by diapirism. More recent approaches (e.g. Blundy and Annan, 2016, Elements) emplace sill intrusions into the crust at various levels and calculate the thermal and melting effects responsible for the formation of mush zones. Recently Schmeling et al. (2019, Geophys. J. Int.) self-consistently modelled the formation of crustal magmatic systems, mush zones and magma bodies by including two-phase flow, melting/solidification and effective power-law rheology. In these models melt is found to rise to mid-crustal depths by a combination of compaction/decompaction assisted two-phase flow, sometimes including solitary porosity waves, diapirism or fingering. An open question in these models is whether or how dykes may self-consistently form to transport the melts to shallower depth. First models which combine elastic dyke-propagation (Maccaferri et al., 2019, G-cubed) with the two-phase flow crustal models are promising.

How to cite: Schmeling, H.: Melting and melt transport mechanisms in the dynamic earth: from melt segregation, extraction to the formation of crustal magmatic systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4971, https://doi.org/10.5194/egusphere-egu21-4971, 2021.

EGU21-13877 | Presentations | MAL10 | GD Divison Outstanding ECS Award Lecture 2021

Exploring links between geodynamics and climate change

Mark Hoggard and Fred Richards

Combating global climate change remains one of the greatest challenges facing humanity in the coming decades. Whilst oceanographers, ice sheet dynamicists, and atmospheric modellers all have an obvious role to play in leading efforts to tackle this problem, there remain many aspects that require careful consideration and cross-disciplinary interaction in other areas of the geosciences. In this talk, I will use selected examples to illustrate important links between geodynamics and climate change, including improving our understanding of its potential impacts and mitigation. The first concerns the role of mantle convection in influencing palaeo sea-level records and ice sheet dynamics. For example, Pliocene interglacial periods are commonly invoked as potential climatic analogues for the near-future conditions expected in our warming world, but there is considerable uncertainty over the extent to which important sea-level indicator sites have been perturbed, post-deposition, by convection-induced dynamic topography. The second link involves the growing shortage of metals that are key to the manufacture of technologies for low-carbon energy generation and storage. Tackling this shortfall requires an improvement in our ability to locate new, high-grade metal deposits, particularly those buried beneath shallow sedimentary cover. Novel geodynamical insights into the geological processes responsible for ore genesis will form a core component of narrowing the exploration search-space, and we have recently demonstrated this approach for sediment-hosted metal deposits. Through these case studies, I will show that it is primarily through developing an environment of cross-disciplinary discussion and financial support that our community is most likely to progress in understanding the potential impacts of climate change and how we may mitigate against them. Although one of the least well-studied components, the solid Earth is increasingly being recognised as a critical part of the climate system. Researchers working in topics as diverse as rock mechanics, seismology, convection modelling, and geochemistry all have a crucial role to play.

How to cite: Hoggard, M. and Richards, F.: Exploring links between geodynamics and climate change, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13877, https://doi.org/10.5194/egusphere-egu21-13877, 2021.

EGU21-9245 | Presentations | MAL10 | Augustus Love Medal Lecture 2021

Heterogeneous lithospheric mantle

Irina M. Artemieva

The lithosphere is a thermal boundary layer atop mantle convection and a chemical boundary layer formed by mantle differentiation and melt extraction. The two boundary layers may everywhere have different thicknesses. Worldwide, the thicknesses of thermal and chemical boundary layers vary significantly, reflecting thermal and compositional heterogeneity of the lithospheric mantle.

Physical parameters determined by remote geophysical sensing (e.g. seismic velocities, density, electrical conductivity) are sensitive to both thermal and compositional heterogeneity. Thermal anomalies are usually thought to have stronger effect than compositional anomalies, especially at near-solidus temperatures when partial melting and anelastic effects become important. Therefore, geophysical studies of mantle compositional heterogeneity require independent constraints on the lithosphere thermal regime. The latter can be assessed by various methods, and I will present examples for continental lithosphere globally and regionally. Of particular interest is the thermal heterogeneity of the lithosphere in Greenland, with implications for the fate of the ice sheet and possible signature of Iceland hotspot track.

Compositional heterogeneity of lithospheric mantle at small scale is known from Nature's sampling, such as by mantle-derived xenoliths brought to the surface of stable Precambrian cratons by kimberlite-type magmatism. This situation is paradoxical since “stable” regions are not expected to be subject to any tectono-magmatic events at all. Kimberlite magmatism should lead to a significant thermo-chemical modification of the cratonic lithosphere, which otherwise is expected to have a unique thickness (>200 km) and unique composition (dry and depleted in basaltic components). Nevertheless, geochemical studies of mantle xenoliths provide the basis for many geophysical interpretations at large scale.

Magmatism-related thermo-chemical processes are reflected in the thermal, density, and seismic velocity structure of the cratonic lithosphere. Based on joint interpretation of geophysical data, I demonstrate the presence of significant lateral and vertical heterogeneity in the cratonic lithospheric mantle worldwide. This heterogeneity reflects the extent of lithosphere reworking by both regional-scale kimberlite-type magmatism (e.g. Kaapvaal, Siberia, Baltic and Canadian Shields) and large-scale tectono-magmatic processes, e.g. associated with LIPs and subduction systems such as in the Siberian and North China cratons. The results indicate that lithosphere chemical modification is caused primarily by mantle metasomatism where the upper extent may represent a mid-lithosphere discontinuity. An important conclusion is that the Nature’s sampling by kimberlite-hosted xenoliths is biased and therefore is non-representative of pristine cratonic mantle.

I also present examples for lithosphere thermo-chemical heterogeneity in tectonically young regions, with highlights from Antarctica, Iceland, North Atlantics, and the Arctic shelf. Joint interpretation of various geophysical data indicates that West Antarctica is not continental, as conventionally accepted, but represents a system of back-arc basins. In Europe and Siberia, an extremely high-density lithospheric mantle beneath deep sedimentary basins suggests the presence of eclogites in the mantle, which provide a mechanism for basin subsidence. In the North Atlantic Ocean, thermo-chemical heterogeneity of the upper mantle is interpreted by the presence of continental fragments, and the results of gravity modeling allow us to conclude that any mantle thermal anomaly around the Iceland hotspot, if it exists, is too weak to be reliably resolved by seismic methods.

https://stanford.academia.edu/IrinaArtemieva

www.lithosphere.info

How to cite: Artemieva, I. M.: Heterogeneous lithospheric mantle, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9245, https://doi.org/10.5194/egusphere-egu21-9245, 2021.

MAL11 – GI 2020/2021 Christiaan Huygens Medal Lectures & 2021 Division Outstanding ECS Award Lecture

EGU21-16499 | Presentations | MAL11 | Christiaan Huygens Medal Lecture 2020

Multi-length probes in GPR and TDR data

Raffaele Persico

I will expose some possibilities regarding the use of metallic probes of different lengths in GPR and TDR prospecting. With regard to GPR, multi-length probes are dipole-like antennas whose length can be changed by means of switches. The switches can be implemented with PIN diodes, and can act as electronic “knifes”. Therefore, they allow to cut (switched off) or prolong (switched on) the branches of a couple of antennas, and this allows to have more couples of equivalent antennas making use of a unique physical couple of antennas. This allows to contain the size of the system. In particular, a reconfigurable prototypal stepped frequency GPR system was developed within the project AITECH (http://www.aitechnet.com/ibam.html) and was tested in several cases histories  [1-3]. Within this reconfigurable GPR, it is also possible to reconfigure vs. the frequency the integration times of the harmonic tones constituting the radiated signal. This feature allows to reject external electromagnetic interferences without filtering the spectrum of the received signal [4] and without increasing the radiated power.

With regard to TDR measurements, a multi-length probe consists of a TDR device where the rods (in multi-wire version) or the length of internal and external conductor (in coaxial version) can be changed. This can be useful for the measurements of electromagnetic characteristics of a material under test (MUT), in particular its dielectric permittivity and magnetic permeability, both meant in general as complex quantities. Multi-length TDR measurements allow to acquire independent information on the MUT even at single frequency, and this can be of interest in the case of dispersive materials [5-6].

Acknowledgements

I collaborated with several colleagues about the above issues. To list of them would be long, so I will just mention their affiliations: Florence Engineering srl, University of Florence, IDSGeoradar srl, 3d-radar Ltd, Institute for Archaeological and Monumental Heritage IBAM-CNR, University of Bari, University of Malta. Finally, a particular mention is deserved for the Cost Action TU1208.

References

[1] R. Persico, M. Ciminale, L. Matera, A new reconfigurable stepped frequency GPR system, possibilities and issues; applications to two different Cultural Heritage Resources, Near Surface Geophysics, 12, 793-801, 2014.

[2] L. Matera, M. Noviello, M. Ciminale, R. Persico, Integration of multisensor data: an experiment in the archaeological park of Egnazia (Apulia, Southern Italy), Near Surface Geophysics, 13, 613-621, 2015.

[3] R. Persico, S. D'Amico, L. Matera, E. Colica, C. De, Giorgio, A. Alescio, C. Sammut and P. Galea, P. (2019), GPR Investigations at St John's Co‐Cathedral in Valletta, Near Surface Geophysics, 17, 213-229, 2019.

[4] R. Persico, D. Dei, F. Parrini, L. Matera, Mitigation of narrow band interferences by means of a reconfigurable stepped frequency GPR system, Radio Science, 51, 2016.

[5] R. Persico, M. Pieraccini, Measurement of dielectric and magnetic properties of Materials by means of a TDR probe, Near Surface Geophysics, 16,1-9, 2018.

[6] R. Persico, I. Farhat, L. Farrugia, S. d’Amico, C. Sammut, An innovative use of TDR probes: First numerical validations with a coaxial cable, Journal of Environmental & Engineering Geophysics, 23, 437-442, 2018.

 

How to cite: Persico, R.: Multi-length probes in GPR and TDR data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16499, https://doi.org/10.5194/egusphere-egu21-16499, 2021.

EGU21-8364 | Presentations | MAL11 | Christiaan Huygens Medal Lecture 2021

“Perspicacity… and a degree of good fortune”: opportunities for revealing the natural world

R.Giles Harrison

Experimental science is now more possible and accessible than ever, due to the ready abundance of sensors and recording systems. However, as commercial development of sensors generally follows demand and profitability, most of the options are restricted to devices sensing the most commonly monitored physical quantities. A scientific need can therefore still arise - which Christiaan Huygens would no doubt recognise, and indeed confronted so ably - for an entirely new instrument. As for Huygens’ era, the role of the experimentalist includes seeking and exploiting the best method available for each scientific investigation. This includes modern advances in electronics, materials and production. I will describe some of my own work in atmospheric electricity to try to illustrate the continued value of this approach, in which scientific objectives have driven the design, development and deployment of new instruments for which there were no commercial options. Existing measurement infrastructures, for example surface meteorological observing systems and weather balloon networks, can be enhanced as a result, from embedding and including new sensors, instruments and devices.

How to cite: Harrison, R. G.: “Perspicacity… and a degree of good fortune”: opportunities for revealing the natural world, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8364, https://doi.org/10.5194/egusphere-egu21-8364, 2021.

EGU21-1482 | Presentations | MAL11 | GI Division Outstanding ECS Award Lecture 2021

GeoAI:artificial intelligence for interpretation and processing of complex geomatic data 

Roberto Pierdicca

Nowadays, the exploitation artificial intelligence approached is overwhelming in several domains. As well, geomatic data are becoming more and more complex and heterogeneous, as they are collected with multi-source data collection techniques. Remotely sensed data, point cloud, thermal images and more are just few examples of complex data which requires growing computational capabilities, but, foremost, powerful tools of processing and interpretation.

The applications of modern AI-based algorithms for the processing of geomatics data offer opportunities that wouldn't be affordable up to few years ago. For geospatial domains, fundamental questions include how AI can be specifically applied to or has to be specifically created for geomatics data. This change is also having a significant impact on geospatial data. Machine Learning (ML) has been a core component of spatial analysis for classification, clustering, and prediction. In addition, Deep Learning (DL) is being integrated to automatically extract useful information with the task of classification, object detection, semantic and instance segmentation, etc. The integration of AI, ML, and DL in geomatics has developed into the concept of Geospatial Artificial Intelligence (GeoAI) that is a new paradigm for geographic knowledge discovery and beyond. 

This talk aims at giving a sight on the emergent discipline called GeoAI, a novel research field in which cutting edge learning based methods are applied to enhance the knowledge and improve the ability of humans to manage complex information. Beside providing a picture of the latest achievements in the filed (outlining AI-based techniques for the analysis and the interpretation of complex geomatics data), this lecture will provide several examples of researches and applications, demonstrating opportunities, challenges and limitations with practical examples. 

Bearing in mind that, for the upcoming future, the "man on the loop" will always assess unpredictable outcomes from the automatization process, it will be demonstrated, at different scales of representation and facing research challenges in different domains (e.g. environmental challenges, forestry, cultural heritage, tourism just to mention some), AI outperforms manual operations in terms of both cost effectiveness and reliability. 

How to cite: Pierdicca, R.: GeoAI:artificial intelligence for interpretation and processing of complex geomatic data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1482, https://doi.org/10.5194/egusphere-egu21-1482, 2021.

MAL12 – GM 2020/2021 Ralph Alger Bagnold Medal Lectures

EGU21-16452 | Presentations | MAL12 | Ralph Alger Bagnold Medal Lecture 2020

Geomorphic Apophenia: Inferring meaning where there could be none?

Tom Coulthard

Apophenia describes the experience of seeing meaningful patterns or connections in random or meaningless data. Francis Bacon was one of the first to identify its role as a "human understanding is of its own nature prone to suppose the existence of more order and regularity in the world than it finds". Since then, experiments using streams of randomly generated binary sequences show a propensity for people to believe random data fluctuates more than it actually does. A more mainstream example of this is gamblers fallacy, where lucky or unlucky streaks are identified in the random selection of a roulette wheel. Furthermore, humans can also be influenced by a pre-existing ideas or a narrative that they then transpose into their findings leading to tending to support a hypothesis instead of disproving (confirmation bias).  

As much of geomorphological science involves the interpretation of data, we argue that the persuasiveness of a narrative and human difficulties in recognizing genuinely random data could lead to apophenia. This presentation examines where apophenia might affect geomorphology, using examples from sediment stratigraphy, signal shredding, river meandering and the numerical modelling of landscape systems. In particular, we focus on how seductive it can be to link changes in landscape to drivers when there are potentially hazardous gaps in the data we are using.

In Geomorphology correlation has for long been substituted by causation. However, with emerging data rich methods including structure from motion, seismology, remote sensing and numerical modelling, former ‘classic’ techniques of qualitative interpretation can give way to quantitative hypothesis testing.

How to cite: Coulthard, T.: Geomorphic Apophenia: Inferring meaning where there could be none?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16452, https://doi.org/10.5194/egusphere-egu21-16452, 2021.

EGU21-11854 | Presentations | MAL12 | Ralph Alger Bagnold Medal Lecture 2021

High Latitude Dust: contemporary emissions and geomorphic interactions

Joanna Bullard

The world’s largest contemporary dust sources are in low-lying, hot, arid regions, however the processes of dust production and emission also operate in cold climate regions at high latitudes and altitudes.  This lecture focuses on contemporary dust emissions originating from the high latitudes (≥50°N and ≥40°S) and explores three themes before setting out an integrated agenda for future research.  The first theme considers how much dust originates from the high latitudes and methods for determining this.  Estimates from field studies, remote sensing and modelling all suggest around 5% of contemporary global dust emissions originate in the high latitudes, a similar proportion to that from the USA (excluding Alaska) or Australia.  This estimate is a proportion of a highly uncertain figure as quantification of dust emissions from Eurasian high latitudes is limited, and the contribution of local and regional emissions (from any latitude) to the global total is thought to be considerably under-estimated.  Emissions are particularly likely to be under-estimated where dust sources are topographically constrained, and where cold climates reduce vertical mixing of dust plumes restricting the altitudes to which the dust can rise, because both these characteristics present particular challenges for modelling and remote sensing approaches. The second theme considers the drivers of contemporary high latitude dust emissions that reflect complex interactions among sediment supply, sediment availability and transport capacity across different geomorphic sub-systems.  These interactions determine the magnitude, frequency and timing of dust emissions at a range of time scales (diurnal, seasonal, decadal) but both the drivers and response can be nonlinear and hard to predict.  The third and final theme explores the importance of high latitude dust cycling for facilitating cross-boundary material fluxes and its impact in the atmosphere, cryosphere, and terrestrial and marine ecosystems.  This is influenced not only by the quantity and timing of dust emissions but also by dust properties such as particle-size and geochemistry.  Landscape sensitivity, spatial environmental transitions and temporal environmental change are highlighted for their importance in determining how the interactions among drivers and cycles are likely to change in response to future environmental change.

How to cite: Bullard, J.: High Latitude Dust: contemporary emissions and geomorphic interactions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11854, https://doi.org/10.5194/egusphere-egu21-11854, 2021.

MAL13 – GMPV 2020/2021 Robert Wilhelm Bunsen Medal Lectures & 2021 Division Outstanding ECS Award Lecture

EGU21-13563 | Presentations | MAL13 | Robert Wilhelm Bunsen Medal Lecture 2020

How Two Unassuming Elements, Re and Os, Assumed Acclaim in the Geosciences

Holly Stein

Re and Os (rhenium and osmium) are chalcophile-siderophile elements (transition metals) with a unique position in isotope geochemistry.  Unlike other commonly used decay schemes for radiometric dating, these metals take residency in resource-related media, for example, sulfide minerals, the organic component in black shales, coals, and bitumens and oils.  In sum, the reducing environment is their haven whereas under oxidizing conditions, Re and Os become unmoored and the radiometric clock becomes compromised.  The clock is not temperature sensitive, and its applicability spans Early Archean to Pleistocene. 

This Bunsen Medal lecture will explore and review the challenges in bringing Re-Os from the meteorite-mantle community into the crustal environment.  At the center of it all is our ability to turn geologic observation into a thoughtful sampling strategy.  The potential to date ore deposits was an obvious application and molybdenite [Mo(Re)S2], rarely with significant common Os and rarely with overgrowths, became an overnight superstar, yielding highly precise, accurate, and reproducible ages.  Yet, molybdenite presented our first sampling challenge with recognition of a puzzling parent-daughter (187Re-187Os) decoupling in certain occurrences.  A strategic sampling procedure was employed.  From there, the diversity of applications spread, as molybdenite is also an accessory mineral in many granitoids, and can be a common trace sulfide in metamorphic rocks.  Whether conformable with and/or crosscutting foliation, molybdenite ages define the timing of deformational events.  Pyrite and arsenopyrite can also be readily dated. 

Applications jumped from sulfides to organic matter.  The hydrogenous component from organic matter in black shales gives us Re-Os ages in the sedimentary record for the Geologic Time Scale.  This led to construction of an Os isotope seawater curve – an ongoing process.  Unlike the well-known Sr seawater curve, the short residence time of Os in the oceans creates a high-definition time record with unambiguous high-amplitude swings in 187Os/188Os.  Re-Os puts time pins into the biostratigraphic record, and we have even directly dated fossils.  Re-Os opened the door for a new generation of paleoclimate studies to evaluate seawater conditions at the time of organic blooms and organic sequestration in bottom mud.  Uplift and continental erosion can be balanced with hydrothermal input into oceans based on changes in the Os isotope composition of seawater.  The timing and connectivity of opening seaways can be determined, and the timing of glaciation and deglaciation events can be globally correlated.  The timing and instigators of mass extinctions are carried in the Re-Os record.  A major meteorite impact places an enormous scar in the Os isotope record as seawater drops toward mantle values but recovers in just a few thousand years.  Most recently, Re-Os has transformed our understanding of the events and fluids involved in construction of whole petroleum systems. 

Looking to the future, what kinds of data sets will be explored and what are the interdisciplinary skill sets needed to interpret those data?  Re-Os will continue to provide us with new ways to dismantle geologic media for new scientific understanding of processes that have shaped our lithosphere, biosphere and hydrosphere, recording their intersection and exchange. 

How to cite: Stein, H.: How Two Unassuming Elements, Re and Os, Assumed Acclaim in the Geosciences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13563, https://doi.org/10.5194/egusphere-egu21-13563, 2021.

EGU21-1602 | Presentations | MAL13 | GMPV Division Outstanding ECS Award Lecture 2021

Hydrogen diffusion in olivine: challenges and opportunities

Michael Jollands

Understanding rates and mechanisms of diffusion in geologically relevant materials is important when considering, for example, electrical conductivity, rheology and, of course, diffusion chronometry. Olivine has received much attention in this regard – not only is it important in upper mantle and many volcanic settings, but its wide range of stability in pressure-temperature-chemical activity space makes it extremely amenable to experimental petrology. Furthermore, olivine is simple enough to study systematically, but contains different crystallographic sites, diffusion pathways and is anisotropic, thus has sufficient complexity to remain interesting. Like many common rock-forming minerals, olivine is nominally anhydrous, but normally contains trace amounts of hydrogen. This is generally bonded to structural oxygen, forming hydroxyl groups. These can be easily imaged by infrared spectroscopy, which simultaneously elucidates both their concentration and associated point defect chemistry.

The combination of a mineral that is quite straightforward to study experimentally, and the ability to distinguish between different H substitution mechanisms, a major strength of infrared spectroscopy, has proved to be hugely useful. However, the more we know, the more complex the system seems to become. For example, firstly, small changes in the major element composition of olivine were shown to have considerable effects on H diffusion. Secondly, close inspection of infrared spectra from experiments and natural samples revealed the presence of point defects that, according to the generally invoked theory, should not be there. Thirdly, small variations in experimental design between different studies apparently led to major discrepancies in results, even if the experiments were designed to measure ostensibly the same process. Fourthly, apparent diffusivities extracted from well-constrained natural samples showed results in complete disagreement with experiments in the same system.

On the one hand, these complexities have the potential to severely limit the accuracy of diffusion chronometry using H diffusion. On the other hand, complexity is opportunity. Given the wealth of published studies, both experimental and natural, and given that H-bearing point defects in olivine can be easily distinguished, we are presented with a unique possibility to truly unravel the diffusive behaviour of H in olivine. Recently developed theories suggest that treating H mobility as diffusion alone is insufficient (even if multiple diffusion mechanisms are invoked), and instead it is necessary to consider the way in which different H-bearing point defects interact within the crystal. A model describing this process in both pure and trace element-doped forsterite will be presented, which reconciles, to some extent, these previous discrepancies. The model suggests that the true mobility of H is one to two orders of magnitude higher than that which has been directly measured when assuming simple diffusion. Work is in progress to expand the model towards crystals with chemistries relevant for nature. If a similar model can be invoked for natural olivine, then this will require that models of processes invoking H diffusion (e.g. rheology, diffusion chronometry, electrical conductivity) will need to be reevaluated.

How to cite: Jollands, M.: Hydrogen diffusion in olivine: challenges and opportunities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1602, https://doi.org/10.5194/egusphere-egu21-1602, 2021.

EGU21-896 | Presentations | MAL13 | Robert Wilhelm Bunsen Medal Lecture 2021

Geochronology - a suitable tool to discern causality from temporal coincidence?

Urs Schaltegger

Geoscientists tend to subdivide the system Earth into different subsystems (geosphere, hydrosphere, atmosphere, biosphere), which are interacting with each other in a non-linear way. The quantitative understanding of this interaction is essential to make reconstructions of the geological past. This is mostly done by a linear approach of establishing time-series of chemical and physical proxies, calibrating their contemporaneity through geochronology, and eventually invoke causality. A good example is the comparison of carbon or oxygen isotope time series to the paleo-biodiversity in ancient sedimentary sections, temporally correlated using astrochronology or high-precision U-Pb dating of volcanic zircon in interlayered ash beds. While highly accurate and precise data are necessary to form the basis for linear and non-linear models, we have to be aware that any analysis is the result of an experiment – an isotope-chemical analysis in the U-Pb example - introducing random and non-random noise, which can mimic, disturb, distort or mask non-linear system behavior. High-precision/high-accuracy U-Pb age determination using the mineral zircon (ZrSiO4) and application of the techniques of isotope dilution, thermal ionization mass spectrometry is a good example of such an experiment we apply to the geological history of our planet.

Two examples where precise U-Pb dating methods are used to link disparate processes are (1) using the duration and the tempo of zircon growth in a magmatic system as a measure for modeling magma flux in space and time, and apply these to infer potential eruptibility and volcanic hazard of a plutonic-volcanic plumbing system; (2) establish absolute age and duration of magma emplacement in large igneous provinces, feed these data into models of volatile injection into and residence of volatile species in the atmosphere, estimate their influence on the inherent parameters of Earth’s climate, and infer causality with climatic, environmental and biotic crises. Both of these are outstanding scientific questions that attract and deserve significant attention by a general as well as academic public. However, insufficient attention is drawn onto the questions of the nature and importance of the noise we add through isotopic age determination.

There are two prominent issues to be discussed in this context, (1) to what extent (at what precision) can we distinguish natural age variation among zircon grains from random scatter produced by analytical techniques and the complexity of the U-Pb isotopic system in zircon, and (2) how can we correlate the U-Pb dates established for crystallization of zircon in residual and/or assimilated melt portions of mafic magmatic rocks from large igneous provinces to the release and injection of magmatic and contact-metamorphic volatiles into the atmosphere? This contribution intends to demonstrate that analytical scatter and complex system behavior are often confounded with age variation (and vice versa) and will outline new approaches and insights how to quantify their respective contributions.

How to cite: Schaltegger, U.: Geochronology - a suitable tool to discern causality from temporal coincidence?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-896, https://doi.org/10.5194/egusphere-egu21-896, 2021.

MAL14a – HS 2020/2021 Henry Darcy Medal lectures & 2020 Arne Richter Award for Outstanding ECS Lecture

EGU21-15490 | Presentations | MAL14a | Henry Darcy Medal Lecture 2020

Porous media as a canvas for hydro-bio-geo-chemical processes: Facing the challenges

Xavier Sanchez-Vila

The more we study flow and transport processes in porous media, the larger the number of questions that arise. Heterogeneity, uncertainty, multidisciplinarity, and interdisciplinarity are key words that make our live as researchers miserable… and interesting. There are many ways of facing complexity; this is equivalent as deciding what colors and textures to consider when being placed in front of a fresh canvas, or what are the sounds to include and combine in a music production. You can try to get as much as you can from one discipline, using very sophisticated state-of-the-art models. On the other hand, you can choose to bring to any given problem a number of disciplines, maybe having to sacrifice deepness in exchange of the better good of yet still sophisticated multifaceted solutions. There are quite a number of examples of the latter approach. In this talk, I will present a few of those, eventually concentrating in managed aquifer recharge (MAR) practices. This technology involves water resources from a myriad of perspectives, covering from climate change to legislation, from social awareness to reactive transport, from toxicological issues to biofilm formation, from circular economy to emerging compounds, from research to pure technological developments, and more. All of these elements deserve our attention as researchers, and we cannot pretend to master all of them. Integration, development of large research groups, open science are words that will appear in this talk. So does mathematics, and physics, and geochemistry, and organic chemistry, and biology. In any given hydrogeological problem you might need to combine equations, statistics, experiments, field work, and modeling; expect all of them in this talk. As groundwater complexity keeps amazing and mesmerizing me, do not expect solutions being provided, just anticipate more and more challenging research questions being asked.

How to cite: Sanchez-Vila, X.: Porous media as a canvas for hydro-bio-geo-chemical processes: Facing the challenges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15490, https://doi.org/10.5194/egusphere-egu21-15490, 2021.

EGU21-12778 | Presentations | MAL14a | Henry Darcy Medal Lecture 2021

Landscape perspectives in hydrological understanding and modelling for water management

Berit Arheimer

The Darcy medal acknowledges water-resources research, engineering and management. In my medal lecture I will embrace these aspects by telling the story of how my team merges numerical models and observations with landscape information to learn about hydrological processes and provide decision-support to society. We predict spatial and temporal variability of water fluxes and resources at local, regional and global scales to estimate hydrological variables in the past, present and future. We also explore “what if” scenarios for societal planning. Such predictions provide useful knowledge to maintain water resources at suitable quantities and qualities, despite on-going global warming, urbanization and environmental change. Water is the basis for all life and most societal sectors; hence, it must be managed properly for sustainable development. I will demonstrate how our scientific findings from the model applications have influenced water resources engineering and management policy.

Water management is always local but wider landscape information, such as knowledge about upstream/downstream conditions and residence-time, is needed when designing management measures. Water resources are normally shared by many stakeholders often with opposing objectives. Here, we found that models can have added value for science communication, participatory processes and conflict resolution to reach environmental goals.

It is well known that numerical models are more or less wrong and linked with uncertainties, but nevertheless, models combined with multiple sources of observations can be very helpful to aggregate information, quantify influence from various processes and describe outcome of complex phenomena. From modelling experiments, I will show how we reached deeper understanding of hydrological process when using the landscape perspective and large-sample empirical data across different physiographical conditions. Linking the model to landscape characteristics also gave us the possibility to make water predictions with some confidence even in data sparse regions and for ungauged catchments.

Large-scale modelling of water resources should be accompanied with site-specific data and local knowledge to be applicable for water resources engineering and management. Therefore, we share our model and I will exemplify how we reach a better understanding and make use of new science in collaborative efforts across the globe. Recently, the modelled data was also aggregated into societal-relevant indicators and provided through web-based climate and water services. During co-development of such on-line tools with practitioners, however, we encountered a large knowledge gap between data producers and data users, which calls for mutual engagement to reach understanding.

To sum up, my team uses and provides open data, open science and community building world-wide to accelerate water research by sharing local insights and collective intelligence in addressing multiple landscapes. Yet, scientific knowledge is always preliminary and needs to be challenged by peers and explored by users to be practically beneficial. I therefore advocate for science communication as an emerging field to engage more with. Hydrological scientists have a lot to contribute and learn in dialogues to find hope and solutions under global change, which will help in sustaining the water resources and the Planet as we know it.

How to cite: Arheimer, B.: Landscape perspectives in hydrological understanding and modelling for water management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12778, https://doi.org/10.5194/egusphere-egu21-12778, 2021.

EGU21-1353 | Presentations | MAL14a | Arne Richter Award for Outstanding ECS Lecture 2020

The karst and the furious – ways to keep calm when dealing with karst hydrology

Andreas Hartmann

The dissolution of carbonate rock ‘karstification’ creates pronounced surface and subsurface heterogeneity and results in complex flow and transport dynamics. Consequently, water resources managers face significant challenges keeping calm when dealing with karst water resources especially in times of environmental change. My lecture not only will provide an overview of the peculiarities of karst hydrology but it will also offer some approaches that facilitate the assessment of environmental changes on karst water resources. Using two case studies, one at the plot scale and the other at the scale of an entire continent, I will contrast the opportunities and challenges of dealing with karst across different scales and climatic regions. Along these case studies, I will elaborate (1) how understanding on dominant karst processes can be obtained, (2) how this understanding can be incorporated into karst specific modelling approaches, and (3) how karst models developed at different scales can be used for water management. The presentation will conclude with some thoughts to facilitate less furious implementations of karst approaches for everyone.

How to cite: Hartmann, A.: The karst and the furious – ways to keep calm when dealing with karst hydrology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1353, https://doi.org/10.5194/egusphere-egu21-1353, 2021.

MAL14b – HS 2020/2021 John Dalton Medal Lectures & 2021 Division Outstanding ECS Award Lecture

EGU21-8542 | Presentations | MAL14b | John Dalton Medal Lecture 2020

Hydrology without Dimensions

Amilcare Porporato
 
Dimensional analysis offers an ideal playground to tackle complex hydrological problems. The powerful dimension reduction, in terms of governing dimensionless groups, afforded by the PI-theorem and the related self-similarity arguments is especially fruitful in case of nonlinear models and complex datasets. After briefly reviewing these main concepts, in this lecture I will present several applications ranging from hydrologic partitioning (Budyko's curve) and stochastic ecohydrology, to global weathering rates and soil formation, as well as landscape evolution and channelization. Since Copernicus-dot-org asks me to add at least 25 words to the abstract, I would like to thank the colleagues who supported my nomination for the Dalton medal and my many collaborators.

How to cite: Porporato, A.: Hydrology without Dimensions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8542, https://doi.org/10.5194/egusphere-egu21-8542, 2021.

EGU21-428 | Presentations | MAL14b | John Dalton Medal Lecture 2021

A (not so) random walk through hydrological space and time

Brian Berkowitz

A key philosophical perspective in science is that nature obeys general laws. Identification of these laws involves integration of system conceptualization, observation, experimentation and quantification. This perspective was a guiding principle of John Dalton’s research as he searched for patterns and common behaviors; he performed a broad range of experiments in chemistry and physics, and he entered over 200,000 observations in his meteorological diary during a period of 57 years. In this spirit, we examine general concepts based largely on statistical physics – universality, criticality, self-organization, and the relationship between spatial and temporal measures – and demonstrate how they meaningfully describe patterns and processes of fluid flow and chemical transport in hydrological systems. We discuss examples that incorporate random walks, percolation theory, fractals, and thermodynamics in analyses of hydrological systems – aquifers, soil environments and catchments – to quantify what appear to be universal dynamic behaviors and characterizations.

How to cite: Berkowitz, B.: A (not so) random walk through hydrological space and time, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-428, https://doi.org/10.5194/egusphere-egu21-428, 2021.

EGU21-9208 | Presentations | MAL14b | HS Division Outstanding ECS Award Lecture 2021

Putting humans in the loop: coupling behavioral modeling with natural systems' models

Matteo Giuliani

Natural systems’ models have done tremendous progress in accurately reproducing a large variety of physical processes both in space and time. Conversely, despite human footprint is increasingly recognized as a major driver of undergoing global change, human behaviors and their interactions with natural processes still remain oversimplified in many models supporting strategic policy design. Recent years have seen an increasing interest and effort by scientists in quantitatively characterizing the co-evolution of nature and society. Nevertheless, state-of-the-art models often relies on behavioral rules empirically defined or derived by general social science or economic studies, which lack proper formalization for the specific case study as well as validation against observational data.

In this talk I will discuss my experiences in modeling human behaviors by taking advantage of the unprecedented amount of information and data nowadays available and of the improvements in machine learning and optimization algorithms. The resulting decision-analytic behavioral models flexibly blend descriptive models, which derive if-then behavioral rules specifying human actions in response to external stimuli, and normative models, which assume fully rational behaviors and provide optimal decisions maximizing a given utility function, where the ultimate goal is not to support optimal decisions but, rather, to understand and model human decisions and behaviors at different spatial and temporal scales.

A number of real world examples in the water domain will be used to provide a synthesis of recent advances in behavioral modeling and to stimulate discussion on key challenges, such as the role of individual behavioral factors in modeling decisions under uncertainty, the scalability of the models for capturing heterogenous behaviors, the definition of model’s boundaries, the identification of behavioral preferences in terms of tradeoff among multiple competing objectives and the dynamic evolution of this tradeoff driven by extreme hydroclimatic events.

How to cite: Giuliani, M.: Putting humans in the loop: coupling behavioral modeling with natural systems' models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9208, https://doi.org/10.5194/egusphere-egu21-9208, 2021.

MAL15a – NH 2021 Plinius Medal Lecture & 2020 Sergey Soloviev Medal Lecture & 2020 Division Outstanding ECS Award Lecture

EGU21-241 | Presentations | MAL15a | Plinius Medal Lecture 2021

Natural Hazards: from Plinius’ time to the Anthropocene

Giuliano Di Baldassarre

Plinius (23-79 AD) is known worldwide as the author of the encyclopedic Naturalis Historia. He died in Stabiae while trying to rescue his family from the eruption of Mount Vesuvius, one of the deadliest volcanic eruptions in European history that also destroyed the cities of Herculaneum and Pompeii. At that time, natural hazards were mostly seen as “acts of God(s)”. Instead, in today’s Anthropocene, extreme events coexist with two dichotomic (and rather simplistic) views: “disasters are natural” vs. “humans are to blame since they live in risky areas”. In this lecture, I present scientific and societal challenges associated with the increasing impact (from Plinius’ time to the Anthropocene) of humans on the spatial and temporal distribution of natural hazards. I also problematize and challenge myths, preconceptions and conventional wisdoms related with uncertainty, behavioral heuristics, expert vs. local knowledge, social power and inequalities. To this end, I review recent studies in various socioeconomic contexts, and across multiple hazards, with a focus on five events that have significantly influenced my research work: the 1963 Vajont Dam landslide, the 2004 flooding in Haiti and the Dominican Republic, the 2009 L’Aquila earthquake, the water crisis (Day Zero) during the 2015-2017 drought in Cape Town and the ongoing COVID-19 pandemic.

How to cite: Di Baldassarre, G.: Natural Hazards: from Plinius’ time to the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-241, https://doi.org/10.5194/egusphere-egu21-241, 2021.

EGU21-16282 | Presentations | MAL15a | NH Division Outstanding ECS Award Lecture 2020

Global Seismic Risk Assessment: the Wrong, the Right, and the Truth.

Vitor Silva

The increase in the global population, climate change, growing urbanization and settlement in regions prone to natural hazards are some of the factors contributing to the increase in the economic and human losses due to disasters. Earthquakes represent on average approximately one-fifth of the annual losses, but in some years this proportion can be above 50% (e.g. 2010, 2011). This impact can affect the sustainable development of society, creation of jobs and availability of funds for poverty reduction. Furthermore, business disruption of large corporations can result in negative impacts at global scale. Earthquake risk information can be used to support decision-makers in the distribution of funds for effective risk mitigation. However, open and reliable probabilistic seismic risk models are only available for less than a dozen of countries, which dampers disaster risk management, in particular in the under-developed world. To mitigate this issue, the Global Earthquake Model Foundation and its partners have been supporting regional programmes and bilateral collaborations to develop an open global earthquake risk model. These efforts led to the development of a repository of probabilistic seismic hazard models, a global exposure dataset, and a comprehensive set of fragility and vulnerability functions for the most common building classes. These components were used to estimate relevant earthquake risk metrics, which are now publicly available to the community.

The development of the global seismic risk model also allowed the identification of several issues that affect the reliability and accuracy of existing risk models. These include the use of outdated exposure information, insufficient consideration of all sources of epistemic and aleatory uncertainty, lack of results regarding indirect human and economic losses, and inability to forecast detailed earthquake risk to the upcoming decades. These challenges may render the results from existing earthquake loss models inadequate for decision-making. It is thus urgent to re-evaluate the current practice in earthquake risk loss assessment, and explore new technologies, knowledge and data that might mitigate some of these issues. A recent resource that can support the improvement of exposure datasets and the forecasting of exposure and risk into the next decades is the Global Human Settlement Layer, a collection of datasets regarding the built-environment between 1974 and 2010. The consideration of this type of information and incorporation of large sources of uncertainty can now be supported by artificial intelligence technology, and in particular open-source machine learning platforms. Such tools are currently being explored to predict earthquake aftershocks, to estimate damage shortly after the occurrence of destructive events, and to perform complex calculations with billions of simulations. These are examples of recent resources that must be exploited for the benefit of improving existing risk models, and consequently enhance the likelihood that risk reduction measures will be efficient.

This study presents the current practice in global seismic risk assessment with all of its limitations, it discusses the areas where improvements are necessary, and presents possible directions for risk assessment in the upcoming years.

How to cite: Silva, V.: Global Seismic Risk Assessment: the Wrong, the Right, and the Truth., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16282, https://doi.org/10.5194/egusphere-egu21-16282, 2021.

EGU21-1826 | Presentations | MAL15a | Sergey Soloviev Medal Lecture 2020

Limitations in the Use of Past Datasets for Future Hazard Analysis 

John Clague

Frequency-magnitude relations derived from historic and prehistoric datasets underpin many natural hazard risk assessments. For example, probabilistic estimates of seismic risk rely on instrumented records of past earthquakes, in some cases supplemented by prehistoric seismicity inferred from proxy geologic evidence. Yet, there are several problems in these datasets that compromise the reliability of derived frequency-magnitude relations. In this presentation, I briefly discuss these problems. First, historic records of past events are temporally biased. Using seismicity as an example, earthquake catalogues are complete only for the past several decades, the period during which seismic networks have been sufficiently extensive to capture all events. During the first half of the twentieth century, small and even moderate earthquakes went unrecorded, and farther back in time, the occurrence of even large earthquakes is limited to eyewitness accounts. Prior to the last century, there is only limited knowledge of rare, but large events with low average return periods. Yet, low social and political tolerance for risk requires knowledge of events with return periods of hundreds to thousands of years. Temporal biases of this type result in huge uncertainties about the future occurrence of events with large return periods. A second limitation, which applies particularly to prehistoric events, is the large uncertainty in the times and magnitudes of events inferred using geologic proxy data. The example I use in this talk is the large debris-flow prone Cheekye River fan in southwestern British Columbia. Relatively small debris flows have happened on the fan in the historic period, and there is geologic evidence for several much larger prehistoric events during the Holocene. A new residential subdivision has been proposed for the apex of the fan, requiring that geologists estimate the sizes of debris flows with return periods up to 10,000 years. The Cheekye fan has been better studied than any other fan in western Canada, yet there are very large uncertainties in the sizes and times of events that are more than 100 years old. Event times are imprecise because radiocarbon ages carry inherent uncertainties of several decades to centuries. Furthermore, the geologic record of past events is incomplete. The frequency-magnitude curve for debris flows on Cheekye fan is ‘better than nothing’, but the very low societal tolerance for risk in Canada means that decisions about development on the fan likely will be based on worst-case scenarios of long return-period events that are poorly grounded in science. A third limitation that I highlight in my presentation pertains to weather-related hazards (floods, severe storms, and many landslides). An assumption made when using frequency-magnitude relations to evaluate hazard and risk is that the past can be applied to the near-future. This assumption is invalid for weather-related hazards, because climate is changing. Climate non-stationarity implies, for example, that historic hydrometric data, upon which flood frequency analyses were based in the past century may be of limited use in planning for future extreme floods.

How to cite: Clague, J.: Limitations in the Use of Past Datasets for Future Hazard Analysis , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1826, https://doi.org/10.5194/egusphere-egu21-1826, 2021.

MAL15b – NH 2020 Plinius Medal Lecture & 2021 Sergey Soloviev Medal Lecture & 2021 NH Division Outstanding ECS Award Lecture

EGU21-641 | Presentations | MAL15b | Sergey Soloviev Medal Lecture 2021

Considerations on the prediction of hazards (mainly landslides) and their consequences

Fausto Guzzetti

The general assumptions and the most popular methods used to assess landslide hazard and for landslide risk evaluation have not changed significantly in recent decades. Some of these assumptions have conceptual weaknesses, and the methods have revealed weackneses and limitations. After an introduction on what we need to predict in order to assess landslide hazard and risk, I introduce the strategies and main methods currently used to detect and map landslides, to predict landslide populations in space and time, and to anticipate the number and size characteristics of expected landslides. For landslide detection and mapping, I consider traditional methods based on visual interpretation of aerial photography, and modern approaches that exploit visual, semi-automatic or automatic analysis of remotely sensed imagery. For spatial landslide prediction, I discuss the results of a review of classification-based statistical methods for evaluating landslide susceptibility. For temporal forecasting, drawing on a review of geographical landslide forecasting and early warning systems, I discuss short-term forecasting capabilities and their limitations. Then, I discuss the long-term landslide projections considering the impact of climate variations on landslide projections. Regarding the numerosity and size of landslides, I discuss existing statistics on the length, width, area, and volume of landslides obtained from populations of event-triggered landslides. This is followed by an analysis of the consequences of landslides. I conclude by offering recommendations on what I imagine we should do to make significant progress in our collective ability to predict the risk posed by landslide populations and to mitigate their risk. My understanding, but also my feeling and hope, is that some - perhaps many - of the recommendations are general, and may be applicable to other hazards as well.

How to cite: Guzzetti, F.: Considerations on the prediction of hazards (mainly landslides) and their consequences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-641, https://doi.org/10.5194/egusphere-egu21-641, 2021.

EGU21-2215 | Presentations | MAL15b | NH Division Outstanding ECS Award Lecture 2021

Infrastructure opportunities for the resilience of tomorrow’s cities

Maria Pregnolato

The world evolves. Cities have become the most common human settlement (>50% world population is urban). They act as major centres of economic activity and innovation, but also as hubs of crucial challenges. Cities are increasingly complex systems which have to address the enhanced demand, as well as sustainability criteria (e.g. meeting the 2015 Paris Climate Agreement target). Cities are also increasingly suffering from the impact of extreme weather, which are expected to threat US$4 trillion of assets by 2030 [1].

Science evolves too. New technology (e.g. Internet of Things) and concepts (e.g. smart cities) are emerging to manage risks and develop strategies for climate mitigation and adaptation. Infrastructure plays a core role in developing urban resilience, since they underpin all the key activities and constitute the backbone of a city. When infrastructure is robust and able to adapt, the whole city becomes less vulnerable to natural disasters.

Yet urban research does not fully fulfil the need of decision-makers: existing studies are mostly silo-based (e.g. based on single disciplines), or provide little scope for a business case, or do not offer platforms of practical implementation. Also, the uptake of developed technology (which requires specific expertise) is sometimes difficulty and seen as a further barrier.

This award lecture will review the major challenges that cities are facing today, and illustrate available tools to assess impact to infrastructure, alongside adaptation and technology options. Various international case studies will be presented regarding flooding and road networks [2, 3, 4, 5].

In the future, research and practice needs to interlink to innovate urban policy for mitigating urban climate change and adapting. Cities have never had so many and powerful tools available to tackle their challenges: while there is an immense potential, its realisation is still to unfold. The next decades are critical for developing schemes that address climate and sustainability goals, which could be solely successful with the application of latest science to practical contingencies.

Reference

[1] X Bai, RJ Dawson, D Ürge-Vorsatz, GC Delgado, AS Barau, S Dhakal, et al. (2018). Six research priorities for cities and climate change. Nature 555 (7694), 23-25. https://doi.org/10.1038/d41586-018-02409-z

[2] M Pregnolato, A Ford, V Glenis, S Wilkinson, R Dawson (2017). Impact of climate change on disruption to urban transport networks from pluvial flooding. Journal of Infrastructure Systems 23 (4), 04017015. https://doi.org/10.1061/(ASCE)IS.1943-555X.0000372

[3] C Arrighi, M Pregnolato, RJ Dawson, F Castelli (2019). Preparedness against mobility disruption by floods. Science of the Total Environment 654, 1010-1022. https://doi.org/10.1016/j.scitotenv.2018.11.191

[4] C Arrighi, M Pregnolato, F Castelli (2020). Indirect flood impacts and cascade risk across interdependent linear infrastructures. Natural Hazards and Earth System Sciences Discussions, 1-18. https://doi.org/10.5194/nhess-2020-371

[5] M Pregnolato, AO Winter, D Mascarenas, AD Sen, P Bates, MR Motley (2020). Assessing flooding impact to riverine bridges: an integrated analysis. Natural Hazards and Earth System Sciences Discussions, 1-18. https://doi.org/10.5194/nhess-2020-375

How to cite: Pregnolato, M.: Infrastructure opportunities for the resilience of tomorrow’s cities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2215, https://doi.org/10.5194/egusphere-egu21-2215, 2021.

The eruption of Mount St. Helens in 1980 exposed a large population to volcanic ash that was found to contain cristobalite – a crystalline silica polymorph and known carcinogen. This event triggered an array of epidemiological, toxicological and geochemical studies to assess the toxicity of ash, marking the birth of a new field of research. This talk will take you on an interdisciplinary journey through the work conducted since the 1980s, which has discovered both biological mechanisms in favour of volcanic ash toxicity and inherent physicochemical characteristics of ash particles that may render the silica surfaces non-toxic. A sparsity of longitudinal clinical and epidemiological studies following eruptions means that medical evidence for chronic ash pathogenicity is lacking, but other research has shown that acute exposures to volcanic ash can exacerbate existing respiratory conditions. Additionally, a multitude of techniques and protocols have been developed for rapid, eruption-specific health hazard assessment, but conducting these assessments in a crisis is very challenging. In the absence of definitive information about the harmfulness of ash, many exposed people choose to protect themselves as a precaution, or are advised to do so by agencies, so recent research has focussed on providing them with the knowledge to do that effectively. This laboratory and community-based research, involving collaborations among geoscientists, exposure scientists, social scientists, medical ethicists, agency and community representatives, has yielded critical insight into a chain of communication from researcher, through various local ‘authorities’, to the actions taken by communities. The findings have led to changes in humanitarian and individual practice and have opened up new pathways to effective uptake of evidence-based advice through co-designed informational products.

How to cite: Horwell, C.: The health hazards and impacts of volcanic ash: an interdisciplinary journey towards effective mitigation, protection and communication, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-497, https://doi.org/10.5194/egusphere-egu21-497, 2021.

MAL16 – NP 2020/2021 Lewis Fry Richardson Medal Lectures & Division Outstanding ECS Award Lectures

EGU21-1828 | Presentations | MAL16 | Lewis Fry Richardson Medal Lecture 2020

A New Mathematical Framework for Atmospheric Blocking Events

Valerio Lucarini

We use a simple yet Earth-like atmospheric model to propose a new framework for understanding the mathematics of blocking events, which are associated with low frequency, large scale waves in the atmosphere. Analysing error growth rates along a very long model trajectory, we show that blockings are associated with conditions of anomalously high instability of the atmosphere. Additionally, the lifetime of a blocking is positively correlated with the intensity of such an anomaly, against intuition. In the case of Atlantic blockings, predictability is especially reduced at the onset and decay of the blocking, while a relative increase of predictability is found in the mature phase, while the opposite holds for Pacific blockings, for which predictability is lowest in the mature phase. We associate blockings to a specific class of unstable periodic orbits (UPOs), natural modes of variability that cover the attractor of the system. The UPOs differ substantially in terms of instability, which explains the diversity of the atmosphere in terms predictability. The UPOs associated to blockings are indeed anomalously unstable, which leads to them being rarely visited. The onset of a blocking takes place when the trajectory of the system hops into the neighbourhood of one of these special UPOs. The decay takes place when the trajectory hops back to the neighbourhood of usual, less unstable UPOs associated with zonal flow. This justifies the classical Markov chains-based analysis of transitions between weather regimes. The existence of UPOs differing in the dimensionality of their unstable manifold indicates a very strong violation of hyperbolicity in the model, which leads to a lack of structural stability. We propose that this is could be a generic feature of atmospheric models and might be a fundamental cause behind difficulties in representing blockings for the current climate and uncertainties in predicting how their statistics will change as a result of climate change.

References:
V. Lucarini, A. Gritsun, A. A new mathematical framework for atmospheric blocking events. Climate Dynamics 54, 575–598 (2020). https://doi.org/10.1007/s00382-019-05018-2
M. Ghil, V. Lucarini, The Physics of Climate Variability and Climate, Rev. Modern Physics, 92, 035002 (2020). https://link.aps.org/doi/10.1103/RevModPhys.92.035002  
S. Schubert, V. Lucarini, Dynamical analysis of blocking events: spatial and temporal fluctuations of covariant Lyapunov vectors. Q. J. R. Meteorol. Soc. 142, 2143-2158 (2016). https://doi.org/10.1002/qj.2808

How to cite: Lucarini, V.: A New Mathematical Framework for Atmospheric Blocking Events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1828, https://doi.org/10.5194/egusphere-egu21-1828, 2021.

EGU21-552 | Presentations | MAL16 | NP Division Outstanding ECS Award Lecture 2020

Soliton turbulence in weakly nonlinear and weakly dispersive media

Ekaterina Didenkulova

A short review on weakly nonlinear and weakly dispersive dynamics of soliton ensembles, the so-called soliton turbulence is given. Such processes take place in shallow water waves, internal waves in the atmosphere and the ocean, solid mechanics and astrophysical plasma; they are described by the integrable models of Korteweg – de Vries equation type (modified Korteweg – de Vries equation, Gardner equation). Here, soliton turbulence means an ensemble of solitons with random parameters. The property of solitons to interact elastically with each other gives rise to an obvious association with the gas of elastically colliding particles. Strictly speaking, soliton turbulence (soliton gas) is a deterministic dynamical system due to the integrability of equations describing the evolution of waves (solitons). However, due to the great complexity of its behavior (due to the large number of participating solitons and nonlinear nature of their interactions), the dynamics of the system can be considered random and, accordingly, may be investigated using methods typical for such problems.

Firstly, pair soliton collisions have been analyzed as an elementary act of the soliton turbulence for further understanding of their impact on multi-soliton dynamics. Different types of solitons have been considered: “thick” or “top-table” solitons, algebraic solitons, solitons of different polarities. From the point of view of the turbulence theory, the interactions of waves (particles) should be described by the statistical moments of the wave field. It was shown that the interaction of solitons of the same polarity leads to a decrease in the third and fourth moments characterizing the skewness and kurtosis. However, the interaction of solitons of different polarity leads to an increase in these moments of the soliton field. Then, the study of collision patterns of breathers (localized oscillating packets) with each other and with solitons has been carried out. The determination of conditions leading to an extreme scenario, as well as statistical properties, probability and features of large wave manifestation has been provided. As a result of numerical modeling of the multi-soliton field dynamics, the appearance of anomalously large waves in bipolar soliton fields has been demonstrated. Though most of the soliton collisions occur between the pairs of solitons, which may result in maximum two-fold wave amplification, multiple collisions also happen (they make about 10% of the total number of collisions). The long-term simulation of the soliton gas dynamics has shown a significant decrease in skewness and significant increase in kurtosis, confirming the fact of abnormally large wave (so-called “freak/rogue wave”) occurrence.

The reported study was funded by RFBR according to the research projects 19-35-60022 and 21-55-15008.

How to cite: Didenkulova, E.: Soliton turbulence in weakly nonlinear and weakly dispersive media, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-552, https://doi.org/10.5194/egusphere-egu21-552, 2021.

EGU21-456 | Presentations | MAL16 | Lewis Fry Richardson Medal Lecture 2021

How many modes does it take to describe climate change?: The lessons from an experiment

Berengere Dubrulle

According to everyone's experience, predicting the weather reliably for more than 8 days seems an impossible task for our best weather agencies. At the same time, politicians and citizens are asking scientists for decades of climate predictions to help them make decisions, especially on CO2 emissions. To what extent is this request scientifically admissible?

 

In this lecture I will investigate this question, focusing on the topic of predictions of bifurcations of the atmospheric or oceanic circulations. In such case, the issue is whether present climate models, that have necessarily a finite resolution and a smaller number of degrees of freedom than the actual terrestrial systems, are able to reproduce spontaneous or forced bifurcations. For this, I will use recent results obtained by my group in a laboratory analog of such systems, so called von Karman flow, in which spontaneous bifurcations of the circulation take place. I will detail the analogy, and investigate the nature of bifurcations, the number of degrees of freedom that characterizes it and discuss what is the effect of reducing the number of degrees of freedom in such system.

I will also discuss the role of fluctuations and their origin, and stress the importance of describing very small scales to capture fluctuations of correct intensity and scale.

How to cite: Dubrulle, B.: How many modes does it take to describe climate change?: The lessons from an experiment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-456, https://doi.org/10.5194/egusphere-egu21-456, 2021.

EGU21-357 | Presentations | MAL16 | NP Division Outstanding ECS Award Lecture 2021

Critical transitions in Earth system dynamics

Niklas Boers

It has been argued that several components of the Earth system may destabilise in response to gradually changing forcing such as rising atmospheric greenhouse gas concentrations and temperatures. Key examples of potentially unstable parts of the Earth system include the polar ice sheets and sea ice cover, the Atlantic Meridional Overturning Circulation, as well as tropical rainforests and monsoon systems. There are reasons to believe that the leading dynamical modes of these subsystems may essentially mimic bifurcations in low-order random dynamical systems. The stability loss on the way to critical transitions associated with such bifurcations typically leaves characteristic imprints in the statistics of time series encoding the dynamics of the system in question, which can hence serve as a proxy to assess the stability of the system. Here, we present recent advances in detecting stability loss along these lines and investigate proxy reconstructions and observations of several of the Earth system components that have been proposed to be at risk of destabilisation. We discuss the control parameters relevant for the different Earth system components and report on the posterior distributions of the critical thresholds, beyond which stability would be lost. 

How to cite: Boers, N.: Critical transitions in Earth system dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-357, https://doi.org/10.5194/egusphere-egu21-357, 2021.

MAL17 – OS 2020/2021 Fridtjof Nansen Medal Lectures & 2021 Division Outstanding ECS Award Lecture

EGU21-440 | Presentations | MAL17 | Fridtjof Nansen Medal Lecture 2020

From the North Atlantic Oscillation to the Tropics and back...

Richard Greatbatch

We start with the severe European winter of 1962/63, a winter when the North Atlantic Oscillation (NAO) index was strongly negative with persistent easterly wind anomalies across northern Europe and the British Isles. We then note that the NAO is a manifestation of synoptic Rossby wave breaking. The positive feedback with which synoptic eddies act to maintain the atmospheric jet stream against friction turns out to also be the mechanism by which the equatorial deep jets in the ocean are maintained against dissipation. We were fortunate to be able to demonstrate this in both a simple model set-up that supports deep jets and directly from mooring data at 23 W on the equator in the Atlantic Ocean. The deep jets offer some potential for prediction over the neighbouring African continent on interannual time scales. This then leads to a discussion of the importance of the tropics for prediction on both seasonal and decadal time scales and longer, linking back to the winter of 1962/63.  A simple statistical model is used to illustrate many features of predictability, including non-stationarity and the so-called signal to noise paradox.

How to cite: Greatbatch, R.: From the North Atlantic Oscillation to the Tropics and back..., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-440, https://doi.org/10.5194/egusphere-egu21-440, 2021.

EGU21-5271 | Presentations | MAL17 | OS Division Outstanding ECS Award Lecture 2021

How does the Arctic affect North Atlantic climate? Fresh perspectives on a long-standing question.

Marilena Oltmanns, N. Penny Holliday, James Screen, D. Gwyn Evans, Simon A. Josey, Ben Moat, Johannes Karstensen, and G. W. Kent Moore

Recent decades have been characterised by amplified Arctic warming and increased occurrence of extreme weather events in the North Atlantic region. While earlier studies noticed statistical links between high-latitude warming and mid-latitude weather extremes, the underlying dynamical connections remained elusive. Combining different data products, I will demonstrate a new mechanism linking Arctic ice losses with cold anomalies and storms in the subpolar region in winter, and with heat waves and droughts over Europe summer. Considering feedbacks of the identified mechanism on the Arctic Ocean circulation, I will further present new support for the potential of Arctic warming to trigger a rapid change in climate.

How to cite: Oltmanns, M., Holliday, N. P., Screen, J., Evans, D. G., Josey, S. A., Moat, B., Karstensen, J., and Moore, G. W. K.: How does the Arctic affect North Atlantic climate? Fresh perspectives on a long-standing question., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5271, https://doi.org/10.5194/egusphere-egu21-5271, 2021.

The Joint Global Ocean Flux Study (JGOFS) started in 1987 and stimulated massive integration of efforts to measure and understand the processes of downward flux in the ocean. A small number of sustained observatories have persisted from this time in the belief that a key to gaining this understanding is by prolonged time-series observations. The sustained observatory over the Porcupine Abyssal Plain (PAP-SO) in the Northeast Atlantic is one such site which has provided nearly continuous measurements of downward flux at a depth of 3000m since 1989. This was using sediment traps but, in order to understand the data, we have exploited a wide range of other approaches such as optical methods, drifting sediment traps in the upper 1000m, chemical variables near the surface and computational modelling. Insights are also gained from the Continuous Plankton Recorder (CPR), satellite observations and various climatic indices.

This presentation draws together these measurements to quantify and understand flux at 3000m. Seasonal and interannual variability is large but after 30 years of observation, explanations are now possible. In addition, some of the conclusions identify major and surprising features about the ways ecosystems in one year may be influenced by their structure and function in previous years.

At the same time as these time-series observations have been in progress, major new developments have taken place globally and at PAP-SO to provide additional and alternative means to asses flux. The sediment trap has significant advantages as well as uncertainties which have been described previously. The new era of approaches using, for instance, BGC Argo, the Carbon Flux Explorer and a variety of other optical techniques offer what may be a quantum leap in our understanding of downward particle flux now and how it is changing in response to changes in the global climate. This presentation will give a personal and optimistic view of the opportunities which are now developing to quantify and understand this crucially important process.

How to cite: Lampitt, R.: Downward particle flux in the open ocean: Future global opportunities and insights from time-series measurements at the PAP Sustained Observatory in the Northeast Atlantic., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15591, https://doi.org/10.5194/egusphere-egu21-15591, 2021.

MAL18 – PS 2020 David Bates Medal Lecture & 2021 Division Outstanding ECS Award Lecture

EGU21-407 | Presentations | MAL18 | David Bates Medal Lecture 2020

Jupiter’s Great Red Spot

Agustin Sanchez-Lavega

Jupiter’s Great Red Spot (GRS), is a giant anticyclone, the largest and longest-lived of all the vortices observed in planetary atmospheres. Perhaps observed for the first time in the 17th century, during its history, the length of the GRS has shrunk since 1879 from ~ 40,000 km to 15,000 km in 2020. The GRS is distinguished in the disk of Jupiter as an oval of intense red color, although this coloration changes in time depending on the interactions it undergoes with the meteorological formations and disturbances that flow in its surroundings. The maximum tangential rotation velocity is reached at the periphery of the oval with values from 120 ms-1 in 1979 to 150 ms-1 in 2020, decreasing gradually to the center of the vortex. The GRS, embedded within two jets that oppose in direction, oscillates in longitude with respect to its mean value with a period of 90 days and amplitude of 1°. In this lecture I will review our current knowledge of the GRS, in particular the structure of upper hazes and cloud, its dynamical properties, as well as ideas and models about its nature. Finally, the GRS will be compared with other Jovian vortices, putting into context their relationship with the jet streams pattern of the planet.

How to cite: Sanchez-Lavega, A.: Jupiter’s Great Red Spot, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-407, https://doi.org/10.5194/egusphere-egu21-407, 2021.

The lecture will be split into two parts:

1. ORBYTS

In the UK, physics faces chronic diversity issues, shortfalls in subject-specialist teachers and 20% lower uptake beyond age 16 than in the 1980s. ORBYTS is a movement that partners researchers with schools to involve school children in active scientific research. Since 2017, ORBYTS has grown to 30 school-researcher partnerships, with 75% of ORBYTS school pupils from groups historically-excluded from physics. While the first research projects were exoplanets focussed, we now have researchers working with schools on: protostellar formation, molecular spectroscopy, planetary science, plasma physics, galaxy characterisation, AI, quasars, supernovae and more.

Through involvement in research and partnerships with relatable science role models, ORBYTS is providing positive change in school students’ attainment and is dispelling harmful stereotypes. Schools involved in the programme at age 14-16 report 100% increases in post-16 uptake of physics by girls and students from more than 40 ethnicities. Since 2017, the programme has enabled more than 150 school students to author published papers.

We welcome contact from anyone interested. We hope to continue to sustainably expand the programme to new researcher-school partnerships that can help make science more inclusive for all.

2. X-ray Observations of the Outer Planets

A revolution is happening in the field of planetary X-rays. In the last few years, there have been unprecedented campaigns totalling hundreds of hours of observations by the flagship NASA and ESA X-ray observatories (Chandra and XMM-Newton). Currently, ground-breaking X-ray instruments are travelling to Mercury on BepiColombo and soon to observe the Earth on the ESA/CAS SMILE spacecraft. This is shifting X-ray studies of planets from an enigmatic niche to an essential component of our multi-waveband exploration of other worlds.

So, what do X-ray images of planets look like and what do they reveal about environments, properties and processes across our solar system? I provide an overview history of the field and highlight recent discoveries, with a particular focus on the outer planets and their moons. This will include recent observations in tandem with NASA’s paradigm-shifting Juno spacecraft, that reveal the physical processes responsible for some of Jupiter’s spectacular auroral displays and bizarre quasiperiodic pulsations. I also touch on the recent discovery of X-ray emissions from Uranus, before looking to what we can expect from the coming years. 

Finally, I connect the two parts of the lecture by showcasing planetary X-ray research by school students.

 

Research Collaborators: Z.Yao, G.Branduardi-Raymont, D.Grodent, G.R.Gladstone, R.Kraft, L.Ray, A.Wibisono, D.Weigt, E.Woodfield, A.Sulaiman, W.Kurth, S.Nulsen, C.Jackman, S.Elliott, G.Hospodarsky, M.Imai, S.Kotsiaros, G.Clark, B.Bonfond, K.Haewsantati, I.J.Rae, H.Manners, P.Rodriguez, J-U.Ness, B.Mauk, R.Ebert, D.X.Pan, B.B.Ni, R.L.Guo, F.Allegrini, R.Desai, S.Bolton, E.McClain, B.Snios, G.Tremblay

ORBYTS Researchers: M.Fuller, H.Osborne, A.Portas, K.Chubb, L.McKemmish, C.Sousa Silva, T.Rivlin, M.Gorman, M.Tessenyi, G.Tinetti, J.Tennyson, J.Holdship, L.Offer, M.Niculescu-Duvaz, T.James, R.Jaworek, R.Meyer, K.Kade, J.Smutna, S.Brannan,  A.Francis, K.Putri, F.Hardy, H.Andrews, M.Rickard, D.De Mijolla, Q.Changeat, B.Edwards, M.Saraf, M.Morvan, S.Wright, A.Updahyay, O.Katz, B.Edwards, R.French, M.Mooney, C-L.Liew-Cain, A.Sheppard, E.Armstrong, G.Yip, F.Azad, J.Sandhu, A.Smith, M.Walach, W.Gould, A.Bader, C.Ho, M.Bakrania, P.Patel, Q.Afghan, W.Somogyi, C.Regan, M.Mahmoud, A.Wibisono, S.Grafton Waters, F.Staples, S.Bentley, C.Watts, I.J.Rae, A.Robson, G.Branduardi-Raymont

How to cite: Dunn, W.: A Lecture in 2 Parts: 1. ORBYTS: Inspirational Research Partnerships for School Students from Historically-Excluded Groups and 2. Extraordinary X-rays from the Outer Planets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11236, https://doi.org/10.5194/egusphere-egu21-11236, 2021.

MAL19 – SM 2021 Beno Gutenberg Medal Lecture & Division Outstanding ECS Award Lecture

EGU21-13755 | Presentations | MAL19 | Beno Gutenberg Medal Lecture 2021

Asking questions of data in nonlinear geophysical inversion

Malcolm Sambridge

For more than half a century, geoscientists have sought new ways to solve inverse problems, which occur when observations only indirectly constrain some property of interest. In the case of geophysics this usually means using surface observations to quantify properties of the Earth hidden from us within its interior, or processes which occurred in the past. Both the target is not directly accessible, and measurements which constrain it are not completely under our control. This is a challenging situation, where the search for new efficient and practical methods of solution to inversion problems has received regular attention.

A convenient way to view inverse problems as a way of asking questions of data. A common class of question might be to ask `Which set of model parameters, within a chosent class, fits a subset of the data best?’  How one measures `best fit’ constitutes a fundamental component of the question being asked. Another example might be `Which probability distribution best describes a `state of knowledge’ about a set of representative parameters?’. As the question changes, naturally so does the solution, even if the data does not. This talk will examine this approach to inversion and explore some new forms of question that can be asked of data. In particular, cases will be examined where the same answer can arise from different style of questions, some of which are much easier to solve than others. A focus will be on optimal model generation in nonlinear cases using data questions based on mathematical ideas from the field of Optimal Transport.

 

How to cite: Sambridge, M.: Asking questions of data in nonlinear geophysical inversion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13755, https://doi.org/10.5194/egusphere-egu21-13755, 2021.

EGU21-5143 | Presentations | MAL19 | SM Division Outstanding ECS Award Lecture 2021

Volcanic Tremor and its Relation to Volcano- and Glacier-related Processes

Eva P. S. Eibl

Volcanic eruptions can affect the climate system, the environment and society. On ice covered volcanoes this threat intensifies due to the increasing explosivity in contact with water. Monitoring and early-warning of such eruptions is closely linked to real-time, multidisciplinary data analysis. This builds on a good understanding and location of the recorded signals.

I will summarize my work on understanding and modelling volcanic tremor, a long-lasting seismic signal with emergent onset. This tremor accompanies various volcano- and glacier-related processes and has to be reliably detected and distinguished from other sources. My examples range from modelling pre-eruptive subglacial tremor and silent magma flow, to monitoring eruptive tremor, to early warning of subglacial flooding, to hydrothermal explosions and boiling and other sources such as helicopters. These results are based on array analysis, amplitude location techniques and single-station arrays but I will also risk a look into the future embracing the emerging field of rotational seismology which might solve some challenges we face in volcanic and glacial environments and advance our understanding and modelling of volcanic signals at remote sites.

How to cite: Eibl, E. P. S.: Volcanic Tremor and its Relation to Volcano- and Glacier-related Processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5143, https://doi.org/10.5194/egusphere-egu21-5143, 2021.

MAL20 – SSP 2020/2021 Jean Baptiste Lamarck Medal Lectures & Division Outstanding ECS Award Lectures

EGU21-574 | Presentations | MAL20 | Jean Baptiste Lamarck Medal Lecture 2020

The evolution of feathers

Michael Benton

Feathers are a diagnostic character of birds, and yet new fossils show they likely originated more than 100 million years before the first birds. In fact, feathers probably occurred in all dinosaur groups, and in their cousins, the pterosaurs, as we showed in 2019. This finding confirms current knowledge of the genomic regulation of feather development. Our work stems from ten years of collaboration with Chinese colleagues, during which we set ourselves the task of understanding fossil feathers. Our first discovery was to answer the question, ‘Will we ever know the colour of dinosaurs?’. In 2010, we were able to announce the first objective evidence for colour in a dinosaur. Using ultrastructural studies of fossil feathers, we identified melanosomes for the first time in dinosaur feathers, and these demonstrated that Sinosauropteryx had ginger and white rings down its tail. Studies of other dinosaurs identified patterns of black, white, grey, brown, and ginger. This is part of a new wave in Palaeobiology where we apply objective approaches to provide testable hypotheses, once thought impossible in the historical sciences.

 

Benton, M.J., Dhouailly, D., Jiang, B.Y., and McNamara, M. 2019. The early origin of feathers. Trends in Ecology & Evolution 34, 856-869 (doi: 10.1016/j.tree.2019.04.018).

https://dinocolour.blogs.bristol.ac.uk/

https://dinosaurs.blogs.bristol.ac.uk/

How to cite: Benton, M.: The evolution of feathers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-574, https://doi.org/10.5194/egusphere-egu21-574, 2021.

EGU21-11904 | Presentations | MAL20 | SSP Division Outstanding ECS Award Lecture 2020

Deep-sea panoramas: Progress and remaining challenges in late Miocene stratigraphy and climate

Anna Joy Drury, Thomas Westerhold, David A. Hodell, Mitchell Lyle, Cédric M. John, Amelia E. Shevenell, Ursula Röhl, and Roy Wilkens

During the late Miocene, meridional sea surface temperature gradients, deep ocean circulation patterns, and continental configurations evolved to a state similar to modern day. Deep-sea benthic foraminiferal stable oxygen (δ18O) and carbon (δ13C) isotope stratigraphy remains a fundamental tool for providing accurate chronologies and global correlations, both of which can be used to assess late Miocene climate dynamics. Until recently, late Miocene benthic δ18O and δ13C stratigraphies remained poorly constrained, due to relatively poor global high-resolution data coverage.

Here, I present ongoing work that uses high-resolution deep-sea foraminiferal stable isotope records to improve late Miocene (chrono)stratigraphy. Although challenges remain, the coverage of late Miocene benthic δ18O and δ13C stratigraphies has drastically improved in recent years, with high-resolution records now available across the Atlantic and Pacific Oceans. The recovery of these deep-sea records, including the first astronomically tuned, deep-sea integrated magneto-chemostratigraphy, has also helped to improve the late Miocene geological timescale. Finally, I will briefly touch upon how our understanding of late Miocene climate evolution has improved, based on the high-resolution deep-sea archives that are now available.

How to cite: Drury, A. J., Westerhold, T., Hodell, D. A., Lyle, M., John, C. M., Shevenell, A. E., Röhl, U., and Wilkens, R.: Deep-sea panoramas: Progress and remaining challenges in late Miocene stratigraphy and climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11904, https://doi.org/10.5194/egusphere-egu21-11904, 2021.

EGU21-1766 | Presentations | MAL20 | Jean Baptiste Lamarck Medal Lecture 2021

Coral meets Milankovitch – or: time-distribution in shallow-marine carbonate sequences  

André Strasser

It is challenging to compare Recent or Holocene accumulation rates of shallow-marine carbonates with accumulation rates interpreted from the fossil sedimentary record. Today, a single coral branch can grow up to 10 cm/year, and vertical accumulation rates may reach 1.4 cm/year if the ecological conditions are favorable for the carbonate-producing organisms and if there is space to accommodate the sediment. However, due to common reworking and transport by waves and currents, and because of potential subaerial exposure, the time-distribution within the sedimentary record is highly irregular.

In ancient carbonate sequences, this time-distribution is difficult to evaluate, and a time-resolution as high as possible has to be sought for. Identification of the record of orbital cycles (Milankovitch cycles) is the best way to obtain a relatively narrow time-window, which in the best case corresponds to the 20-kyr precession cycle. During green-house conditions, orbitally-induced climate cycles translated into more or less symmetrical sea-level cycles, which at least partly controlled sediment production and accumulation. This allows for a sequence-stratigraphic subdivision of each individual depositional sequence. Thus, a time-frame is given for the interpretation of facies evolution and sedimentary structures within such a sequence.

Based on this hypothesis, two examples are presented, both from the Swiss and French Jura Mountains. A 2-m thick (decompacted) Oxfordian sequence displays carbonate-dominated transgressive deposits followed by marl-dominated highstand deposits. The sequence took 20 kyr to build, but sediment accumulation was episodically interrupted by storm events, and a hardground formed during maximum flooding. The maximum rate of sea-level rise is estimated at 30 cm/kyr (which is ten times slower that today’s sea-level rise). The second example is of Berriasian age and shows a 45-cm thick bed of beachrock composed of slabs of oolite. The bed overlies tidal-flat deposits and is capped by a 4-cm thick calcrete crust, over which follows a polymictic conglomerate. According to the cyclostratigraphic analysis, this sequence represents 100 kyr. Ooid production and beachrock formation can happen within a few 100 to a few 1000 years, and the formation of the calcrete took a few 1000 years more. The rest of the time available thus is represented by the transgressive surface at the base of the sequence, by subaerial exposure, and especially by the conglomerate composed of different facies that formed, were cemented, and then were reworked during several 20-kyr cycles.

The conclusion is that, by careful analysis of ancient shallow-marine carbonate sequences and within a cyclostratigraphic framework, depositional processes may be reconstructed and compared with processes that can be observed and quantified in the Holocene and today, and this at comparable time-scales. Thus, a dynamic and realistic picture of the ancient depositional systems is offered.  

How to cite: Strasser, A.: Coral meets Milankovitch – or: time-distribution in shallow-marine carbonate sequences  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1766, https://doi.org/10.5194/egusphere-egu21-1766, 2021.

EGU21-6120 | Presentations | MAL20 | SSP Division Outstanding ECS Award Lecture 2021

Advances in high-resolution paleoclimate reconstructions using growth experiments, age modelling and clumped isotope analyses

Niels de Winter, Rob Witbaard, Inigo Müller, Ilja Kocken, Tobias Agterhuis, Wim Boer, Lennart de Nooijer, Gert-Jan Reichart, Ulrike Wacker, Jens Fiebig, Stijn Goolaerts, and Martin Ziegler

Geochemical records from incremental carbonate archives, such as fossil mollusk shells, contain information on climate and environmental change at the resolution of days to decades (e.g. Schöne and Gillikin, 2013; Ivany, 2012). These high-resolution paleoclimate data, providing snapshots of past climate change on a human scale, complement more conventional reconstructions on a geological timescale of thousands to millions of years. Recent innovations in geochemical techniques such as high-resolution trace element and clumped isotope analyses provide the unique potential to improve the accuracy and resolution of these high-resolution climate reconstructions in the near future (see e.g. de Winter et al., 2020a; b; Caldarescu et al., 2021). However, to be able to make the most out of these new techniques requires a more detailed understanding of the timing and mechanisms of mollusk shell growth as well as the relationship between environment and shell chemistry on daily to weekly timescales.

The UNBIAS (UNravelling BIvAlve Shell chemistry) project combines investigations on lab-grown modern bivalve shells with reconstructions based on fossil shell material from past greenhouse periods in an attempt to improve our understanding of short-term temperature variability in warm climates. Samples from cultured shells labeled with a novel trace element spiking method are used to calibrate accurate temperature reconstructions from bivalve shells using the state-of-the-art clumped isotope method. As a result, we present a temperature calibration of clumped isotope measurements on aragonitic shell carbonates. New statistical routines are developed to accurately date microsamples within shells relative to the seasonal cycle (ShellChron; de Winter, 2020) and to strategically combine these microsamples for seasonal reconstructions of temperature and salinity from fossil shells (seasonalclumped, de Winter et al., 2020c; de Winter, 2021). We present the first results of this integrated seasonal reconstruction approach on fossil bivalve shells from the Pliocene Warm Period and Late Cretaceous greenhouse of northwestern Europe as well as an outlook on future plans within the UNBIAS project.

 

References

Caldarescu, D. E. et al. Geochimica et Cosmochimica Acta 294, 174–191 (2021).

de Winter, N. J. ShellChron v0.2.8: Builds Chronologies from Oxygen Isotope Profiles in Shells. (2020).

de Winter, N. J. seasonalclumped v0.3.2: Toolbox for Seasonal Temperature Reconstructions using Clumped Isotope Analyses. (2021).

de Winter, N. J. et al. Paleoceanography and Paleoclimatology 35, e2019PA003723 (2020a).

de Winter, N. J. et al. Nature Communications in Earth and Environment (in review; 2020b) doi:10.21203/rs.3.rs-39203/v2.

de Winter, N., Agterhuis, T. & Ziegler, M. Climate of the Past Discussions 1–52 (2020c) doi:https://doi.org/10.5194/cp-2020-118.

Ivany, L. C. The Paleontological Society Papers 18, 133–166 (2012).

Schöne, B. R. & Gillikin, D. P. Palaeogeography, Palaeoclimatology, Palaeoecology 373, 1–5 (2013).

How to cite: de Winter, N., Witbaard, R., Müller, I., Kocken, I., Agterhuis, T., Boer, W., de Nooijer, L., Reichart, G.-J., Wacker, U., Fiebig, J., Goolaerts, S., and Ziegler, M.: Advances in high-resolution paleoclimate reconstructions using growth experiments, age modelling and clumped isotope analyses, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6120, https://doi.org/10.5194/egusphere-egu21-6120, 2021.

MAL21 – SSS 2020/2021 Philippe Duchaufour Medal Lectures & Division Outstanding ECS Award Lectures

EGU21-720 | Presentations | MAL21 | SSS Division Outstanding ECS Award Lecture 2020

Soils in a changing world

Sebastian Doetterl

Good time for soil scientists, bad time for soils? Join me at my Soil System Sciences - OECS award lecture where I will highlight how Global Change affects soils across ecosystems and what this means for future plant-soil inter­actions and biogeochemical cycles in a warming, crowded world out of balance.Global Change from the Arctic to the Tropics has accelerated drastically in recent decades, subsequently effecting ecosystems everywhere. Soils and biogeochemical cycling within are no exception. For example, how carbon and nutrients are stabilized in and released from soil is highly affected by changing land use and climate. Despite these changes, soil in earth system models is not represented mechanistically, but rather given a mostly budgetary "black box" function. No methodological framework is available that accounts for the combined effects of climate, geochemistry and disturbance on soil dynamics at larger scales. In addition, most of our process understanding of biogeochemical cycling in soils is derived from data-rich temperate regions. This data has limited applicability in low latitudinal (tropics) or high latitudinal (boreal/subpolar) climate zones, where soils have different properties and drastically different developmental histories.In my talk I will illustrate with a few examples how the gaps in our understanding of soil processes across climate zones and dismissing lateral soil fluxes leads to large uncertainties in predicting future trajectories of the global carbon cycle. I will highlight how the interactions of weathering and disturbance can influence and dominate biogeochemical cycles and microbial processes in soils. I will also discuss some directions where geochemical proxies that are available at the global scale can be useful to model the spatial and temporal patterns of soil carbon storage and turnover.

How to cite: Doetterl, S.: Soils in a changing world, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-720, https://doi.org/10.5194/egusphere-egu21-720, 2021.

EGU21-8289 | Presentations | MAL21 | SSS Division Outstanding ECS Award Lecture 2021

Investigating nutrient controls over microbial activity in tropical soils

Lucia Fuchslueger

The Amazon rainforest is an important sink for atmospheric CO2 counteracting increased emissions from anthropogenic fossil fuel combustion and land use change storing large amounts of carbon in plant biomass and soils. However, large parts of the Amazon Basin are characterized by highly weathered soils (ultisols and oxisols) with low availability of rock-derived phosphorus (and cations), which are mostly occluded in soil or bound in organic matter. Such low phosphorus availability is thought to be (co-)limiting plant productivity. However, much less is known whether low phosphorus availability influences the activity of heterotrophic microbial communities controlling litter and soil organic matter decomposition and thereby long-term carbon sequestration in tropical soils.

In tropical soils high temperature and humid conditions allow overall high microbial activity. Over a larger soil phosphorus fertility gradient across several Amazonian rainforest sites, at low P sites almost 40 % of total P was stored in microbial biomass, highlighting the competitive strength of microorganisms and their importance as P reservoir. Across all sites soil microbial biomass was a significant predictor for soil microbial respiration, but mass-specific respiration rates (normalized by microbial biomass C) rather decreased at higher soil P. Using the incorporation of 18O from labelled water into DNA (i.e., a substrate-independent method) to determine microbial growth, we found significantly lower microbial growth rates per unit of microbial biomass at higher soil P. This resulted in a lower microbial carbon use efficiency, at a narrower C:P stoichiometry in soils with higher P levels, and pointed towards a microbial co-limitation of phosphorus and carbon at low soil P levels. Furthermore, data from a multi-year nutrient manipulation experiment in French Guiana and from short-term lab incubations suggest that microbial communities thriving at low P levels are highly efficient in taking up and storing added P, but do not necessarily respond with increased growth.

Soil microbial communities play a crucial role in soil carbon and phosphorus cycling in tropical soils as potent competitors for available P. They also play an important role in storing and buffering P losses from highly weathered tropical soils. The potential non-homoeostatic stoichiometric behavior of microbial communities in P cycling is important to consider in soil and ecosystem models based on stoichiometric relationships.

How to cite: Fuchslueger, L.: Investigating nutrient controls over microbial activity in tropical soils, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8289, https://doi.org/10.5194/egusphere-egu21-8289, 2021.

EGU21-14580 | Presentations | MAL21 | Philippe Duchaufour Medal Lecture 2020

Additional carbon stabilization in temperate subsoils impeded by biogeochemical and hydraulic constraints

Georg Guggenberger, Patrick Liebmann, Robert Mikutta, Karsten Kalbitz, Patrick Wordell-Dietrich, Timo Leinemann, Sebastian Preusser, Jörg Bachmann, Axel Don, Ellen Kandeler, Bernd Marschner, and Frank Schaarschmidt

Formation of mineral-associated organic matter (MAOM) is a decisive process in the stabilization of OM against rapid microbial decomposition and thus in the soils’ role as global carbon (C) sink. Sorption experiments of dissolved OM (DOM) repeatedly showed that particularly mineral subsoils have a large sorption capacity to retain more C. However, there is also an increasing body of literature, revealing an increasing output of dissolved organic C (DOC) from soils. Here, we investigated into this paradox in forest soil under beech by a combination of a field labelling experiment with 13C-enriched litter with a unique DO13C and 13CO2 monitoring, an in-situ C exchange experiment with 13C-coated minerals, and batch sorption experiments.

Within two years of 13C monitoring, only 0.5% of litter-derived DO13C entered the subsoil, where it was only short-term stabilized by formation of MAOM but prone to fast microbial mineralization. The 13C monitoring, sorption/desorption experiments in the laboratory, and also the in-situ C exchange on buried soil minerals revealed that there is a frequent exchange of DOM with native OM and a preferential desorption of recently retained OM. Hence, there appeared to be a steady-state equilibrium between C input and output, facilitated by exchange and microbial mineralization of an adopted microbial community. The remobilized OM was also richer in less sorptive carbohydrates. Along with transport of most of DOM along preferential paths, this further increased the discrepancy between laboratory-measured sorption capacities of subsoil and the actual C loading of minerals. Finally, the 13C labeling experiments revealed that input of fresh litter-derived OM into subsoil may even mobilize old-soil derived OM. Hence, in the field different biogeochemical constraints are acting that prevent that the laboratory-based C sink can be reached in the field.  We conclude, that forest subsoils can hardly be considered as additional C sink, even at management options that increase DOC input to subsoil.

How to cite: Guggenberger, G., Liebmann, P., Mikutta, R., Kalbitz, K., Wordell-Dietrich, P., Leinemann, T., Preusser, S., Bachmann, J., Don, A., Kandeler, E., Marschner, B., and Schaarschmidt, F.: Additional carbon stabilization in temperate subsoils impeded by biogeochemical and hydraulic constraints, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14580, https://doi.org/10.5194/egusphere-egu21-14580, 2021.

EGU21-435 | Presentations | MAL21 | Philippe Duchaufour Medal Lecture 2021

Impact of Environmental Change on Biogeochemical Cycling in Soil Systems

Donald Sparks

Environmental change, particularly the impact of climate change, is having a profound impact on humankind. Rising seas and temperatures are causing increasing flooding and melting of ice and permafrost soils. The impact of these processes on biogeochemical cycling of metals, carbon, and nutrients in soils and water is not well understood. For example, how do rising seas, which cause inundation of soils with saline water, followed by retrenchment, and salinization of groundwater, affect cycling of redox active elements such as arsenic and iron as well as nutrients such as phosphorus.  Complexation of carbon with iron-bearing minerals is a major mechanism for carbon retention. Under changing climatic conditions, how will carbon cycling be impacted, particularly in permafrost soils, which are sinks for a large portion of terrestrial carbon? This presentation will explore these questions, and others, over a range of spatial and temporal scales.

How to cite: Sparks, D.: Impact of Environmental Change on Biogeochemical Cycling in Soil Systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-435, https://doi.org/10.5194/egusphere-egu21-435, 2021.

MAL22 – ST 2020 Hannes Alfvén Medal Lecture & 2021 Julius Bartels Medal Lecture & 2020 Division Outstanding ECS Award Lecture

EGU21-850 | Presentations | MAL22 | ST Division Outstanding ECS Award Lecture 2020

Explicit IMF By-dependence in geomagnetic activity

Lauri Holappa, Timo Asikainen, and Kalevi Mursula

The interaction of the solar wind with the Earth’s magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the interplanetary magnetic field (IMF). Most solar wind coupling functions quantify this dependence on the IMF orientation with the so-called IMF clock angle in a way, which is symmetric with respect to the sign of the By component. However, recent studies have shown that IMF By is an additional, independent driver of high-latitude geomagnetic activity, leading to higher (weaker) geomagnetic activity in Northern Hemisphere (NH) winter for By > 0 (By < 0). For NH summer the dependence on the By sign is reversed. We quantify the size of this explicit By-effect with respect to the solar wind coupling function, both for northern and southern high-latitude geomagnetic activity. We show that for a given value of solar wind coupling function, geomagnetic activity is about 40% stronger for By > 0 than for By < 0 in NH winter. We also discuss recent advances in the physical understanding of the By-effect. Our results highlight the importance of the IMF By-component for space weather and must be taken into account in future space weather modeling.

How to cite: Holappa, L., Asikainen, T., and Mursula, K.: Explicit IMF By-dependence in geomagnetic activity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-850, https://doi.org/10.5194/egusphere-egu21-850, 2021.

EGU21-529 | Presentations | MAL22 | Hannes Alfvén Medal Lecture 2020

Magnetospheric Response to Solar Wind Forcing: ULF Waves – Particle interaction Perspective 

Qiugang Zong

Solar wind forcing, e.g. interplanetary shock and/or solar wind dynamic pressure pulses impact on the Earth’s magnetosphere manifests many fundamental important space physics phenomena including producing electromagnetic waves, plasma heating and energetic particle acceleration. This paper summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma physic based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations.

Magnetosphere response to solar wind forcing, is not just “one-kick” scenario. It is found that after the impact of solar wind forcing on the Earth’s magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change of interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to generate series kind of waves including poloidal mode ultra-low frequency (ULF) waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region response to the impact usually contain two contributing steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by the wave-particle resonant acceleration dominated by global or localized poloidal ULF waves excited at various L-shells.

Generalized theory of drift and drift-bounce resonance with growth or decay localized ULF waves have been developed to explain in situ spacecraft observations. The wave related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. It is worthy to point out here that poloidal ULF wave is much more efficient to accelerate and modulate electrons (fundamental mode) in the radiation belt and charged ions (second harmonic) in the ring current region. The results presented in this paper can be widely used in solar wind interacting with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.

How to cite: Zong, Q.: Magnetospheric Response to Solar Wind Forcing: ULF Waves – Particle interaction Perspective , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-529, https://doi.org/10.5194/egusphere-egu21-529, 2021.

EGU21-11152 | Presentations | MAL22 | Julius Bartels Medal Lecture 2021

The magnetic flux rope structure of coronal mass ejections – 2021 Julius Bartels Medal Lecture at vEGU

Volker Bothmer

Magnetic clouds are transient solar wind flows in the interplanetary medium with smooth rotations of the magnetic field vector and low plasma beta values. The analysis of magnetic clouds identified in the data of the two Helios spacecraft between 0.3 and 1 AU showed that they can be interpreted to first order by force-free, large-scale, cylindrical magnetic flux tubes. A close correlation of their occurrences was found with disappearing filaments at the Sun. The magnetic clouds that originated from the northern solar hemisphere showed predominantly left-handed magnetic helicities and the ones from the southern hemisphere predominantly right-handed ones. They were often preceded by an interplanetary shock wave and some were found to be directly following a coronal mass ejection towards the Helios spacecraft as detected by the Solwind coronagraph on board the P78-1 satellite. With the SOHO mission unprecedented long-term observations of coronal mass ejections (CMEs) were taken with the LASCO coronagraphs, with a spatial and time resolution that allowed to investigate their internal white-light fine structure. With complementary photospheric and EUV observations from SOHO, CMEs were found to arise from pre-existing small scale loop systems, overlying regions of opposite magnetic polarities. From the characteristic pattern of their source regions in both solar hemispheres, a generic scheme was presented in which their projected white-light topology depends primarily on the orientation and position of the source region’s neutral line on the solar disk. Based on this interpretation the graduated cylindrical shell method was developed, which allowed to model the electron density distribution of CMEs as 3D flux ropes. This concept was validated through stereoscopic observations of CMEs taken by the coronagraphs of the SECCHI remote sensing suite on board the twin STEREO spacecraft. The observations further revealed that the dynamic near-Sun evolution of CMEs often leads to distortions of their flux rope structure. However, the magnetic flux rope concept of CMEs is today one of the fundamental methods in space weather forecasts. With the Parker Solar Probe we currently observe for the first time CMEs in-situ and remotely at their birthplaces in the solar corona and can further unravel their origin and evolution from the corona into the heliosphere. This lecture provides a state-of-the-art overview on the magnetic structure of CMEs and includes latest observations from the Parker Solar Probe mission.

How to cite: Bothmer, V.: The magnetic flux rope structure of coronal mass ejections – 2021 Julius Bartels Medal Lecture at vEGU, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11152, https://doi.org/10.5194/egusphere-egu21-11152, 2021.