Presentation type:

MAL – Medal and Award Lectures

MAL1 – Alexander von Humboldt Medal Lecture by Bojie Fu

EGU2020-2798 | Orals | MAL1 | Alexander von Humboldt Medal Lecture

Coupling Human - Earth Systems for Sustainability

Bojie Fu

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


How to cite: Fu, B.: Coupling Human - Earth Systems for Sustainability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2798,, 2020.

MAL2 – Alfred Wegener Medal Lecture by Ingeborg Levin

EGU2020-1943 | Orals | MAL2 | Alfred Wegener Medal Lecture

Radiocarbon in modern Carbon Cycle research

Ingeborg Levin

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

How to cite: Levin, I.: Radiocarbon in modern Carbon Cycle research, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1943,, 2020.

MAL3 – Arthur Holmes Medal Lecture by Donald B. Dingwell

EGU2020-2053 | Orals | MAL3 | Arthur Holmes Medal Lecture

Experimental Access to Volcanic Processes

Donald B. Dingwell

Volcanism, and its underlying magmatic origins, are key elements of the Earth System. Their central role can be summed up in the convention that a planet without volcanism is classified as dead. The scientific investigation of the origins, nature and impact of volcanic eruptions is currently one of the most vibrant areas of the solid earth sciences. Observation and quantification of volcanism is greatly assisted by its very nature which includes solid earth processes at the planetary surface and whose dynamics occur on observable timescales. Thus time and location work in our favour. Working against us however is the generally highly energetic, often highly violent, explosive nature of volcanism which frequently precludes deep access to eruptive processes during their operation. Here, the investigation of eruptive processes, together with their causes and consequences, has been greatly assisted by experimental approaches.

Highlights of the experimental investigation of volcanism have included the following:

1) The geochemical diversity of magma, together with its highly variable phase state, yield a very wide range of magmatic properties which form the basis for much of the variety of volcanic expression.

2) The eruptive products of volcanism present a wide range of types of information on the nature of volcano dynamics that can be calibrated with experimental methods.

3) The fate and influence of volcanic materials in the Earth System, whose investigation is often accessible via highly novel experiments,  provide a rich palette of impacts that have likely made the presence of volcanism on Earth a defining element in the atmosphere, hydrosphere, biosphere and elsewhere.

Experimental volcanology has a rich future...  

How to cite: Dingwell, D. B.: Experimental Access to Volcanic Processes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2053,, 2020.

MAL4 – Jean Dominique Cassini Medal Lecture by Pascale Ehrenfreund

EGU2020-10885 | Orals | MAL4 | Jean Dominique Cassini Medal Lecture

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

Pascale Ehrenfreund

One of the most fascinating questions in planetary science is how life originated on Earth and whether life exists beyond Earth. Carbonaceous compounds in the gas and solid state, refractory and icy are identified by astronomical observations in our Solar System, and distant galaxies. Among them are a large number of molecules that are essential in prebiotic chemistry and used in contemporary biochemistry on Earth. Life on Earth originated approximately 3.5 billion years ago and has adapted to nearly every explored environment. What was chemical raw materials available for life to develop? Small Solar System bodies hold clues to processes that formed our Solar System and probably contributed carbonaceous molecules and volatiles during the heavy bombardment phase to the young planets. This process may have contributed to life’s origin on Earth. Space missions that investigate the composition of comets and asteroids and in particular their organic content provide major opportunities to determine the prebiotic reservoirs available to the early Earth and Mars. Recently, the Comet rendezvous mission Rosetta has monitored the evolution of comet 67P/Churyumov-Gerasimenko during its approach to the Sun and observed numerous volatiles and complex organic compound on the cometary surface and in the coma. Several asteroid sample return missions are currently operational such as JAXA’s Hayabusa-2 which was launched in 2014 and will return samples to Earth in 2020. Hayabusa-2 also carried the German-French landing module MASCOT (mobile asteroid surface scout) that provided during the 17 hours of intensive scientific exploration new insights into the structure and composition of the asteroid Ryugu.

A fleet of robotic space missions currently targets planets and moons in order to assess their habitability and to seek biosignatures of simple extraterrestrial life beyond Earth. Prime targets in the outer Solar System include moons that may harbor internal oceans such as Europa, Enceladus, and Titan. Life may have emerged during habitable periods on Mars and remains may still be preserved in the subsurface, evaporite deposits, caves or polar regions. On Mars, a combination of solar ultraviolet radiation and oxidation processes are destructive to organic material and life on and close to the surface. However, the progress and the revolutionary quality and quantity of data on “extreme life” on Earth have transformed our view of habitability. In 2020, ESA’s ExoMars program will launch the Rosalind Franklin Rover and landing platform, and drill for the first time 2m deep into the Martian subsurface. Mars is still the central object of interest for habitability studies and life detection beyond Earth, paving the way for returned samples and human exploration.

Knowledge on the evolution of organic material in space environment such as their photochemistry and preservation potential are crucial to advance life detection strategies and instrument development. This Cassini lecture will review the evolution of organic matter in space including recent observations, space missions and laboratory research and discuss the science and technology preparation necessary for robotic and human exploration efforts investigating habitability and biosignatures in our Solar System.

How to cite: Ehrenfreund, P.: Organic chemistry in space and the search for life in our Solar System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10885,, 2020.

MAL14 – Hans Oeschger Medal Lecture by Kim M. Cobb

EGU2020-22684 | Orals | MAL14 | Hans Oeschger Medal Lecture

Paleoclimate science for the 21st century: a wishlist

Kim M. Cobb

The study of past climate trends, variability, and extremes has yielded unique insights into Earth’s changing climate, yet paleoclimate science must overcome a number of key challenges to maximize its utility in a century defined by accelerating climate change. First, the paleoclimate archive itself is at grave risk, given that i) many records end in the late 20th century, and no concerted efforts exist to extend them to the present-day, and ii) many paleoclimate archives are disappearing under continued climate change and other forms of human disturbance. Second, many paleoclimate records are comprised of oxygen isotopes, yet the coordinated, multi-scale observational and modeling infrastructures required to unravel the mechanisms governing water isotope variability are as yet underdeveloped. Lastly, in part owing to the aforementioned deficiencies, paleoclimate data assimilation efforts remain fraught with large uncertainties, despite their promise in constraining many aspects of future climate impacts, including extreme events and hydrological trends and variability. Paleoclimate science for the 21st century requires deep investments in the full integration of paleoclimate data and approaches into frameworks for climate risk and hazard assessments. In that sense, paleoclimate scientists will continue to play a key role in the communication of climate change science to key stakeholders, including the general public. Their understanding of the Earth system also equips them to contribute valuable insights to teams comprised of researchers, practitioners, and  decision-makers charged with leveraging science to inform solutions, in service to society.

How to cite: Cobb, K. M.: Paleoclimate science for the 21st century: a wishlist, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22684,, 2020.

MAL15 – Henry Darcy Medal Lecture by Xavier Sánchez-Vila

EGU2020-1435 | Orals | MAL15 | Henry Darcy Medal Lecture

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

Xavier Sanchez-Vila

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

How to cite: Sanchez-Vila, X.: Porous media as a canvas for hydro-bio-geo-chemical processes: Facing the challenges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1435,, 2020.

MAL16 – Ian McHarg Medal Lecture by Paul Wessel

EGU2020-2245 | Orals | MAL16 | Ian McHarg Medal Lecture

The Generic Mapping Tools and Community-Maintained Open Source Software

Paul Wessel

The Generic Mapping Tools (GMT; is a well-known set of software for the geosciences, in particular in the marine and solid earth disciplines. GMT is used by 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, Python, and Julia, simplifying user access to large global DEM datasets, and extending our support for the Google Earth platform. However, the biggest impact delivered by the Fall 2019 release of GMT 6 will likely be “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 changes, yet very few scientists create animations as they are traditionally difficult to design. 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 simple 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 2020, Online, 4–8 May 2020, EGU2020-2245,, 2020.

MAL18 – John Dalton Medal Lecture by Amilcare Porporato

EGU2020-11883 | Orals | MAL18 | John Dalton Medal Lecture

Hydrology without Dimensions

Amilcare Porporato

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



How to cite: Porporato, A.: Hydrology without Dimensions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11883,, 2020.

MAL21 – Louis Néel Medal Lecture by Wenlu Zhu

EGU2020-11918 | Orals | MAL21 | Louis Néel Medal Lecture

Mechanisms for Pore Fluid Stabilization of Fault Propagation and Slip

Wen-lu Zhu, Tiange Xing, Takamasa Kanaya, Zachary Zega, and Melodie French

Sudden motions of fault (i.e., fault propagation and slip) cause earthquakes. Understanding the mechanics of earthquakes requires quantitative knowledge of fault propagation and slip instability, which has long been a focus of experimental rock mechanics. In a classic framework based on the elastic rebound theory, the earthquake cycle includes the interseismic period of strain accumulation and the coseismic period of sudden strain release along a tectonic fault.

Geophysical observations reveal diverse behaviorsof fault motions resulted from strain accumulation and release, from aseismic creep to slow slip events (SSEs) to regular earthquakes. Discovery of SSEs during the interseismic period provides a new means to assess the mechanical states of a seismogenic fault between earthquakes. Most seismic studies link SSEs to high pore fluid pressure. Yet, the mechanical link between slow fault slip and high pore fluid pressure is not well understood. We conduct experimental investigation to elucidate the mechanisms responsible for pore fluid stabilization of fault propagation and slip.

Our experimental results show that slip events along gouge bearing faults can transform from fast to slow with increasing pore fluid pressures while keeping the effective pressure (i.e., confining pressure minus pore fluid pressure) constant. In these experiments, a layer of fine-grained quartz gouge was placed between the saw-cut surfaces in porous sandstone samples. The saw-cut samples were subject to conventional triaxial loading under a constant effective pressure using various combinations of confining and pore fluid pressures. Different slip events, from dynamic, audible stick-slip to slow, silent  slip, with a range of slip rates and stress drops were produced along the gauge-filled saw-cut surface. These results suggest that on the same fault, varying pore fluid pressure alone could result in a range of fault slip behaviors from dynamic to creep.

Experimental data further demonstrate that under the same effective pressure, high pore fluid pressure conditions stabilize fault propagation in a wide range of intact rocks including granite, serpentine, and sandstones. In  compact rocks (initial porosity <5%) the stabilization effect can be explained by dilatant hardening. When dilatancy occurs faster than fluid diffusion along a propagating fracture, the resultant increase in effective normal stress impedes further fracture growth. In porous sandstones (initial porosity >10%), however, dilatancy hardening alone could not adequately explain the stable  post-peak fault growth observed at slow loading rates where drained conditions are achieved. Based on the quantitative microstructural analysis of the deformed samples, we propose that the stable fault growth in highly permeable sandstones manifests stable cracking due to stress corrosion. These results elucidate the important controls of pore fluid on rock strength and fault slip beyond the effective stress law. The results provide a mechanic link between the spatially correlated SSEs and high pore fluid pressure conditions.

How to cite: Zhu, W., Xing, T., Kanaya, T., Zega, Z., and French, M.: Mechanisms for Pore Fluid Stabilization of Fault Propagation and Slip, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11918,, 2020.

MAL23 – Petrus Peregrinus Medal Lecture by Rixiang Zhu

EGU2020-12194 | Orals | MAL23 | Petrus Peregrinus Medal Lecture

Early human occupation in mainland East Asia: Implication for climate change and human evolution

Rixiang Zhu

East Asia is a key area for early human migration and evolution in the Old World. During the early Pleistocene, humans began to spread out of Africa. Detailed magnetostratigraphic dating coupled with high-precision isotopic chronology of early humans in mainland East Asia, western and southeastern Asia has provided insights into our understanding of early human adaptability to a variety of environments in the eastern Old World. Before the Middle Pleistocene, early humans occupied over a broad latitudinal range, from temperate northern China (e.g., the Nihewan Basin and the Loess Plateau) to subtropical southern China (e.g., the Yuanmou Basin). Thus oldest recorded human dispersal to East Asia apparently culminated in the ability to adapt diverse environments. Around the Middle Pleistocene Climate Transition, when the climate of Earth underwent profound changes in the length and intensity of its glacial-interglacial cycles with the dominant periodicity of high-latitude climate oscillations changing from 41 kyr to 100 kyr, there is a prominent early human flourishing in the high northern latitudes of East Asia and geographic expansion from low, through middle, to high northern latitudes of the area. The improved ability to adjust to diverse environments for early humans could have benefited from the increasing variability of global, regional and local paleoclimates and paleoenvironments and from the innovation of diet, e.g., the use of animal tissues.

How to cite: Zhu, R.: Early human occupation in mainland East Asia: Implication for climate change and human evolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12194,, 2020.

MAL24 – Philippe Duchaufour Medal Lecture by Georg Guggenberger

EGU2020-19907 | Orals | MAL24 | Philippe Duchaufour Medal Lecture

Dynamic exchange and remobilization processes as controls of soil organic carbon turnover

Georg Guggenberger, Patrick Liebmann, Patrick Wordell-Dietrich, Sebastian Preußer, Fabian Kalks, Timo Leinemann, Chiara Cerli, Ellen Kandeler, Axel Don, Robert Mikutta, and Karsten Kalbitz

Dissolved organic matter (DOM) can be a major source of organic carbon (OC) stocks in mineral soils of high-leaching forest ecosystems due to its high affinity towards reactive mineral phases, thus forming mineral-associated organic matter (MAOM). However, there is considerable dispute on the quantitative role of litter-derived DOM in the formation of MAOM in deeper mineral soils. There is also lacking proof, whether DOM is transported through soil via repeated sequences of sorption, microbial processing, and remobilization as is conceptualized by the `cascade model’ of Kaiser and Kalbitz (DOI: 10.1016/j.soilbio.2012.04.002).

We investigated into these processes by a combination of monitoring dissolved organic carbon (DOC) and CO2 fluxes in a 13C field labelling experiment at subsoil observatories, field manipulation experiments, and laboratory studies to disentangle the effects of different sources and microbial turnover on the cycling of organic matter (OM) from the top mineral soil to the subsoil.

From 13C monitoring of DOM, CO2 and OM it appeared that particularly litter-derived OM leached into the soil is quickly decomposed and contributes only little to subsoil OM at a time scale of 2-3 years. The pattern of the 13C pulse in DOM and OM through the soil profile indicated a cascade-type transport of the litter-derived OM and that the MAOM formed is quite labile. The use of segmented suction plates showed that there are preferential flow paths to the subsoil that persist for years. Large DOC fluxes along these flow paths likely create hotspots where microbial processing may dominate the formation of MAOM, opposed to regions of low OM fluxes, where rather direct sorption prevails. The cascade model was also clearly supported by experiments investigating OM exchange processes of artificial mineral-organic associations exposed to field conditions. The highly OM-loaded minerals were microbial hotspots and, besides the selective retention of more strongly adsorbable DOM molecules, microbial assimilation appeared to be largely involved in the release of OM back into solution.

In conclusion, repeated sorption, microbial processing and remobilization cycles appear to control the formation of MAOM during migration of OM at long time scales. While these processes partly explain concentration, age, and composition of OM within the soil profile, horizontal variability in DOM fluxes are likely the key for different processes in the formation of MAOM.

How to cite: Guggenberger, G., Liebmann, P., Wordell-Dietrich, P., Preußer, S., Kalks, F., Leinemann, T., Cerli, C., Kandeler, E., Don, A., Mikutta, R., and Kalbitz, K.: Dynamic exchange and remobilization processes as controls of soil organic carbon turnover, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19907,, 2020.

MAL26 – Ralph Alger Bagnold Medal Lecture by Thomas J. Coulthard

EGU2020-22691 | Orals | MAL26 | Ralph Alger Bagnold Medal Lecture

Geomorphic Apophenia: Inferring meaning where there could be none?

Tom Coulthard

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

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

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


How to cite: Coulthard, T.: Geomorphic Apophenia: Inferring meaning where there could be none?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22691,, 2020.

MAL30 – Vening Meinesz Medal Lecture by Willi Freeden

EGU2020-3650 | Orals | MAL30 | Vening Meinesz Medal Lecture

Geodesy and Mathematics: Interactions in Multiscale Mollifier Regularization Methods

Willi Freeden

The lecture highlights arguments that, coming from Mathematics, have fostered the advancement of Geodesy, as well as those that, generated by geodetic problems, have contributed to the enhancement in Mathematics.

We particularly deal with novel applications to Geodesy in the context of multiscale approximation (MA). In fact, multiscale reconstruction and decorrelation methods are a research field originated in geophysics for, e.g., earthquake modeling some decades ago, in which today's Geodesy and Mathematics show mutual influences, especially on the subject of spectral and space data sampling.

We particularly focus the attention on inverse problems of Geodesy and multiscale mollifier regularization 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.

Neither extreme depth to explain all facets of the geodetic observational situation nor penetrative handling of mathematical obligations and technicalities can be expected. The lecture is just an \lq \lq appetizer'' served to enjoy the tasty meal "Mathematical Geodesy Today'' to be shared by geodesists and mathematicians.

How to cite: Freeden, W.: Geodesy and Mathematics: Interactions in Multiscale Mollifier Regularization Methods, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3650,, 2020.

MAL48 – Angela Croome Award Lecture by Elizabeth Gibney

EGU2020-22693 | Orals | MAL48 | Angela Croome Award Lecture

From black holes to Brexit: the inside track on science journalism

Elizabeth Gibney

Communication is now a fundamental part of being a scientist. Public debate and funding decisions can be shaped by which research get picked up by the media as well as how the story is told. This talk will delve into how journalists find, report and write stories and give insights into the challenges and adventures involved. It will also reflect on how researchers can best interact with the media, both to improve science communication and the reach of their work. Finally it will touch on the multiple roles that science journalists play: as entertainers, conduits for important information and critical voices that hold science to account.

How to cite: Gibney, E.: From black holes to Brexit: the inside track on science journalism, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22693,, 2020.

ITS3.1/NP1.2 – Tipping Points in the Earth System

EGU2020-9491 | Displays | ITS3.1/NP1.2 | Lewis Fry Richardson Medal Lecture

Global Stability Properties of the Climate: Melancholia States, Invariant Measures, and Phase Transitions

Valerio Lucarini

For a wide range of values of the incoming solar radiation, the Earth features at least two attracting states, which correspond to competing climates. The warm climate is analogous to the present one; the snowball climate features global glaciation and conditions that can hardly support life forms. Paleoclimatic evidences suggest that in past our planet flipped between these two states. The main physical mechanism responsible for such instability is the ice-albedo feedback. Following an idea developed by Eckhardt and co. for the investigation of multistable turbulent flows, we study the global instability giving rise to the snowball/warm multistability in the climate system by identifying the climatic Melancholia state, a saddle embedded in the boundary between the two basins of attraction of the stable climates. We then introduce random perturbations as modulations to the intensity of the incoming solar radiation. We observe noise-induced transitions between the competing basins of attractions. In the weak noise limit, large deviation laws define the invariant measure and the statistics of escape times. By empirically constructing the instantons, we show that the Melancholia states are the gateways for the noise-induced transitions in the weak-noise limit. In the region of multistability, in the zero-noise limit, the measure is supported only on one of the competing attractors. For low (high) values of the solar irradiance, the limit measure is the snowball (warm) climate. The changeover between the two regimes corresponds to a first order phase transition in the system. The framework we propose seems of general relevance for the study of complex multistable systems. Finally, we propose a new method for constructing Melancholia states from direct numerical simulations, thus bypassing the need to use the edge-tracking algorithm.


V. Lucarini, T. Bodai, Edge States in the Climate System: Exploring Global Instabilities and Critical Transitions, Nonlinearity 30, R32 (2017)

V. Lucarini, T. Bodai, Transitions across Melancholia States in a Climate Model: Reconciling the Deterministic and Stochastic Points of View, Phys. Rev. Lett. 122,158701 (2019)

How to cite: Lucarini, V.: Global Stability Properties of the Climate: Melancholia States, Invariant Measures, and Phase Transitions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9491,, 2020.

AS3.4 – Atmospheric Chemistry and Transport: Observing and Modeling the not-so-well-mixed Troposphere and the well-stratified Lower Stratosphere

EGU2020-22479 | Displays | AS3.4 | Vilhelm Bjerknes Medal Lecture

The Nonlinear Nature of Atmospheric Chemistry

Michael Prather

When scientific or policy-relevant questions involve atmospheric chemistry, one often hears "nonlinear" being invoked to describe the problem in a vague unspecific way.  The precise nature of the nonlinearity is never delineated, and we are left with the fuzzy impression that nonlinear problems are difficult to solve or have no simple answer.  For differentiable systems, nonlinear behavior can be expressed through a Taylor expansion whereby any of the 2nd order terms (x2, y2 or xy) are the first nonlinear parts.  In this lecture we shall 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; 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 embracing 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 2020, Online, 4–8 May 2020, EGU2020-22479,, 2020.

AS3.11 – Multiphase chemistry of secondary aerosol formation under severe haze

EGU2020-1319 | Displays | AS3.11 | Highlight | AS Division Outstanding ECS Lecture

Aerosol Pollution in Asia and Its Interactions with Climate

Meng Gao

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

How to cite: Gao, M.: Aerosol Pollution in Asia and Its Interactions with Climate, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1319,, 2020.

BG3.22 – Terrestrial ecosystem responses to global change: integrating experiments and models to understand carbon, nutrient, and water cycling

EGU2020-4822 | Displays | BG3.22 | Highlight | Vladimir Ivanovich Vernadsky Medal Lecture

Human induced changes on the global carbon cycle over the last 60 years

Pierre Friedlingstein

Human activities have an unprecedented impact on the global carbon cycle.  Atmospheric CO2 concentrations have been continuously monitored since 1958, and show a 30% increase, from 315 ppm in 1958 to 411 ppm in 2019. 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 the current rate of increase in fossil fuel emission of about 1% per year is lower than over the 2000s (about 3.0 % per year), there are no sign of global emissions peaking 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 mechanism 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, atmospheric CO2 would already be about 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 evidences 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 on the global carbon cycle over the last 60 years, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4822,, 2020.

BG3.24 – Soil Carbon linked to global change

EGU2020-12339 * | Displays | BG3.24 | Highlight | BG Division Outstanding ECS Lecture

The response of deep soil carbon to climate change: Empirical studies from forests to farmland and the tropics to the arctic

Caitlin Hicks Pries

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 begun to be 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 and the potential of various soil depths to generate a positive feedback to climate change is undetermined. As predictive models of terrestrial carbon storage move toward more mechanistic process representations, we need to understand how the carbon cycle differs across soil depths. We present depth-explicit measurements of soil CO2 production from seven studies, including five in situ deep soil warming experiments and two laboratory incubations. The experiments’ locations ranged from coniferous to hardwood temperate forests in the United States and from volcanic soils in Hawaii to agricultural soils in France. The incubated soils came from a former agricultural field and arctic tundra. We have found that in temperate forests, deep soil carbon is just as vulnerable to warming-induced losses as surface soils and that warming has caused a shift in the source of carbon being respired at all depths. However, where minerals are strongly associated with organic carbon, as in Hawaii, or in degraded soils where much of the organic carbon has been lost, deep soil carbon is not vulnerable to warming-induced losses. Thus, the response of deep soil to climate change seems to be dependent on how available deep soil carbon is to microbes.

How to cite: Hicks Pries, C.: The response of deep soil carbon to climate change: Empirical studies from forests to farmland and the tropics to the arctic, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12339,, 2020.

CL1.14 – Past climate reconstructions from ice core records: limits and gaps in the interpretation of proxies embedded in the ice

EGU2020-22651 | Displays | CL1.14 | Highlight | Milutin Milankovic Medal Lecture

Astronomical forcing and climate : insights from ice core records

Valérie Masson-Delmotte

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

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

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

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

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

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

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

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

How to cite: Masson-Delmotte, V.: Astronomical forcing and climate : insights from ice core records, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22651,, 2020.

CL3.2 – Predictions of climate from seasonal to (multi)decadal timescales (S2D) and their applications

EGU2020-14046 | Displays | CL3.2 | Arne Richter Award for Outstanding ECS Lecture

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

François Massonnet

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

How to cite: Massonnet, F.: Making an informed use of observations and climate models to advance understanding of past and future sea ice changes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14046,, 2020.

CR2.6 – Remote sensing of the cryosphere

EGU2020-10448 * | Displays | CR2.6 | Highlight | CR Division Outstanding ECS Lecture

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

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

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

How to cite: Hogg, A., Gourmelen, N., Rigby, R., and Slater, T.: Draining and Filling of an Interconnected Sub-glacial Lake Network in East Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10448,, 2020.

ERE4.1 – Versatile subsurface storage for future energy systems

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.: An overview about the interaction between the underground pumped storage hydropower (UPSH) and the saturated subsurface medium: effects of the water exchanges on the environment and the plant efficiency , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5531,, 2020.

G5.2 – Atmospheric and Environmental Monitoring with Space-Geodetic Techniques

EGU2020-9418 | Displays | G5.2 | Highlight | G Division Outstanding ECS Lecture

Tropospheric products as a signal of interest – overview of troposphere sensing techniques

Karina Wilgan, Witold Rohm, Jaroslaw Bosy, Alain Geiger, M. Adnan Siddique, Jens Wickert, and Galina Dick

Microwave signals passing through the troposphere are delayed by refraction. Its high variations, both in time and space, are caused mainly by water vapor. The tropospheric delay used to be considered only as a source of error that needed to be removed. Nowadays, these delays are also a source of interest, for example, tropospheric delays or integrated water vapor information are being assimilated into nowcasting or numerical weather prediction (NWP) models. Moreover, long time series of tropospheric observations have become an important source of information for climate studies. On the other hand, the meteorological data is supporting the space-geodetic community by providing models that can be used to reduce the troposphere impact on the signal propagation.

There are several ways of observing the troposphere, especially considering water vapor.  First one are the classical meteorological: in-situ measurements, radiosondes or radiometers, from which we can sense directly the amount of water vapor. Another, indirect way of observing the water vapor distribution is by using the Global Navigation Satellite Systems (GNSS). This method is called GNSS meteorology. Other microwave techniques such as Very Long Baseline Interferometry (VLBI), Interferometric Synthetic Aperture Radar (InSAR) or space-based Radio Occultations (RO) can also be used in a similar way to GNSS.

This contribution presents an overview of the troposphere sensing techniques with examples of their applications. We present a multi-comparison of the tropospheric products, i.e. refractivity, tropospheric delays in zenith and slant directions and integrated water vapor. The integration of the different data sources often leads to an improved accuracy of the tropospheric products but requires a careful preparation of data. The combination of the data sources allows for using techniques of complementary properties, for example InSAR with very high spatial resolution with GNSS observations of high temporal resolution. With the emergence of new technologies, some traditional ways of tropospheric measurements can be augmented with the new methods. For example, we have tested meteo-drones as an alternative to radiosondes. The comparisons with GNSS data shows a good agreement of the drone and microwave data, even better than with radiosondes.

How to cite: Wilgan, K., Rohm, W., Bosy, J., Geiger, A., Siddique, M. A., Wickert, J., and Dick, G.: Tropospheric products as a signal of interest – overview of troposphere sensing techniques, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9418,, 2020.

GD5.2 – Subduction zones: volatiles, dynamics, and melt

Melting at convergent plate boundaries

At divergent plate boundaries hot mantle upwelling is associated with abundant melt generation and volcanism. At convergent plate boundaries such as subduction zones and continental collision zones thick and cold plates feed mantle downwellings. Yet these "cold" regions also show abundant volcanic activity with mean volcanic output rates of almost similar order of magnitudes (White et al., 2006, G-cubed). Responsible melt generation mechanisms are addressed including a) volatile driven decrease of the solidus temperature, b) decompressional melting in the mantle wedge or in shallow asthenosphere associated with delamination, or c) increased radiogenic heating within thickened continental crust.     

Melt transport mechanisms

The above processes form partially molten regions. 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. As another magma ascent mechanism diapirism is addressed.  

Modelling magmatic systems in thickened continental crust

Once basaltic melts rise from subducting slabs, 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, and diapirism. 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 the two-phase flow crustal models with elastic dyke-propagations models (Maccaferri et al., 2019, G-cubed) are promising.      


How to cite: Schmeling, H.: Melting processes at convergent plate boundaries: from melt segregation, extraction to the formation of crustal magmatic systems , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6912,, 2020.

GD10.1 – Advances in Forward and Inverse Numerical Modelling of Geological Processes: Methods and Applications

EGU2020-7447 | Displays | GD10.1 | Highlight | GD Divison Outstanding ECS Lecture

Numerical modelling of igneous processes

Tobias Keller

Magma matters. From magmatism facilitating the differentiation of terrestrial planets into core, mantle and crust, to the magmatic activity that modulates plate tectonics and deep volatile cycles to maintain a habitable Earth, to volcanism that causes terrible hazards but also provides rich energy and mineral resources – igneous processes are integral to Earth and other planets. Our understanding of volcanoes and their deep magmatic roots derives from a range of disciplines including field geology, petrology and geochemistry, and geophysical imaging. Observational and experimental studies, however, are hampered by incomplete access to processes that play out across scales ranging from sub-micron size to thousands of kilometres, and from seconds to billions of years. Computational modelling provides tools 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 such as mineral grains, melt films, and vapour bubbles. This approach has been used successfully to model both porous flow of melt percolating through compacting partially molten rock, as well as suspension flow of crystals settling in convecting magma bodies. My recent work has introduced a new modelling framework to bridge the porous and suspension flow limits, and to extend beyound solid-liquid systems to multi-phase systems including several solid, liquid, and vapour phases. These advances provide new insights into the dynamics of crustal mush bodies, the outgassing and eruption of shallow magma reservoirs, and the generation of mineral resources by exsolution of exotic magmatic liquids.

How to cite: Keller, T.: Numerical modelling of igneous processes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7447,, 2020.

GI1.1 – Open session on geoscience instrumentation and methods

EGU2020-7426 | Displays | GI1.1 | Highlight | Christiaan Huygens Medal Lecture

Multi-length probes in GPR and TDR data

Raffaele Persico

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

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


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


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

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

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

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

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

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

How to cite: Persico, R.: Multi-length probes in GPR and TDR data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7426,, 2020.

GM1.1 – Geomorphology Frontiers: Earth Surface Dynamics in an era of extremes

EGU2020-4726 | Displays | GM1.1 | Highlight | GM Division Outstanding ECS Lecture

Sliding, flowing, rocking and rolling: Sediment and hazard cascades through mountain landscapes

Georgina Bennett

Mountain landscapes are beautiful, yet hazardous, and vulnerable to climate change and population growth. Not only is the study of these landscapes geomorphically captivating, but it is increasingly relevant to society. Three Grand Challenges in the study of processes, landscapes and hazards in mountain regions are (1) Understanding and predicting the response of earth surface processes to climate (2) Monitoring and early warning of extreme events such as landslides and floods and (3) Accounting for connectivity and feedbacks between hillslopes and channels in landscape evolution and hazards. We need a suite of tools and approaches to address these challenges. Harnessing the growing archive of satellite and aerial photography helps us to study landscape dynamics and response to drivers such as climate over large regions. Innovative sensor technology is needed to understand landscape dynamics at a finer scale and to develop real time warning of extreme events. Finally, we need conceptual models that capture the essence of landscape dynamics and help to forecast hazards as they slide, flow, rock and roll through the landscape.

How to cite: Bennett, G.: Sliding, flowing, rocking and rolling: Sediment and hazard cascades through mountain landscapes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4726,, 2020.

GMPV1.7 – Radiogenic isotopes: approaches and tools to unravel the past

EGU2020-21442 | Displays | GMPV1.7 | Highlight | Robert Wilhelm Bunsen Medal Lecture

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

Holly Stein

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

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

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

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

How to cite: Stein, H.: How Two Unassuming Elements, Re and Os, Assumed Acclaim in the Geosciences, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21442,, 2020.

HS2.5.1 – Large scale hydrology

EGU2020-6086 | Displays | HS2.5.1 | Arne Richter Award for Outstanding ECS Lecture

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

Andreas Hartmann

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

How to cite: Hartmann, A.: The karst and the furious – ways to keep calm when dealing with karst hydrology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6086,, 2020.

NH5.5 – Natural hazards and climate change impacts in coastal areas

EGU2020-2100 | Displays | NH5.5 | Highlight | Sergey Soloviev Medal Lecture

Notes from the Front Lines of the Climate Crisis - The Threat of Cyclonic Storms and Sea Level Rise in a Warming World

John Clague

The loss of life from natural hazards has decreased over the past century, due partly to much improved understanding and monitoring of hazards and partly to improvements in preparedness, communication, engineered infrastructure. This has happened at a time when human numbers have more than quadrupled and now approach 8 billion, and when populations in areas vulnerable to earthquakes and cyclones have greatly increased. Now, however, we may be on the doorstep of a ‘tipping point’ in human suffering and life loss due to the rapid changes in Earth’s climate that we are experiencing. Human-induced climate change is increasingly amplifying dangerous meteorological processes, including severe storms, drought, wildfires, heat waves, and flooding. These changes have no precedent in the past 10,000 years and are blurring the distinction between ‘natural hazards’ and human-induced hazards. The threats posed by climate change are legion; in this presentation, I discuss a set of linked phenomena that represent an emerging threat to people and society over the remainder of this century and beyond – specifically sea-level rise and coincident stronger cyclonic storms, which, on occasion, inundate low-lying coastal areas. Hurricanes and typhoons are likely to become more intense in a warmer climate and will produce higher storm surges that move ashore on an elevated sea surface. The average level of Earth’s oceans is currently rising at a rate of over 3 mm per year, which is nearly 50 percent higher than a century ago. The rate of sea-level rise is increasing due, in part, to increasing transfers of water into oceans from glaciers and ice sheets and, in part, to the warming and expansion of seawater. Scientists forecast that average global sea level will be about 1 m higher by the end of this century than today. Over 600 million people, nearly 10% of the human population, currently live less than 10 m above sea level, many in growing coastal megacities. That number will increase dramatically over the next 50 years, increasing the overall risk that people face from extreme storms. The number of people living at low elevations along coasts, and thus exposed to flooding from storm surges, is highest in Asia, particularly in China, India, Bangladesh, Indonesia, and Viet Nam, which are ill-equipped to deal with the emerging crisis. Within limits, humans can adapt to severe storms and higher sea levels, but few countries have the resources to adequately protect people and property from this threat. Thus, without urgent action on a global scale to limit the damage we are causing to Earth’s climate and without a stabilization of human numbers, many populated low-lying coastal areas could become uninhabitable by the end of this century. The forced relocation of large numbers of people is likely to cause suffering and conflict that we do not appreciate and have not planned for. More generally, human suffering stemming from human-induced climate change will outstrip the progress we have made over the past century in reducing life loss from ‘natural hazards’.

How to cite: Clague, J.: Notes from the Front Lines of the Climate Crisis - The Threat of Cyclonic Storms and Sea Level Rise in a Warming World, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2100,, 2020.

NH9.1 – Global and continental scale risk assessment for natural hazards: methods, practice and open loss and risk assessment

EGU2020-2400 | Displays | NH9.1 | NH Division Outstanding ECS Lecture

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

Vitor Silva

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

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

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

How to cite: Silva, V.: Global Seismic Risk Assessment: the Wrong, the Right, and the Truth, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2400,, 2020.

NH9.13 – Communicating Hazard and Risk: What do we know about how to make this information understandable?

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

How to cite: Horwell, C. J.: The health hazards and impacts of volcanic ash: an interdisciplinary journey towards effective mitigation, protection and communication, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8651,, 2020.

NP7.1 – Nonlinear Waves and Fracturing

EGU2020-4439 | Displays | NP7.1 | Highlight | NP Division Outstanding ECS Lecture

Soliton turbulence in weakly nonlinear and weakly dispersive media

Ekaterina Didenkulova

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

Firstly, pair soliton collisions have been analyzed as an elementary act of the soliton turbulence for further understanding of their impact on multi-soliton dynamics. Different types of solitons have been considered: “thick” or “top-table” solitons, algebraic solitons, solitons of different polarities. From the point of view of the turbulence theory, the interactions of waves (particles) should be described by the statistical moments of the wave field. These moments, with the exception of the first two, are not invariants of the equation and are not preserved within the time. 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 fields’ 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 waves’ (so-called “freak/rogue waves”) occurrence.

The reported study was funded by RFBR according to the research projects 19-35-60022 and 18-02-00042.

How to cite: Didenkulova, E.: Soliton turbulence in weakly nonlinear and weakly dispersive media, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4439,, 2020.

OS1.0 – The North Atlantic: natural variability and global change

EGU2020-4832 | Displays | OS1.0 | Highlight | Fridtjof Nansen Medal Lecture

The North Atlantic Oscillation and related topics

Richard Greatbatch

We start with the severe European winter of 1962/63, a winter when the North Atlantic Oscillation (NAO) index was strongly negative with persistent easterly wind anomalies across northern Europe and the British Isles. We then note that the NAO is a manifestation of synoptic Rossby wave breaking. The positive feedback with which synoptic eddies act to maintain the atmospheric jet stream against friction turns out to also be the mechanism by which the equatorial deep jets in the ocean are maintained against dissipation. We were fortunate to be able to demonstrate this in both a simple model set-up that supports deep jets and directly from mooring data on, and on either side of, the equator at 23 W 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 brief 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.  The models we use for prediction not only contain surprisingly large biases but also require the parameterization of unresolved processes and some brief discussion will be given on the representation of mesoscale eddies in ocean models, such as are used in prediction systems and for making future climate projections.



How to cite: Greatbatch, R.: The North Atlantic Oscillation and related topics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4832,, 2020.

OS3.8 – Exploring marine biogeochemical cycles: organic matter and pollutants

EGU2020-10736 | Displays | OS3.8 | Highlight | OS Division Outstanding ECS Lecture

Controls over the export flux of marine snow into the deep ocean

Frederic Le Moigne

The oceanic biological carbon pump (BCP) regulates the Earth carbon cycle by transporting part of the photosynthetically fixed CO2 into the deep ocean. Suppressing this mechanism would result in an important increase of atmospheric CO2 level. The BCP occurs mainly in the form of organic carbon particles (POC) sinking out the surface ocean. Various types of particles are produced in surface ocean. They all differ in production, sinking and decomposition rates, vertically and horizontally. The amount of POC transported to depths via these various export pathways as well as their decomposition pathways all have different ecological origins and therefore may response differently to climate change. Here I will briefly review some of the processes driving both particle export out of the euphotic zone (0-100m) as well as particles transport within the mesopelagic zone (100-1000m). In the early 2000s, strong correlations between POC and mineral (calcite an opal) fluxes observed in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. These relationships were first considered as being universal. However global analysis of POC and mineral ballast fluxes showed that mineral ballasting is important in regions like the high-latitude North Atlantic but that in most places (some of which efficiently exporting) the unballasted fraction often dominates the export flux. In such regions, we later on showed that zooplankton-mediated export (presence of faecal pellets) and surface microbial abundance were important drivers of the efficiency of particles export. Similar trends were found globally by including bacteria and zooplankton abundances to a global reanalysis of the global variations of the POC export efficiency. This implies that the whole ecosystem structure, rather than just the phytoplankton community, is important in setting the strength of the biological carbon pump. Further down in the water column (mesopelagic zone), processes impacting the transport of particles are less clear. Sinking particles experience a number of biotic and abiotic transformations during their descent. These includes solubilization, remineralisation, fragmentation, ingestion/active transport, break down among others. While some potential factors such as O2 concentration and temperature have been proposed as powerful controls, globally evidences are often inconsistent. Current challenges related to the role of particles consumption by zooplankton and fishes as well as the role of particles attached prokaryotes (bacteria and archaea) in setting the efficiency of the carbon transport in the mesopelagic zone will be discussed.

How to cite: Le Moigne, F.: Controls over the export flux of marine snow into the deep ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10736,, 2020.

PS1.4 – Planetary Space Weather

EGU2020-7422 | Displays | PS1.4 | Arne Richter Award for Outstanding ECS Lecture

Space Weather effects on Mars’ ionosphere: From our current knowledge to the way forward

Beatriz Sánchez-Cano

Planetary Space Weather is an emerging topic of increasing interest. Forecast this planetary space weather, however, is currently very challenging mainly due to the lack of continuous solar wind observations for each planet. In the particular case of Mars, understanding the ionospheric behaviour following Space Weather activity is essential in order to assess the response of the Martian plasma environment to the dissipation of energy from solar storms. Moreover, it gives information on the effects on the current technology deployed on the red planet. Despite the recent considerable exploration, however, there is still no continuous upstream solar wind observations at Mars. This fact makes the analysis of the different Martian plasma datasets challenging, relying on solar wind models and upstream solar wind observations at 1 AU (e.g. at Earth’s L1 point, STEREO, etc.) when Mars and those satellites are in apparent opposition or perfectly aligned in the Parker spiral.

This lecture will focus on our current knowledge of the Martian ionosphere, which is the layer that links the neutral atmosphere with space, and acts as the main obstacle to the solar wind. In particular, I will focus on our recent advances in the understanding of the Martian ionospheric reaction to different Space Weather events during the solar cycle, both from the data analysis and ionospheric modelling perspectives. Some important aspects to consider are the bow shock, magnetic pileup boundary, and ionopause characterization, as well as the behaviour of the topside and bottomside of the ionosphere taking into account the planet’s orbital eccentricity. Moreover, I will show the effect of electron precipitation from large Space Weather events in the very low Martian ionosphere, a region that it is non-accessible to in-situ spacecraft observations. Finally, I will conclude the presentation by giving my perspective on some of the key outstanding questions that remain unknown, and I consider they constitute the next generation of Mars’ ionospheric and Space Weather science and exploration.

How to cite: Sánchez-Cano, B.: Space Weather effects on Mars’ ionosphere: From our current knowledge to the way forward, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7422,, 2020.

PS5.2 – Jupiter and Saturn: Results from Juno and Cassini

EGU2020-3441 | Displays | PS5.2 | David Bates Medal Lecture

From storms to planetary-scale disturbances in the atmospheres of Jupiter and Saturn

Agustín Snchez-Lavega

SM1.1 – General Contributions on Earthquakes, Earth Structure, Seismology

EGU2020-12702 | Displays | SM1.1 | Highlight | Arne Richter Award for Outstanding ECS Lecture

Environmental seismology: Listening to landslides whispering

Wei-An Chao

The rapidly emerging field of Environmental Seismology (EnviroSeis) uses seismological techniques to monitor geomorphic processes at Earth’s surface, providing non-invasive, relatively inexpensive, continuous constraints on physical properties and dynamics of surface processes including landslides, debris flows, snow avalanches, river sediment transport, and variations in groundwater table. EnviroSeis has direct ties to real-time geohazards monitoring and provides timely warnings for the hazard mitigation and assessment. Nowadays, the places in world with real-time seismic networks are ready to implement EnviroSeis. The major topic focused on here is how to provide relevant information on the deep-seated landslides associated to the three-time stages:

  • Pre-slide: (1) seismic precursor and (2) seismic velocity changes corresponding to basal sliding behavior.
  • Sliding: A real-time landquake monitoring (RLMS;
  • After-slide: (1) near-real-time monitoring of river sediment transport and (2) early warning of the landslide-generated tsunami.

How to cite: Chao, W.-A.: Environmental seismology: Listening to landslides whispering, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12702,, 2020.

SSP2.2 – Integrated Stratigraphy - Recent advances in stratigraphic systems and geochronology

EGU2020-16771 | Displays | SSP2.2 | Highlight | SSP Division Outstanding ECS Lecture

Constraints on late Miocene ice volume variability from a global benthic δ18O compilation (8.0-5.0 Ma)

Anna Joy Drury, Thomas Westerhold, David Hodell, Sarah White, Ana Christina Ravelo, and Roy Wilkens

Accurate stable isotope stratigraphies are essential for understanding how past climates are influenced by orbital forcing. Deep-sea benthic foraminiferal δ18O and δ13C stratigraphies can provide precise astronomical age control and record changes in past deep-sea ocean temperatures, global ice volume and the carbon cycle. Our understanding of Plio-Pleistocene climate dynamics has improved through the development of global (LR04; Lisiecki & Raymo, 2005) and regional stacks (Ceara Rise; Wilkens et al., 2017). However, the late Miocene climate system remains poorly understood, in part because the late Miocene benthic foraminiferal δ18O stratigraphy is notoriously low amplitude.

Here, we present the first global late Miocene global benthic foraminiferal δ18O compilation spanning 8.00-5.33 Ma. We formed a “Base Stack” using six continuous benthic stratigraphies from the Atlantic (ODP Sites 982 (N), 926 (E) and 1264 (S)) and Pacific Oceans (IODP Sites U1337 and U1338 (E), ODP Site 1146 (W)). To avoid misidentification of individual excursions between sites, we verified existing splices, generated isotope data where necessary and established independent astrochronologies. To accompany the “Base Stack”, we compiled a “Comprehensive Stack”, which incorporates single-hole benthic δ18O stratigraphies to optimise global coverage.

The new global late Miocene benthic foraminiferal δ18O stack represents a stratigraphic reference section back to 8.00 Ma. The stack is accurately tied to the Geomagnetic Polarity Time Scale between Chrons C3r and C4n.2n using the magnetostratigraphy from IODP Site U1337. We recognise 68 new δ18O Marine Isotope Stages (MIS) between 7.7 and 6.5 Ma. An exceptional global response is imprinted on the dispersed sites between 7.7-6.9 & 6.4-5.4 Ma, when a strong 40 kyr heartbeat dominates the climate system. The origin of these cycles remains unclear. The influence of deep-sea temperature on the benthic δ18O stack is explored at IODP Site U1337 using Mg/Ca data. The dominant 40-kyr δ18O cycles are asymmetric, suggesting at least a partial ice volume imprint and raising the possibility that these cycles relate to early signs of northern hemisphere glaciation.

How to cite: Drury, A. J., Westerhold, T., Hodell, D., White, S., Ravelo, A. C., and Wilkens, R.: Constraints on late Miocene ice volume variability from a global benthic δ18O compilation (8.0-5.0 Ma), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16771,, 2020.

SSP4.3 – Palaeontology, Palaeoecology and Evolution of Life

EGU2020-1318 | Displays | SSP4.3 | Jean Baptiste Lamarck Medal Lecture

The early origin of feathers

Michael Benton

Feathers are a diagnostic character of birds, and yet new fossils show they likely originated more than 100 million years before the first birds. In fact, feathers probably occurred in all dinosaur groups, and in their cousins, the pterosaurs, as we showed in 2019. This finding confirms current knowledge of the genomic regulation of feather development. Our work stems from ten years of collaboration with Chinese colleagues, during which we set ourselves the taks 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.

How to cite: Benton, M.: The early origin of feathers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1318,, 2020.

SSS8.12 – Biogeochemical element cycling and mineral weathering in soils

EGU2020-3445 | Displays | SSS8.12 | Highlight | SSS Division Outstanding ECS Lecture

Soil resource dynamics in a changing world

Sebastian Doetterl

Good time for soil scientists, bad time for soils? Join me at my Soil System Sciences - OECS award lecture where I will highlight how Global Change affects soils across ecosystems and what this means for future plant-soil inter­actions and biogeochemical cycles in a warming, crowded world out of balance.

Global Change from the Arctic to the Tropics has accelerated drastically in recent decades, subsequently effecting ecosystems everywhere. Soils and biogeochemical cycling within are no exception. For example, how carbon and nutrients are stabilized in and released from soil is highly affected by changing land use and climate. Despite these changes, soil in earth system models is not represented mechanistically, but rather given a mostly budgetary “black box” function. No methodological framework is available that accounts for the combined effects of climate, geochemistry and disturbance on soil dynamics at larger scales. In addition, most of our process understanding of biogeochemical cycling in soils is derived from data-rich temperate regions. This data has limited applicability in low latitudinal (tropics) or high latitudinal (boreal/subpolar) climate zones, where soils have different properties and drastically different developmental histories.

In my talk I will illustrate with a few examples how the gaps in our understanding of soil processes across climate zones and dismissing lateral soil fluxes leads to large uncertainties in predicting future trajectories of the global carbon cycle. I will highlight how the interactions of weathering and disturbance can influence and dominate biogeochemical cycles and microbial processes in soils. I will also discuss some directions where geochemical proxies that are available at the global scale can be useful to model the spatial and temporal patterns of soil carbon storage and turnover.

How to cite: Doetterl, S.: Soil resource dynamics in a changing world, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3445,, 2020.

ST1.1 – Open Session on the Sun and Heliosphere

EGU2020-2069 | Displays | ST1.1 | Hannes Alfvén Medal Lecture

Magnetospheric Response to Solar Wind Forcing -ULF Wave - Particle interaction Perspective

Qiugang Zong

Sudden changes in solar wind forcing, e.g., those associated with interplanetary shocks and/or solar wind dynamic pressure pulses, can cause many fundamentally important phenomena in the Earth’s magnetosphere including electromagnetic wave generation, plasma heating and energetic particle acceleration. This presentation summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations. 

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

Generalized theory of drift and drift-bounce resonance with growing or decaying ULF waves  (globally distributed or localized)  has been developed to explain in situ spacecraft observations. The new wave-related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. The results showed in this presentation can be widely used in the interaction of the solar wind with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.

How to cite: Zong, Q.: Magnetospheric Response to Solar Wind Forcing -ULF Wave - Particle interaction Perspective , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2069,, 2020.

ST4.3 – Space Weather and its Effects on Terrestrial and Geo-Space Environments: Science and Application

EGU2020-3367 | Displays | ST4.3 | ST Division Outstanding ECS Lecture

Explicit IMF By-dependence in geomagnetic activity

Lauri Holappa, Timo Asikainen, and Kalevi Mursula

The interaction of the solar wind with the Earth’s magnetic field produces geomagnetic activity, which is critically dependent on the orientation of the interplanetary magnetic field (IMF). Most solar wind coupling functions quantify this dependence on the IMF orientation with the so-called IMF clock angle in a way, which is symmetric with respect to the sign of the By component. However, recent studies have shown that IMF By is an additional, independent driver of high-latitude geomagnetic activity, leading to higher (weaker) geomagnetic activity in Northern Hemisphere (NH) winter for By > 0 (By < 0). For NH summer the dependence on the By sign is reversed. We quantify the size of this explicit By-effect with respect to the solar wind coupling function, both for northern and southern high-latitude geomagnetic activity. We show that for a given value of solar wind coupling function, geomagnetic activity is about 40% stronger for By > 0 than for By < 0 in NH winter. The physical mechanism of the By-effect is not yet fully understood. Here we show that IMF By modulates the flux of energetic electrons precipitating into the ionosphere which likely modulates the ionospheric conductivity and, thus, geomagnetic activity. Our results highlight the importance of the IMF By-component for space weather and must be taken into account in future space weather modeling.

How to cite: Holappa, L., Asikainen, T., and Mursula, K.: Explicit IMF By-dependence in geomagnetic activity, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3367,, 2020.

TS3.5 – Faults and fractures in rocks : mechanics, occurrence, dating, stress history and fluid flow

EGU2020-4688 | Displays | TS3.5 | Highlight | TS Division Outstanding ECS Lecture

From Faults and Fluids to Mountain Belt Dynamics

Christoph von Hagke

For understanding the formation of mountain belts it is necessary to gain quantitative insights on fault and fracture mechanics on multiple scales. In particular, for addressing the role of fluids on larger processes, it is inevitable to constrain fault and fracture geometries at depth, as well as gain insights on how fluids influence fault mechanics. At least partly, the future of such analyses lies in exploiting large data sets, as well as in multi- and interdisciplinary research.

In this talk I will present results from variety of geological settings, including dilatant faults at Mid-Ocean Ridges, the Oman Mountains, the Khao Kwang fold-trust belt in Thailand, and the European Alps. I will show how multi-scale studies and the use of large data sets helps constraining fluid migration in mountain belts, fault geometries, as well as possible feedbacks between fluid flow and strain localization. Results are then applied to discuss the role of mechanical stratigraphy on structural style in foreland fold-thrust belts.

How to cite: von Hagke, C.: From Faults and Fluids to Mountain Belt Dynamics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4688,, 2020.

TS6.4 – Rift to ridge: the record of continental breakup processes

EGU2020-2658 | Displays | TS6.4 | Highlight | Stephan Mueller Medal Lecture

On spreading modes and magma supply at slow and ultraslow mid-ocean ridges

Mathilde Cannat


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 spreading modes and magma supply at slow and ultraslow mid-ocean ridges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2658,, 2020.

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