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.

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 PM_2.5 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.

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.

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 2^nd 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.

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 21^st 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 18^th 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 17^th 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 B_y component. However, recent studies have shown that IMF B_y is an additional, independent driver of high-latitude geomagnetic activity, leading to higher (weaker) geomagnetic activity in Northern Hemisphere (NH) winter for B_y > 0 (B_y < 0). For NH summer the dependence on the B_y sign is reversed. We quantify the size of this explicit B_y-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 B_y > 0 than for B_y < 0 in NH winter. We also discuss recent advances in the physical understanding of the B_y-effect. Our results highlight the importance of the IMF B_y-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.

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.

Over the last 25 years the theory of plate tectonics and a growing set of geo-databases have been used to develop global plate models with increasing sophistication, enabled by open-source plate reconstruction software, particularly GPlates. Today’s editable open-access community models include networks of evolving plate boundaries and deforming regions, reflecting the fact that tectonic plates are not always rigid. The theory of plate tectonics was originally developed primarily based on magnetic anomaly and fracture zone data from the ocean basins. As a consequence there has been a focus on applying plate tectonics to modelling the Jurassic to present-day evolution of the Earth based on the record of preserved seafloor, or only modelling the motions of continents at earlier times. Modern plate models are addressing this shortcoming with recently developed technologies built upon the pyGPlates python library, utilising evolving plate boundary topologies to reconstruct entirely destroyed seafloor for the entire Phanerozoic. Uncertainties in these reconstructions are large and can represented with end-member scenarios. These models are paving the way for a multitude of applications aimed at better understanding Earth system evolution, connecting surface processes with the Earth’s mantle via plate tectonics. These models allow us to address questions such as: What are the causes of major perturbations in the interplay between tectonic plate motion and Earth’s deep interior? How do lithospheric deformation, mantle convection driven dynamic topography and climate change together drive regional changes in erosion and sedimentation? How are major perturbations of the plate-mantle system connected to environmental change, biological extinctions and species radiation?

How to cite: Müller, D.: Plate tectonics and Earth System Science, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9351, https://doi.org/10.5194/egusphere-egu21-9351, 2021.

The availability of magma is a key to understand mid-ocean ridge tectonics, and specifically the distribution of the two contrasted spreading modes displayed at slow and ultraslow ridges (volcanically-dominated, and detachment fault-dominated). The part of the plate divergence that is not accommodated by magma emplaced as gabbros or basaltic dikes is taken up by normal faults that exhume upper mantle rocks, in many instances all the way to the seafloor. 

Magma is, however, more than just a material that is, or is not, available to fill the gap between two diverging plates. It is the principal carrier of heat into the axial region and as such it may contribute to thin the axial lithosphere, hence diminishing the volume of new plate material formed at each increment of plate separation. Magma as a heat carrier may also, however, if emplaced in the more permeable upper lithosphere, attract and fuel vigorous hydrothermal circulation and contribute instead to overcooling the newly formed upper plate (Cochran and Buck, JGR 2001). 

Magma is also a powerful agent for strain localization in the axial region: magma and melt-crystal mushes are weak; gabbros that crystallize from these melts are weaker than peridotites because they contain abundant plagioclase; and hydrothermally-altered gabbros, and gabbro-peridotite mixtures, are weaker than serpentinites because of minerals such as chlorite and talc. As a result, detachment-dominated ridge regions that receive very little magma probably have a stronger axial lithosphere than detachment-dominated ridge regions that receive a little more magma. 

Because magma has this triple role (building material, heat carrier, and strain localization agent), and because it is highly mobile (through porosity, along permeability barriers, in fractures and dikes), it is likely that variations in magma supply to the ridge, in time and space, and variations in where this magma gets emplaced in the axial plate, cause a greater diversity of spreading modes, and of the resulting slow and ultraslow lithosphere composition and structure, than suggested by the first order dichotomy between volcanically-dominated and detachment-dominated spreading. 

In this talk I illustrate these points using results of recent studies at the Mid-Atlantic and Southwest Indian ridges.

How to cite: Cannat, M.: On magma supply and spreading modes at slow and ultraslow mid-ocean ridges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5340, https://doi.org/10.5194/egusphere-egu21-5340, 2021.

Understanding the formation of mountain belts requires integrating quantitative insights on multiple scales. While this has long been known, it is now possible to enlarge the scales of observation by exploiting global data sets, making use of data sets covering large regions, or including automated data analysis. At the same time the lower limit of observation is pushed farther, and by now structures can be routinely analyzed at the micro- or even nano-scale over large areas making use of digital imaging techniques.

In this talk I will present results from a variety of geological settings illustrating the use of large data sets for better understanding of mountain belt dynamics. To this end, I will integrate micro-structural work, numerical and analog models, and regional studies of fault geometries and their time evolution constrained by digital field techniques and low-temperature thermochronometry. A particular focus will be laid on the role of mechanical heterogeneity and strain localization through time. It is shown that in some regions geodynamic processes are responsible for local fault geometries, while in others much more local factors such as rheological contrasts of individual layers or even the changes of rheology through time plays a major role. Multiscale studies exploiting digital techniques and including the dimension of time provide an exciting avenue for state of the art and future geological studies.

How to cite: von Hagke, C.: From Structures to Mountain Belt Dynamics – a global and multidisciplinary perspective , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2490, https://doi.org/10.5194/egusphere-egu21-2490, 2021.