EGU General Assembly 2022  

There is serious concern that the hazard, or probability, of river floods is increasing over time. Anticipating any change in flood hazard is extremely important for adapting flood management strategies and thereby reducing potential damage and loss of life. However, floods are the result of complex interactions of runoff generation processes within the catchment area not easy to quantify. This presentation will review recent advances in understanding how and why river floods, and their probabilities, are changing over time.

Land use change, such as deforestation, urbanisation and soil compaction resulting from more intense agriculture, modify river floods by altering the infiltration capacity and soil moisture. Locally, these processes are well understood but less so at the catchment scale. The effect of land use on floods is particularly pronounced for flash floods in small catchments because of the role of soil permeability in infiltration at this scale. For regional floods, and for the most extreme events, land use is usually not the most important control, because areas of soil saturation are more relevant in runoff generation, which are less driven by soil permeability.

Instead, hydraulic engineering works, such as river training, reservoirs and levees, are more relevant. The effect of individual hydraulic structures can be captured well by hydraulic  modelling based on mass and momentum balance, and their role depends on the event magnitude. There is a tendency for all of these engineering works to exert the greatest effect on floods for events of intermediate magnitude, e.g. associated with return periods of the order of ten to one hundred years. Regional effects of engineering works are an active research topic.

Climate change can affect river floods at all catchment scales, from a few hectares to hundreds of thousands of square kilometres. Observed changes in river floods, e.g. in Europe, suggest that climate change is indeed modifying the river flood hazard, but the changes are not necessarily directly linked to precipitation, nor are they directly linked to rising air temperatures. The key to understanding climate change effects on floods is therefore the seasonal interaction between soil moisture (influenced by precipitation and evaporation), snow processes, extreme precipitation and runoff generation. In Europe, there have been a number of flood-rich periods in the past 500 yrs and we are currently in one of them. A trend of storm tracks to move further north in Europe has increased both average and extreme precipitation and thus river flood hazard in the Northwest of Europe, but floods are decreasing where snowmelt is relevant due to shallower snowpacks. There is a tendency for climate change to have the greatest effect on floods of large event magnitudes.

It is concluded that substantial progress has been made in recent years in understanding the role of land use, river works and climate in changing river flood hazards, both through data based and modelling approaches. Considering all three controls of change is essential in reliable flood risk assessment and management in order to maximise protection levels at an affordable cost.

Publications: https://hydro.tuwien.ac.at/forschung/publikationen/download-journal-publications/

How to cite: Blöschl, G.: Understanding changing river flood hazards, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1892, https://doi.org/10.5194/egusphere-egu22-1892, 2022.

Over recent years, research on compound weather and climate event has emerged as a new research frontier at the interface of climate science, climate impact research, engineering and statistics. Compound weather and climate events refer to the combination of multiple drivers and/or hazards that contribute to environmental or societal risk. Compound event analysis combines traditional research on climate extremes with impact-focused bottom-up assessments, thereby providing new insights on present-day and future climate risk. In this talk, I will illustrate my own trajectory into compound event analysis and highlight current and future challenges in this novel and exciting field of research. 

How to cite: Zscheischler, J.: The emergence of compound event analysis as a new research frontier, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7784, https://doi.org/10.5194/egusphere-egu22-7784, 2022.

Ion dynamics are controlled by the energy-dependent source, transport, energization, and loss processes. Systematic changes in the ion dynamics are essential to understand the ring current variations in the inner magnetosphere. The Van Allen Probes mission, which orbits near the equatorial plane inside the geosynchronous orbit, has a wide energy coverage with high energy resolution and state-of-the-art ion composition instrumentation. It provides a great opportunity to investigate plasma dynamics. In this talk, I will present some of our recent studies on the ion dynamics of different populations and species as well as the related plasma wave activity during geomagnetic quiet and active times.

How to cite: Yue, C.: Ion dynamics in the inner magnetosphere during Van Allen Probe Era, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-901, https://doi.org/10.5194/egusphere-egu22-901, 2022.

Every science journalist's journey into the field is unique, with no two origin stories the same. No two have precisely the same beat, writing style, or advice to hand out to those wondering how to take a shot at it themselves. Consequently, there is plenty to talk about to those curious about the field. But something I've noticed that is absent from most journalism lectures or talks is a sense of just how exhilarating it can be, particularly as someone who transitioned from academia into journalism with zero experience in the latter. Like every job, it has its pros and cons—but telling stories about worlds near and far, and the volcanic fires that fleck their surfaces, is as near to an ideal career as I can imagine. I hope that, with this talk, I can convince others to take that same leap I did, try something different, and experience that idiosyncratic thrill for themselves.

How to cite: Andrews, R.: Fire and Ink: The Joy of Volcanic Storytelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1123, https://doi.org/10.5194/egusphere-egu22-1123, 2022.

The physical cause, or origin, or generation of plate tectonics, especially how it arises from a convecting mantle on Earth (and not apparently on our solar system's other terrestrial planets) is one of the big questions in geophysics, and has  haunted (or taunted) the author  for the last 30+ years.  Although he's tried to drive the question to basic physical causes for plate boundary formation in a cold stiff lithosphere,  he's certainly taken his share of wrong turns.  His earliest attempts to understand these processes from fluid lab experiments (while a postdoc at WHOI) only achieved (1) making gallons of fluids that look much like mucus, and (2) proof that he was a lousy experimentalist.  But in the intervening decades, he's burrowed deeper into smaller and smaller scales to understand how microscale physics of mineral grains influence plate boundary formation at large scales.  This led to the most recent theory of grain damage that allows for formation of weak boundaries, corresponds to field and laboratory observations of mylonitic behavior, and has applications from the onset of early plate tectonics, to passive margin collapse, to slab segmentation and necking.   The most recent theory incorporates how mineral phases (olivine and pyroxene) mix with each other at the grain scale, and this has allowed a close comparison to new rock deformation experiments on grain mixing and shear localization, which opens up many new questions and predictions for more experiments and observations.  

How to cite: Bercovici, D.: Searching for the origin of plate tectonics, leaving no grain unturned, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9705, https://doi.org/10.5194/egusphere-egu22-9705, 2022.

Beno Gutenberg made fundamental contributions to knowledge about large-scale earth structures and properties of moderate to large earthquakes using the seismic data available at the time. Data recorded in the last few decades by improved regional networks and dense seismic arrays provide opportunities for resolving fine details of subsurface rocks and seismicity in 4D. I review such results based primarily on recent data from Southern California. The discussed topics include multi-scale seismic imaging of the crust and fault zones, monitoring temporal changes of seismic velocities, and tracking localization of rock damage and low magnitude seismicity before large earthquakes.

The seismic imaging results reveal hierarchical rock damage structures around large fault zones with intense core damage zones and bimaterial interfaces. The fault damage zones follow overall a flower-shape structure, with significant damage in the top few km that decreases in amplitude and width with depth, and they tend to be offset from the surface trace to the side with higher seismic velocity at depth. The top 100-300 m section has generally extreme seismic properties (very low Vp, Vs, Q values; very high Vp/Vs ratios), which make it highly susceptible to failure and temporal changes. Large earthquakes produce changes of seismic velocities that decay with distance from the rupture zones, but remain significant on a regional scale in the shallow crust. The co-seismic velocity changes are followed by log(t) recovery, and can be very large (e.g. >30%) in the top 100-300 m. Appreciable changes of shallow materials are also generated by atmospheric and other non-tectonic loadings on various timescales.

The results on localization processes are based on (i) estimated production of rock damage by background seismicity, (ii) spatial localization of background events within damaged areas, and (iii) progressive coalescence of individual earthquakes into clusters. The analyses reveal generation of earthquake-induced rock damage on a decadal timescale around eventual rupture zones of large earthquakes, and progressive localization of background seismicity 2-3 yrs before M > 7 earthquakes in Southern and Baja California and M > 7.5 events in Alaska. This localization phase is followed by coalescence of earthquakes into growing clusters that precede the mainshocks. Corresponding analyses around the 2004 M6 Parkfield earthquake in the creeping section of the San Andreas fault, which is essentially always localized, show opposite tendencies to those involving faults that are locked in the interseismic periods.

Continuing efforts in these topics include merging local high-resolution imaging results within regional models, monitoring temporal changes of properties at seismogenic depth, and including geodetic data and insights from laboratory experiments in the localization analyses.

How to cite: Ben-Zion, Y.: Space-time variations of crustal, fault zone, and seismicity structures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2052, https://doi.org/10.5194/egusphere-egu22-2052, 2022.

Australia is an old stable continent with a rich geological history. Limitations in sub-surface seismic imaging below the Moho, however, mean that is unclear to what extent, and to what depth, this rich geological history is expressed in the mantle. Studies of seismic anisotropy, which reflect past/present mantle deformation, can offer potential insights. One commonly employed technique is shear wave splitting, in which the wave polarisation is measured. New such results from seismic arrays deployed across central Australia, reveal a pattern of anisotropy that is consistent with past deformation of the Australian lithosphere that has been preserved for over 300 million years. Another informative technique is to use scattered surface waves, called Quasi-Love waves, that can detect lateral gradients in seismic anisotropy. The first such study for the region finds that scatterers are preferentially located near (1) the passive continental margins, and (2) the boundaries of major geological provinces within Australia. Such lateral anisotropic gradients within the continental interior imply pervasive fossilized lithospheric anisotropy, on a scale that mirrors the crustal geology at the surface. Beneath the continental margins, lateral anisotropic gradients may indicate small-scale dynamic processes in the asthenosphere, such as edge-drive convection, that are tied to the margins.

How to cite: Eakin, C.: The Deep Roots of Geology: Tectonic History of Australia as expressed by Mantle Anisotropy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2108, https://doi.org/10.5194/egusphere-egu22-2108, 2022.

I will review the main magnetosphere-ionosphere (MI) coupling mechanisms thought to play a role at Jupiter and at Saturn. We are interested in the extent to which the magnetospheres are driven by internal processes (plasma sources, planetary rotation) versus external mechanisms (solar wind, interplanetary magnetic field). At both planets, momentum is mostly transferred via the rotating planetary magnetic field from the ionosphere to the magnetosphere. The solar wind can also play a role in driving dynamics, e.g. via the interaction of corotating interaction regions (CIRs). The NASA/ESA Cassini Huygens mission revealed that Saturn’s system also has a unique feature driven by the ionosphere known as “planetary period oscillations”. These phenomena interact with the effects of the solar wind to produce complex MI coupling signatures. The NASA Juno mission has provided the first in situ evidence of MI coupling in Jupiter's polar magnetosphere. I will compare the similarities and differences between observation and theory discovered thus far.

How to cite: Bunce, E.: Magnetosphere-Ionosphere Coupling and Aurora at Jupiter and Saturn, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11375, https://doi.org/10.5194/egusphere-egu22-11375, 2022.

A long-standing question within Saturn’s magnetosphere is the source of the ubiquitous oscillations, known as planetary period oscillations (PPOs). From radio and magnetometer data it is known there are two such oscillation systems, one in the northern hemisphere and the other in the southern. In this talk, we will review analyses of azimuthal magnetic field data from the Cassini mission right up to its end in 2017 which show the presence of field-aligned currents. Using these data, several field-aligned current systems are shown to be present in Saturn’s auroral regions and their relationship with the PPOs was revealed. The implications of these results on Saturn’s periodicities, aurora, and coupling between the ionosphere and magnetosphere will be discussed.  

How to cite: Hunt, G.: Saturn's field-aligned current systems as observed by the Cassini mission, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13335, https://doi.org/10.5194/egusphere-egu22-13335, 2022.

Based on new observations and on improved ocean and climate modeling, the last decade was marked by a seminal progress in our understanding of the North Atlantic circulation.  The presentation will summarize recent insights and discuss future challenges. Based on new observations and on improved ocean and climate modeling, the last decade was marked by a seminal progress in our understanding of the North Atlantic circulation.  The presentation will summarize recent insights and discuss future challenges. Based on new observations and on improved ocean and climate modeling, the last decade was marked by a seminal progress in our understanding of the North Atlantic circulation.  The presentation will summarize recent insights and discuss future challenges.  

How to cite: Rhein, M.: On the North Atlantic Circulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1488, https://doi.org/10.5194/egusphere-egu22-1488, 2022.

Deep water masses are the driver of the global ocean circulation, critical for transporting oxygen and nutrients throughout the water column, and a crucial mitigator of current climate change. They are also notoriously hard to observe: they form in winter in ice-infested areas, and then travel around the globe too deep for most autonomous instruments to monitor them. Therefore, although they represent at least half of the ocean volume, we still know very little about their circulation and variability.

What we do know is that they are already changing, much faster than expected.

From a ship in the Southern Ocean to models in the Arctic, I will share with you my obsession for these fascinating deep waters; highlight the blind spots that remain; and describe recent and upcoming deep-water-targeting projects that get me excited.

How to cite: Heuzé, C.: Global deep waters: what we know, what we know we do not know, and what we should do about it, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1695, https://doi.org/10.5194/egusphere-egu22-1695, 2022.

The supersonic solar wind and its embedded magnetic field continuously flow outward in all directions from the sun. This magnetized plasma inflates a bubble – the heliosphere – in the very-local interstellar medium (VLISM). The Interstellar Boundary Explorer (IBEX) mission launched in late 2008 and has been continuously returning 3-D global images of Energetic Neutral Atoms (ENAs) that derive from ion populations in the heliosheath and beyond. Now spanning more than a full solar cycle, IBEX’s all-sky maps and observations uniquely inform the global outer heliosphere and its evolving interstellar interaction. Insights from IBEX, in concert with in situ observations by the two Voyager spacecraft, which were transiting two different trajectories through the outer boundaries of the heliosphere contemporaneously with IBEX, have led to a true scientific revolution in our understanding of the outer heliosphere and its interstellar interaction. This Hannes Alfvén Medal Lecture will summarize some of the many discoveries and “firsts” from the IBEX mission and their implications for the outer heliosphere and VLISM. Finally, we will also look forward to the promise of the even more advanced Interstellar Mapping and Acceleration Probe (IMAP) mission, which is under development and slated to launch in 2025.

How to cite: McComas, D.: Our Heliosphere and its Interstellar Interaction: A Solar Cycle of Global Observations and Discoveries, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1115, https://doi.org/10.5194/egusphere-egu22-1115, 2022.

Rudolf Wolf, first director of the Zürich Observatory around mid-19th century, recovered a large number of sunspot observations made by astronomers several solar cycles back. Based on that database, he defined the relative sunspot number from the number of sunspot groups and individual sunspots. He extended his daily and monthly series until 1749, whereas his yearly series to 1700 (Clette et al. 2014). Nowadays, the World Data Center Sunspot Index and Long-term Solar Observations is the responsible to maintain this sunspot number index. At the end of the 20th century, Hoyt and Schatten (1998) compiled more sunspot observations made by astronomers since the beginning of the 17th century. Thus, they created the group sunspot number index from the number of sunspot groups. Unlike the relative sunspot number, their series starts in 1610.

More recently, several works have detected some problems both in these two indices and the databases. For example, Vaquero et al. (2016) published a revised collection of sunspot group numbers correcting some of the mistakes found in the Hoyt and Schatten database, in addition to incorporate other unknown sunspot records. Currently, there is an ongoing global effort to improve the weakness of the database and recalibrate the indices. Some remarkable improvements to be carried out in future versions of the sunspot number databases have been made regarding the earliest sunspot observations recorded by astronomers such as Galileo and Scheiner, inter alia. Then, corrections of significant mistakes detected in the sunspot counting assigned to these observers in the existing databases are proposed as well as the incorporation of telescopic sunspot records made by the earliest observers not included in these databases.

The sunspot number series is the index including the longest direct solar observation set to study the long-term solar activity evolution and its influence on the Earth. Therefore, we need that the databases, in which these indices are based, are free of problematic observations and, moreover, to improve their observational coverage before mid-19th century. Thus, we will understand better past, present and future solar activity.

References

Clette, F., Svalgaard, L., Vaquero, J.M., Cliver, E.W.: 2014, Revisiting the Sunspot Number. A 400-Year Perspective on the Solar Cycle, SSRv 186, 35. DOI: 10.1007/s11214-014-0074-2.

Hoyt, D.V., Schatten, K.H.: 1998, Group sunspot numbers: a new solar activity reconstruction. Solar Phys. 179, 189. DOI: 10.1023/A:1005007527816.

Vaquero, J.M., Svalgaard, L., Carrasco, V.M.S., Clette, F., Lefèvre, L., Gallego, M.C., Arlt, R., Aparicio, A.J.P., Richard, J.-G., Howe, R.: 2016, A Revised Collection of Sunspot Group Numbers, Sol. Phys. 291, 3061. DOI: 10.1007/s11207-016-0982-2.

How to cite: Carrasco, V.: A Revised Collection of Sunspot Group Numbers: Context and Future Improvements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8388, https://doi.org/10.5194/egusphere-egu22-8388, 2022.

Many sectors of society are vulnerable to decadal changes in climate, which impact food security, freshwater availability, spread of pests and diseases, heat waves, droughts, floods, cyclones, wildfires, energy supply and demand, transport, migration, and conflict. On decadal timescales climate is influenced by both internal variability and changes in radiative forcing. Climate predictions that are initialised with observations are needed to account for all of these factors and will be reviewed in this talk.

Understanding the drivers of decadal climate is crucial for gaining confidence in forecasts. One hypothesis, namely that Arctic sea ice loss weakens mid-latitude westerly winds, promoting more severe cold winters, has sparked more than a decade of scientific debate. The Polar Amplification Model Intercomparison Project was developed to address this issue and results from coordinated multi-model experiments will be presented that support the above hypothesis and suggest that this effect is underestimated by current models. However, even when accounting for this underestimation, the response to Arctic sea ice is small compared to yearly variations in mid-latitude winters.

For predictions to be useful they must be skilful and reliable. There is mounting evidence that models may underestimate the strength of predictable signals, especially for atmospheric circulation in the North Atlantic. This error has been termed the “signal-to-noise paradox” since it leads to the unexpected situation that models can predict the real world better than one of their own ensemble members. Skilful predictions can be achieved using a very large ensemble, but the model output cannot be taken at face value and needs calibrating to obtain skilful and reliable forecasts. Given the potential impacts of changes in atmospheric circulation, understanding why the signal-to-noise ratio is too small in current climate models, and assessing the extent to which correcting this model error would reduce uncertainties in regional climate change projections of the coming decades, are high priority areas for future research.

How to cite: Smith, D.: Decadal climate predictions, impacts of Arctic sea ice loss, and the signal-to-noise paradox, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2912, https://doi.org/10.5194/egusphere-egu22-2912, 2022.

Floods and droughts are often studied from a univariate perspective, which ignores their multivariate nature and can lead to risk under- or overestimation. The multivariate nature of hydrological extremes makes them particularly impactful, e.g. when they affect large areas or several components of the hydrological cycle, and should be considered when deriving frequency and magnitude estimates for hydraulic design and adaptation. However, studying multivariate extremes is challenging because different variables are related and because they are even less abundant in observational records than univariate extremes.
In this talk, I discuss different types of multivariate hydrological extremes and their dependencies including spatially co-occurring flood events, floods described by peak and volume, or droughts characterized by deficit and duration. I present different strategies to describe and model multivariate extremes, to assess their hazard potential, and to increase sample size – for example, the openly available R-package PRSim that stochastically simulates streamflow and hydrological extremes at multiple locations. I illustrate potential applications of some strategies using different large-sample datasets ranging from sets of alpine catchments in Switzerland to sets of hydro-climatologically diverse catchments in the United States and on the European continent. The strategies discussed enable a multivariate perspective in hydrological hazard assessments, which allows us to derive more comprehensive risk estimates than the classical univariate perspective commonly applied.

How to cite: Brunner, M. I.: Floods and droughts: a multivariate perspective on hazard estimation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3458, https://doi.org/10.5194/egusphere-egu22-3458, 2022.

How to cite: Buytaert, W.: Local solutions for global water security, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10506, https://doi.org/10.5194/egusphere-egu22-10506, 2022.

Geo- and environmental sciences produce a wide variety and numerous data which are extensively used both in fundamental research on Earth processes and in important real-life decision-making. Most natural phenomena are non-linear, multivariate, highly variable and correlated at many spatio-temporal scales. Analysis and treatment of such complex data and their integration/assimilation with science-based models is a difficult problem. Contemporary machine learning (ML) proposes an important set of effective approaches to address this problem at all phases of the study.

Nowadays, Geosciences are one of the major customers of ML ideas and technologies. To a large degree, it is connected to the local and global challenges facing humanity: sustainable development, biodiversity, social and natural hazards and risks, meteo- and climate forecasting, remote sensing Earth observation, etc. Despite being theoretically a universal modelling tool, the success of ML applications significantly depends on the problem formulation, quantity and quality of data and objectives of the study. Therefore, an efficient application of ML demands a good knowledge of the phenomena under study and a profound understanding of learning algorithms which can be achieved in close collaboration between experts in the corresponding domains.

In the current presentation, the study of geo- and environmental data using different machine learning algorithms is reviewed. A problem-oriented approach, which follows a generic data-driven methodology, is applied. The methodology consists of several important steps, in particular, optimization of monitoring and data collection, comprehensive exploratory data analysis and visualization, feature engineering and relevant variables selection, modelling with careful validation and testing, explanation and communication of the results. Advanced experimentation with data by using different supervised and unsupervised ML algorithms helps in better understanding of original data and constructed input feature space, obtaining more reliable and robust results and making intelligent decisions. The presentation is accompanied by simulated and real data case studies from natural hazards (avalanches, forest fires, landslides), environmental risks (pollution) and renewable energy assessment. In conclusion, some general remarks and future perspectives are discussed.

How to cite: Kanevski, M.: On Machine Learning from Environmental Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6482, https://doi.org/10.5194/egusphere-egu22-6482, 2022.

Today's climate science is being driven by IT more than ever. Earth system models on high-performance computers (HPC) are common tools for researching the past and projecting it into the future. In addition to that, statistical modelling is reborn thanks to modern computer architectures equipped with artificial intelligence (from ensemble to deep learning). Future advances in machine learning will also shape climate research through analysis tools, prediction techniques, signal and event classification, post-processing, Model Output Statistics (MOS), evaluation and verification, etc. This presentation will look at nowadays research about the future (part one) and the past (part two) of our climate system using AI/ML ideas and technologies in combination with numerical climate models - from two publications accordingly. A special focus will be on the importance of climate science, where the needs are, and how to choose the AI/ML hammer wisely:

(1) FUTURE: Derived from machine (ensemble) learning and bagging, a new hybrid climate prediction technique called 'Ensemble Dispersion Filter' is developed. It exploits two important climate prediction paradigms: the ocean's heat capacity and the advantage of the ensemble mean. The Ensemble Dispersion Filter averages the ocean temperatures of the ensemble members every three months, uses this ensemble mean as a restart condition for each member, and further executes the prediction. The evaluation  shows that the Ensemble Dispersion Filter results in a significant improvement in the predictive skill compared to the unfiltered reference system. Even in comparison with prediction systems of a larger ensemble size and higher resolution, the Ensemble Dispersion Filter system performs better. In particular, the prediction of the global average temperature of the forecast years 2 to 5 shows a significant skill improvement.

Kadow, C., Illing, S., Kröner, I., Ulbrich, U., and Cubasch, U. (2017), Decadal climate predictions improved by ocean ensemble dispersion filtering, J. Adv. Model. Earth Syst., 9, 1138– 1149, doi:10.1002/2016MS000787. 

(2) PAST: Nowadays climate change research relies on climate information of the past. Historic climate records of temperature observations form global gridded datasets like HadCRUT4, which is investigated e.g. in the IPCC reports. However, record combining data-sets are sparse in the past. Even today they contain missing values. Here we show that artificial intelligence (AI) technology can be applied to reconstruct these missing climate values. We found that recently successful image inpainting technologies, using partial convolutions in a CUDA accelerated deep neural network, can be trained by 20CR reanalysis and CMIP5 experiments. The derived AI networks are capable to independently reconstruct artificially trimmed versions of 20CR and CMIP5 in grid space for every given month using the HadCRUT4 missing value mask. The evaluation reaches high temporal correlations and low errors for the global mean temperature.

Kadow, C., Hall, D.M. & Ulbrich, U. Artificial intelligence reconstructs missing climate information. Nat. Geosci. 13, 408–413 (2020). https://doi.org/10.1038/s41561-020-0582-5

How to cite: Kadow, C., Hall, D. M., Ulbrich, U., Kröner, I., Illing, S., and Cubasch, U.: Artificial Intelligence and Earth System Modeling - revisiting Research of the Past and Future, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12895, https://doi.org/10.5194/egusphere-egu22-12895, 2022.

Pelagic sediments are boring as they result from monotonous processes: after death, calcareous and/or siliceous phytoplankton and zooplankton (with minor contributions of clayey particles) very slowly settle on the ocean floor. Pelagic sedimentation, therefore, closely corresponds to the productivity of surface waters while being controlled by ocean chemistry, fertility, temperature and depth-size of the basin. The biological pump extracts nutrients and carbon from the photic zone to form organic matter which, however, fails to reach the deep ocean, unless exceptionally unusual conditions are established. Some phytoplanktonic organisms, though, have invented biomineralization and many mineralized parts accumulate at the seafloor as oozes, later diagenetically transformed into pelagic limestone and, more sporadically, chert.  

Arguably, the modern ocean originated in the Early Triassic when a group of phytoplankton learned, by chance or by necessity, to calcify. Since then, coccolithophores developed the ability to secrete a variety of coccoliths/nannoliths and coccospheres. Coccolithogenesis, in a sense, continued to take snapshots that we can use to assess the functioning and dynamics - at various time resolutions- of the ocean, the largest and oldest ecosystem on our planet. My talk will try to provide data and interpretations of good and bad times for Mesozoic coccolithophores, with the ultimate goal of sharing with you my understanding of what a "normal" ocean was, what was its resilience to global perturbations, and which were the tipping points.In Jurassic and Cretaceous oceans calcareous nannoplankton were already widespread from coastal to open oceanic settings and of enough abundance and diversity to be rock-forming. Their variations somehow correlate with environmental global change, although getting from correlation to causality is not always straight forward. Mesozoic ocean anoxic events (OAEs) represent some of the most dramatic disruptions of the global carbon cycle and the geological records of OAEs have been thoroughly investigated to understand how the Earth system has overcome such extreme stress. Quantitative studies reveal major shifts in nannofossil assemblages with species-specific variations in size and major decreases in abundance, especially of the dominant rock-forming taxa. The absence/rarity of calcareous nannofossils at the peak of the OAE perturbation is primarily interpreted as the result of a major change in ocean alkalinity (and development of acidification) that possibly hindered biocalcification. However, none of the nannoplankton forms experiencing a calcification crisis got extinct: they recovered when the paleoenvironment returned to a pre-perturbation state, although slowly and partially.

Calcareous nannoplankton evolution is marked by spectacular speciation episodes (some of them anticipating and accompanying OAEs) in absence of extinctions. Furthermore, Jurassic and Cretaceous nannoplankton underwent accelerated originations during times of prolonged stability that, apparently, may have triggered innovative ways of coccolith/nannolith calcification. After decades of research devoted to environmental perturbations, we know very little about the unstressed ocean. Yet to understand/model how to stop and/or reverse the current global change, we should first know the characteristics of a calm, stable, normal ocean. What concentrations of atmospheric CO2? What fluctuations in chemistry, fertility, temperature? What variations in marine biota? The answers are written in the boring pelagic limestones!

How to cite: Erba, E.: Tiniest story-tellers of the largest ecosystem: calcareous nannofossils and the Mesozoic ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2899, https://doi.org/10.5194/egusphere-egu22-2899, 2022.

Droughts have major economic, social and environmental impacts around the world, and they are expected to increase in severity and magnitude because of changes in climate and its variability. In recent years we have seen incredible developments in the field of drought research and we have significantly improved our understanding of this complex phenomenon. While observations have become more abundant, we have also seen significant improvements in hydrological models that are better constrained by these observations. These model improvements also include the addition of new, relevant processes, needed to fully understand drought feedbacks.

In this talk I will discuss my experience with modeling drought at larger scales and including human-water interactions at these scales. These models are also used to study the impact of climate change on drought and show the impact of rising temperatures on society’s exposure to these impactful events. Spatial resolutions of hydrological models have improved significantly and the complexity of processes that we are able to simulate has increased, leading to exciting new insights. At the same time, we have to communicate these findings with not only the scientific community, but also the general public. This brings new challenges for scientists and affects our science.

I’ll highlight recent advances in the field of drought research and hydrological modelling, as well as frontiers and interesting developments in the field. I’ll mention some key challenges that we still have to face to better understand the impact and feedbacks of extreme hydroclimatic events.

How to cite: Wanders, N.: Dry drier drought – Understanding drought in a changing society and climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3416, https://doi.org/10.5194/egusphere-egu22-3416, 2022.

Thermal infrared (TIR) and visible/near-infrared (VNIR) surface reflectance imagery from remote sensing can be effectively combined in surface energy balance models to map evapotranspiration (ET) and vegetation stress, with broad applications in agriculture, forestry, and water resource management. Particularly valuable are ET retrievals at medium resolution (100 m or finer), resolving scales at which water and land are actively managed over much of the Earth’s surface. At this scale, TIR and VNIR data in the Landsat archive provide a 40-year and growing global record of coupled land and water use change.  In this presentation we will discuss the unique information content conveyed by the land-surface temperature signal regarding the surface moisture status and vegetation health. We will explore applications for field-scale temperature and ET retrievals in promoting sustainable water use, forest health, and regenerative agricultural practices. Widespread and routine generation of ET data at this scale has been enabled by cloud computing technologies, with the OpenET ensemble modeling platform as an example of collaborative geospatial information development.  Looking forward, integration of Landsat with new sources of medium-resolution TIR imagery (e.g., ECOSTRESS, LSTM, TRISHNA, SBG, Landsat-Next, and Hydrosat), as well as all-sky microwave-based temperature retrievals, will improve our ability to detect rapid changes in water use and availability – a key factor in real-time decision making.

How to cite: Anderson, M., Yang, Y., Xue, J., Knipper, K., Yang, Y., Gao, F., Hain, C., Holmes, T., Kustas, W., Fischer, M., and Trnk, M.: On the value of thermal infrared remote sensing for water and land management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6797, https://doi.org/10.5194/egusphere-egu22-6797, 2022.

Accurate mapping of subglacial bedrock topography is of prime importance to correctly simulate the past and future evolution of glaciers and ice sheets. As ocean warming is a major driver of recent changes in Greenland and Antarctica, mapping the bathymetry of the ocean seafloor in fjords and underneath ice shelves is crucial to accurately model warm water pathways up to the ice margins and grounding lines. A good knowledge of this bedrock topography also allows to better understand the past extent of the ice sheets and identify vulnerable regions that are sitting on retrograde bed slopes, hence that might be prone to the marine ice sheet instability. For mountain glaciers, accurately mapping the bedrock topography is mandatory to estimate ice thicknesses, which are used to simulate the contribution of glaciers to sea level rise, but also to quantify the amount of freshwater resources stored in glaciers. Because of their large number, remote locations, and difficult access conditions, only scarce in-situ data exists for bedrock topography. Hence, while being a fundamental variable for glacier modeling, it remains poorly constrained at the time. Here, we present how the use of multiple sensors remote sensing techniques has helped us to unravel the hidden relief beneath glaciers and ice sheets. In Greenland and Antarctica, we use airborne gravimetry measurements along with multibeam and radar echoe sounder to map the bathymetry in fjords and below ice shelves. We show that the use of these new bathymetric products help us to understand the retreat history of glaciers, revealing pathways for warm water, and contributes to better modeling ocean circulation up to the grounding lines of glaciers. For mountain glaciers, we mapped the ice velocity worldwide at an enhanced sampling resolution of 50 m, using massive cross correlation techniques on image pairs from both optical (ESA’s Sentinel-2; USGS/NASA’s Landsat-7/8) and radar imagery (ESA’s Sentinel-1a/b). Finally, we combine this mapping with airborne and ground penetrating radar to recover the ice thickness of all glaciers on Earth. These estimations reveal a different picture of the bedrock topography beneath glaciers, with a modified ice thickness distribution. Using these new estimations as initial state in the Open Global Glacier Model, we show the important impact on the evolution of freshwater resources, and specifically on the timing of the peak water.

How to cite: Millan, R., Mouginot, J., Morlighem, M., Rabatel, A., Gimenes, L., Champollion, N., Rignot, E., An, L., and Bjørk, A.: Insights of multiple sensors remote sensing techniques for the mapping of subglacial valleys beneath glaciers and ice shelves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1321, https://doi.org/10.5194/egusphere-egu22-1321, 2022.

Concurrent with atmospheric warming, glaciers around the world are rapidly retreating with direct consequences for global sea level and streamflow. Projections indicate considerable mass losses over the 21st century, however, mass losses vary strongly between regions and emission scenarios. In some regions with little ice cover projections forced by high emission scenarios show almost complete deglaciation by the end of the 21st century while in high-polar regions the relative mass losses are generally in the order of a few tenths of percent relative to year 2015. The mass losses alter local runoff regimes and lead to glacier runoff increases in some regions but to decreases in others. Global glacier changes are linearly correlated with global mean temperature increase indicating that limiting global warming has a direct effect on future glacier mass changes.

How to cite: Hock, R.: Future global glacier mass changes and their impact on sea level and streamflow, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6431, https://doi.org/10.5194/egusphere-egu22-6431, 2022.

In 1963 Lorenz discovered what is usually known as “chaos”, that is the sensitive dependence of deterministic chaotic systems upon initial conditions. Since then, this concept has been strictly related to the notion of unpredictability pioneered by Lorenz. However, one of the most interesting and unknown facets of Lorenz ideas is that multiscale fluid flows could spontaneously lose their deterministic nature and become intrinsically random. This effect is radically different from chaos. Turbulent flows are the natural systems when Lorenz ideas can be touched by the hand. They can, indeed, be described via the Navier-Stokes equations, thus conforming to the class of deterministic dissipative systems, as well as, present rich dynamics originating from non-trivial energy fluxes in scale space, non-stationary forcings and geometrical constraints. This complexity appears via non-hyperbolic chaos, randomness, state-dependent persistence and predictability. All these features have prevented a full characterization of the underlying turbulent (stochastic) attractor, which will be the key object to unpin this complexity. 

Here we use a novel formalism to map unstable fixed points to singularities of turbulent flows and to trace the evolution of their structural characteristics when moving from small to large scales and vice versa, providing a full characterization of the attractor. We demonstrate that the properties of the dynamically invariant objects depend on the scale we are focusing on. Our results provide evidence that the large-scale properties of turbulent flows display universal statistical properties that are triggered by, but independent of specific physical properties at small scales. Given the changing nature of such attractors in time, space and scale spaces, we term them chameleon attractors.

How to cite: Alberti, T.: The geometry of scales: chameleon attractors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1090, https://doi.org/10.5194/egusphere-egu22-1090, 2022.

Many systems in nature are characterized by the coexistence of different stable states for a given set of environmental parameters and external forcing. Examples for such behavior can be found in different fields of science ranging from mechanical or chemical systems to ecosystem and climate dynamics. As a consequence of the coexistence of a multitude of stable states, the final state of the system depends strongly on the initial condition.  Perturbations, applied to those natural systems can lead to critical transitions from one stable state to another. Such critical transitions are called tipping phenomena in climate science, regime shifts in ecology. They can happen in various ways: (1) due to bifurcations, i.e. changes in the dynamics when external forcing or parameters are varied extremely slow, (2) due to fluctuations which are always inevitable in natural systems, (3) due to rate-induced transitions, i.e. when external forcing changes on characteristic time scales comparable to the intrinsic time scale of the considered dynamical system and (4) due to shocks or extreme events. We discuss these critical transitions and their characteristics and illustrate them with examples from climate science and ecosystem dynamics. Moreover, we discuss the concept of resilience, which has been originally introduced by C.S. Holling in ecology, and formulate it in terms of dynamical systems theory. This formulation offers mathematical and numerical tools to use it as a measure of the persistence of a function of a dynamical system.

How to cite: Feudel, U.: Tipping phenomena and resilience of complex systems: Theory and applications to the earth system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10567, https://doi.org/10.5194/egusphere-egu22-10567, 2022.

Earth’s magnetic field is a long-lived phenomenon generated by dynamo processes occurring in the liquid core. Understanding how the strength of the field changes in time and space is critical to gaining insight into processes in Earth’s core and deep interior. The publication of field strength estimates represents a significant output of the paleomagnetic community, with efforts spanning several decades and dozens of research groups. Recently, the site-mean absolute paleointensity database PINT (www.pintdb.org; Bono et al., GJI, 2022) received a major update to include data published up through 2019 and fully integrates the Quality of Paleointensity (Q_PI) assessments for 94% of the database. Interpreting the paleointensity record as a continuous record of Earth’s field is challenging because of the non-uniformly spaced, often sparse, data records and the combination of natural variation of field strength due to secular variation and measurement uncertainty. Here, we have used the PINT database to construct a continuous paleomagnetic axial dipole moment model spanning 0.05 to 3500 Ma, MCADAM v1.0 (Monte Carlo Axial Dipole Average Model). The dipole moment model applies three resampling approaches: a non-parametric resampling (akin to a bootstrap) of site-mean records, a Monte Carlo simulation of site-mean estimates using age and paleointensity means and uncertainties, and LOWESS smoothing with an adaptative kernel width. These methods are combined to provide posterior predictions of axial dipole field strength and allow for estimation of the median field with confidence bounds. This approach can reproduce the recent (0-2 Ma) field that matches PADM2M (Ziegler et al., GJI, 2011) as well as salient field intervals (e.g., high fields associated with superchrons) during the Phanerozoic. The model also reveals changes in field strength during the Precambrian which may be used to help constrain dynamo simulations and thermal evolution models of Earth’s core.

How to cite: Bono, R., Paterson, G., and Biggin, A.: MCADAM: A continuous paleomagnetic dipole moment model for the past 3.5 billion years using the PINT v8.0.0 database, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6157, https://doi.org/10.5194/egusphere-egu22-6157, 2022.

Brittle failure of intact rock and frictional sliding on faults are closely related. Much of my early career studying brittle failure using acoustic emission techniques was helpful in providing insight into processes associated with faulting and earthquakes. While I was focusing on failure processes with my colleague and mentor, Jim Byerlee, the basic tenants of what is referred to as rate- and state-dependent friction (RS) were being developed literally next door by Jim Dieterich with Andy Ruina and many others. It was a remarkable period in Menlo Park in the late ‘70s and ‘80s for which I had only limited appreciation at the time. While it is easy to reminisce, it is more useful to take stock of our current understanding of earthquake processes; what we have achieved and how very much farther we have to go. For example, one long-standing goal that remains elusive is earthquake prediction. While long term forecasting is clearly improving, prediction within hours to days remains out of reach. From a laboratory perspective, with tight control of fault roughness, stress, temperature, fluid pressure and other variables, prediction of timing and magnitude are possible, but with notable restrictions.

Rate- and state-dependent friction, for example, has been useful in the analysis of numerous earthquake-related phenomena including earthquake nucleation, earthquake triggering, slow slip, and repeating earthquakes. At the same time, it should be recognized that the RS model was developed using dry, planar laboratory faults at modest normal stress and limited total displacement. Along with the many successes of RS friction, it is useful to consider some of the limitations. Examples include (1) strain hardening- observed in most laboratory experiments as initial fault surfaces undergo rapid and irreversible changes in roughness and fault gouge properties; (2) melt formation or flash heating – where self-heating due to rapid sliding alters surface properties; and (3) hydro-mechanical coupling of low permeability faults where frictional heating increases pore fluid pressure or changes in porosity lead to transient dilatancy-strengthening or compaction-weakening.

I will present laboratory observations of fault strength evolution that are beyond the scope of standard RS formalism. Examples include constant loading rate tests near critical stiffness in which deformation mode spontaneously jumps between sequences of stable slow-slip oscillations and unstable stick-slip. In a second example with a hydraulically isolated, water-saturated fault gouge, incremental increases in slip rate lead to dilatancy, pore pressure decrease and fault stabilization. However, larger jumps in velocity lead to porosity collapse, fluid pressurization and fault instability. Hydrothermal slide-hold-slide tests at 200 °C, 10 MPa deionized water pressure and 30 MPa confining pressure produce the usual log-linear healing rate for hold times less than 5,000 s. Longer hold times, however, show increased weakening. Apparently, an overall time-dependent weakening of the fault surface occurs that dominates instantaneous fault strengthening for long hold periods and requires hundreds of microns of slip to be erased. These examples suggest that extrapolation of R/S models from idealized laboratory conditions to natural fault conditions may lead to erroneous predictions.

How to cite: Lockner, D.: A Laboratory Perspective on Earthquake Nucleation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8972, https://doi.org/10.5194/egusphere-egu22-8972, 2022.

The use of experimental tectonics (also known as analogue-, laboratory, or physical modelling) to study tectonic processes is not a novelty in Earth Science. Following Sir James Hall’s pioneer work (1815), many modellers squeezed, stretched, pushed and pulled a wide range of materials – e.g., sand, clay, oil, painters’ putties, gelatins, wax, paraffin, syrups, polymers – to unravel a wide range of tectonic processes to determine parameters controlling their geometry, kinematics and dynamics. However, only recently experimental analogue modelling has definitively transformed from a qualitative to a quantitative technique, thanks to appropriate scaling relationships, the improvement in the knowledge of the rheology of both natural and analogue materials and the use of high-resolution monitoring techniques to quantify morphology, kinematics, stress, strain and temperature.

Here, I specifically review the experimental work performed to study one of the most intriguing aspects of plate tectonics: the subduction process. Subduction provides the dominant engine for plate tectonics and mantle dynamics. Moreover, it has also societal importance playing a key role on hazard at short (i.e., earthquakes and mega-earthquakes, tsunami, effusive and explosive volcanic activities with impact on aviation safety) and long time scales (i.e., local and global climate change). Over the last decades, a noteworthy advance in the quality and density of global geological, geophysical and experimental data has allowed us to provide systematic quantitative analyses of global subduction zones and to speculate on their behaviour. These constraints have been integrated into a mechanical framework through modelling.

I will bring you to a journey through the past, the present and the future of analogue modelling and related efforts, results and perspectives for the study of the subduction process. It will be shown how analogue models, with their inherent 3D character and behaviour driven by simple and natural physical laws, contribute to successfully unravelling the subduction process, inspiring new ideas. Challenging ongoing perspectives of analogue models imply the possibility to compare time and space scales, allowing to merge, within the same model, both short- and long-term and shallow and deep processes.

How to cite: Funiciello, F.: Analogue modelling of subduction: yesterday, today and tomorrow., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13304, https://doi.org/10.5194/egusphere-egu22-13304, 2022.

  The Milankovitch Theory of orbital climate change postulates that changes in the caloric summer half-year insolation (or Northern Hemisphere summer insolation (NHSI) at ~65°N latitude) drive changes in the ice-sheets extent (i.e., global ice-volume) at Earth’s orbital periods (i.e., the sensu-stricto theory). These insolation-driven changes in turn, incite ancillary changes in other parts of the global climate systems via various forcing and feedback mechanisms (the sensu-lato hypothesis). In this theoretical framework the high-latitude glaciation processes took the center stage while the low-latitude global monsoon was essentially excluded. In the last two decades, large numbers of cave d¹⁸O records with precise radiometric chronologies have propelled speleothems to the forefront of paleoclimatology. Of particular interest are the speleothem records from North America that reveal a persistent orbital pacing of the North American climate at the precession band, which is nearly in phase with changes in the global ice-volume and atmospheric CO₂ but lags June insolation at 65°N by ~5000 years, in accordance with the sensu-stricto Milankovitch theory. Contrastingly, the low-latitude tropical speleothem records manifest an orbital-scale pattern of global monsoon, which is dominated by precession cycles with a nearly anti-phased relation between the two hemispheres. Importantly, the monsoon variations track summer (July/January) insolation without significant lags at the precession band. We thus suggest that precession-induced changes in summer insolation produce distinct climate variability in the ice-sheet proximal and tropical regions predominantly via the (delayed) ice-volume/CO₂ forcing/feedbacks and nearly-in-phase monsoon/CH₄ responses/feedbacks.

  As for global-scale millennial events that were superimposed on orbital-scale climate variations, the essence of these events—i.e., conventional ice age terminations and other smaller events (the so-called ‘low-amplitude versions of terminations’), is virtually similar. The time-series of millennial-scale variations after removing orbital insolation signals from the speleothem monsoon record and long-term trend in the Antarctic ice core temperature (δD) record characterize the millennial climate variances of both ice age termination and low-amplitude versions of termination events. Remarkably, the millennial-scale variations show significant obliquity and precession cycles that are in-phase with North Hemisphere June insolation, implying a critical role of changes in orbital insolation in triggering the ice age terminations. These observations, in turn, provide new insights into the classic ‘100 ka problem’.

  Indeed, a more comprehensive picture of orbital theory of climate is steadily emerging with the growth of new geological proxy data, particularly the low-latitude speleothem data from the vast global monsoon regime, providing critical complements to marine and ice-core data.

How to cite: Cheng, H.: Milankovitch Theory and Global Monsoon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1422, https://doi.org/10.5194/egusphere-egu22-1422, 2022.

Forest soils are undeniably recognized to help deliver essential ecosystem services. Nevertheless this provision is facing serious threats at a moment we need forests the most. The increasing frequency of fire-prone weather conditions in the EU such as the ones causing exceptional wildfire scars in 2017 (San-Miguel-Ayanz et al., 2018), combined with extreme climate demands (IPCC, 2021) and an escalation of forest mechanisation driven by a systematic increase in the use of forest products (EUROSTAT, 2021), have been putting  EU forest soils to a new level of pressure. As a result, key ecosystem services such as clean water provision and flood control, habitats for life and biodiversity,  biomass provision and carbon sinks, are at stake.

On the other hand, several positive policy initiatives have been initiated under the umbrella of the European Green deal, such as the EU Forest and Biodiversity strategies for 2030. These aim for more healthy, diverse and resilient EU forests, ensuring we can count on their contribution for the most recent climate and biodiversity ambitions. Such initiatives combined with the new EU Soil Strategy should underpin a new era of ecosystems resilience and halt the latest land degradation trends. But the question remains: what is the current state of the EU forest soils after so many years of coexistence with the Europeans?

This presentations aims to provide an overall perspective on current threats affecting forest soils. Issues such as recurrent wildfires, inappropriate land management, land use and land cover changes are all sides of the same coin. Not surprisingly these will lead to land degradation, triggered most frequently by soil erosion. In addition, this paper will identify several misconceptions driven by remote sensing based assessments, such as the identification of good soil conditions under vigorous leaf area indexes, or the consideration of good soil management practices in all forest terraces.

With this argumentation the author hopes to trigger a healthy discussion on the idea that our EU forest soils are not in their best shape, and they too need to be cared for and managed. 

How to cite: Vieira, D.: Forest soils under threat too., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3542, https://doi.org/10.5194/egusphere-egu22-3542, 2022.

Plant roots and the organisms that surround them are a primary source for stabilized soil organic carbon (SOC). While grassland soils have a large capacity to store organic carbon (C), few field-based studies have quantified the amount of plant-fixed C that moves into soil and persists belowground over multiple years. Yet this characteristic of the soil C cycle is critical to C storage, soil water holding capacity and nutrient provisions, and the management of soil health. We tracked the fate of plant-fixed C following a five-day ¹³CO₂labeling of a Northern California annual grassland, measuring C pools starting at the end of the labeling period, at three days, four weeks, six months, one year, and two years. Soil organic carbon was fractionated using a density-based approach to separate the free-light fraction (FLF), occluded-light fraction (OLF), and heavy fraction (HF). Using isotope ratio mass spectrometry, we measured ¹³C enrichment and total C content for plant shoots, roots, soil, soil dissolved organic carbon (DOC), and the FLF, OLF, and HF. The chemical nature of C in the HF was further analyzed by solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy.
At the end of the labeling period, a substantial portion of the ¹³C (40%) was already found belowground in roots, soil, and soil DOC. By 4 weeks, the highest isotope enrichment and 27% of the total amount of ¹³C remaining in the system was associated with the mineral-rich HF. At the 6-month sampling—after the dry summer period during which plants senesced and died—the amount of label in the FLF increased to an amount similar to that in the HF. The FLF ¹³C then declined substantially by 1 year and further decreased in the 2^ndyear. By the end of the 2-year experiment, 67% of remaining label was in the HF, with 19% in the FLF and 14% in the OLF.
While the ¹³C content in the HF was stable over the final year, the chemical forms associated with the HF evolved with time. The relative proportion of aliphatic/alkyl C functional groups declined in the newly formed SOC over the 2-years in the field; simultaneously, aromatic and carbonyl/carboxylic C functional groups increased and the proportion of carbohydrate (O-alkyl C) groups remained relatively constant.
Our results indicate that plant-fixed C moved into soil within days of its fixation and was associated with the soil mineral fraction within weeks. While most of the annual plant C input in these grasslands cycles rapidly (<2-year timescale), a sizeable proportion (about 23% of the ¹³C present at day 0) persisted in the soil for longer than 2 years. While decadal studies would allow improved assessment of the long-term stabilization of newly fixed plant C, our 2-year field study reveals surprisingly rapid movement of plant C into the HF of soil, followed by subsequent evolution of the chemical forms of organic C in the HF.

How to cite: Firestone, M., Fossum, C., Estera-Molina, K., Yuan, M., Herman, D., Chu-Jacoby, I., Nico, P., Morrison, K., and Pett-Ridge, J.: Belowground allocation and dynamics of recently fixed plant carbon in a California annual grassland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13569, https://doi.org/10.5194/egusphere-egu22-13569, 2022.

Mineral dust, one of the most abundant aerosols in the atmosphere, can be transported by winds thousands of kilometers away from its source and deposited on land and sea. In response to growing societal interest in reducing risks from various hazardous dust effects, the World Meteorological Organization has established a long-lasting Sand and Dust Storm Warning Advisory and Assessment System, while the UN formed in 2018 the Coalition to Combat Sand and Dust Storms. Over the last twenty years, thanks to dust-related research, numerical models have been developed which today successfully predict the atmospheric dust process. Such models include dust concentration as a prognostic parameter and can now successfully assess the occurrence of most dust storms. There are numerous impacts of dust on weather, climate, marine and terrestrial ecosystems, many of them with detrimental effects, such as: adverse influence on human health; disruption of ground and aviation transport; reduced agricultural growth; disfunctioning of solar energy panels; and acceleration of snow and ice melting in high-latitudes. This study will present examples illustrating recent efforts to develop user-oriented applications based on the use of dust forecasting products to mitigate the negative impacts of this aerosol.

How to cite: Nickovic, S.: Numerical prediction of the atmospheric dust process: the way to reduce risks from its adverse effect, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13258, https://doi.org/10.5194/egusphere-egu22-13258, 2022.

What does it mean for a landscape to be sustainable? And what does sustainability mean for the people living on the landscape? As we address whether landscapes are sustainable or under which conditions sustainability can be achieved, it is important to realize that the view we get at system scale can be very different from the view at human scale. Sustainability can mean different things for the system and for the people living on it. The connector between these two views is the river network itself, which is responsible for the distribution of fluxes of water, sediment, and nutrients across the landscape. A leaky river network  connects channels and their floodplains, a fundamental property for the construction and maintenance of floodplains and delta plains. In this lecture, I will cover the analysis of landscapes across scales with particular focus on river deltas: what we learn from a system view, what happens at the local/human scale, and how the network fills the gap between these two views. I will also discuss which opportunities exist to inform delta sustainability from studies combining remote sensing, modeling, and field observations. Flux partitioning along delta networks, hot spots of change, and associated rates of change need to be quantified and this information integrated into adaptive delta management strategies for future climate scenarios.

How to cite: Passalacqua, P.: Towards sustainable landscapes: insights from the network and connectivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2073, https://doi.org/10.5194/egusphere-egu22-2073, 2022.

The geochemical toolkit is pertinent to fields other than that of Earth and Planetary Sciences for which it is traditionally and commonly used. Here we show two recent examples of its application to numismatics, archaeology, and ancient history. High-precision Pb isotopes treated by novel statistical tools were used to provide data-based answers to important research questions revolving around the sources of silver used for money, jewelry, and other valuable artefacts in the ancient world.

In the first example, we studied remnants of the silver making up the largest treasure of precious metals reported in ancient Western history, namely that of Alexander the Great which he looted in his conquest of the Persian Empire, by analyzing a large set of ancient silver coins (alexanders, sigloi, Greek coins, and early Indian pseudo-coinage) for their Pb isotopic compositions. The high-precision data were treated using a new statistical approach in the form of calculated Pb model ages combined with cluster analysis and convex-hull theory, which allows the tracking of silver provenance with greater accuracy and precision than was previously possible when using only raw Pb isotope ratios and manually comparing artefacts with known ores on a one-to-one basis. Based on the Pb isotopic compositions of the analyzed silver coins compared with a ca. 6700-entry Pb isotope database on ores that we have compiled from the literature and our own work, we established that the bulk of the silver sources can be traced to the southern Aegean, Macedonia, and Thrace [1]. These origins had so-far only been the subject of speculation by numismatists, archaeologists, and historians, whereas now they are supported by high-precision isotope data and objective data analysis. Furthermore, we were able to confidently exclude India as a source [1], thereby putting to rest a long-standing debate around a possible Indian silver contribution to the Persian treasury.

In the second example [2], we measured high-precision Pb isotopes on pieces of hoarded Hacksilber (irregularly cut silver bullion) in the southern Levant, which facilitated trade and transactions from the beginning of the second millennium BCE until the late fourth century BCE. In a similar fashion to the first example, we treated the data using cluster analysis and convex-hull theory applied to Pb model ages calculated from measured high-precision Pb isotopic compositions. We found that exchanges between the Levant and the Aegean world continued at least intermittently from the Late Bronze Age through to the Iron Age III. Importantly, contrary to common belief that silver trade had come to an end following the Late Bronze Age collapse, we demonstrated that despite the Aegean world dominating silver supply during the Iron Age, exchanges between the eastern and the western Mediterranean did not cease altogether. People around the Mediterranean remained connected with silver flowing to the Levant possibly as a result of trade or plunder.

[1] Blichert-Toft, J., de Callatay, F., Télouk, P., Albarède, F., submitted. J. Archaeo. Meth. Theo.

[2] Gentelli, L., Blichert-Toft, J., Davis, G., Gitler, H., Albarède, F., 2021. J. Archaeo. Sci. 134, Article 105472.

How to cite: Blichert-Toft, J., Gentelli, L., Davis, G., Gitler, H., de Callataÿ, F., and Albarède, F.: When Geochemistry encounters Archaeology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1035, https://doi.org/10.5194/egusphere-egu22-1035, 2022.

The controls on the style of silicic eruptions – hazardously explosive, more gently effusive, or hybrid explosive-effusive – are poorly constrained. Current models invoke escape of gas through a connected foam, or through fractures, as the primary mechanism for the transition from explosive to effusive eruption. We propose a new model, in which hybrid and effusive silicic eruptions are typically explosive at depth, but the clastic products of this 'cryptic fragmentation' sinter and weld in the conduit to produce coherent lava at the surface. Drawing on numerous case studies of natural textures within eruptive products and dissected conduits, we show that effusive silicic eruptions are best interpreted as being the welded, squeezed-out remnant of ongoing or recent subsurface explosive behaviour. We demonstrate that effusively erupted lavas have microtextures diagnostic of a welding/sintering genesis and are comparable with those found in rheomorphic and welded ignimbrites. All eruptive products share pore network geometries and associated mechanical and hydraulic property-porosity relationships that are consistent with models for sintered materials. We conclude that silicic lava is generally clastogenic, and that, after it is sinter-assembled, it may undergo gas-driven fracturing that produces lava plug-cutting tuffisites (closed fractures filled with sintered particles), and sintered pyroclasts (from ash- to bomb-sized). At some sites (e.g. Volcán Chaitén 2008), the first material to be extruded from the vent is a pyroclastic rubble similar texturally to the volcanic bombs from the same site. We propose therefore that the shallow conduit is filled with pyroclastic and lithic rubble; a volume that variably compacts over time to produce a plug of densified lava. Envisaging the shallow conduit as a compacting rubble pile instead of a coherent magma-filled pipe or crack leads us to posit that the explosive-effusive transition is a blurred behavioural switch controlled by the competition between material supply at the underlying fragmentation front, and shallow particle capture, welding and lava production above. This framework has broad top-down implications for geochemical and geophysical predictions of shallow silicic volcanism, which we will explore in this presentation.

How to cite: Wadsworth, F. B., Llewellin, E. W., Vasseur, J., Gardner, J. E., and Tuffen, H.: A reappraisal of explosive-effusive silicic eruption dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13600, https://doi.org/10.5194/egusphere-egu22-13600, 2022.

One of the great challenges facing our society is to cope with the increase in natural risks induced by climate change and human activity. The frequency of heavy rains and changes in vegetation cover have intensified over most areas, leading to enhanced risks of landslides and the tsunamis they can generate. Rising sea levels, partly induced by polar ice mass loss due to ice sheet melting and iceberg calving, make the increasing coastal population and infrastructures even more vulnerable to tsunamis. This creates an urgent need for precise quantification of landslides, tsunamis, and sea level rise impact to build reliable hazard maps for early warning systems and evacuation plans.

Accurate prediction of landslides and ice sheet mass loss is usually unreachable despite a tremendous amount of high quality data from imagery, GPS and dense arrays of seismic and oceanic sensors that record the seismic and water waves generated by landslides and iceberg calving at distances of more than 1000 km from the source, depending on the event volume (m³ to km³). These waves carry key information on the source such as mobilized mass, friction of the sliding material, and interaction with water. Therefore, beyond mere detection and localization of landslides and iceberg calving, full exploitation of these wave data should provide unprecedented clues to the complex characteristics and dynamics of these sources. Despite increasing research in environmental seismology this last decade, this is still a highly challenging issue because of the complexity of natural processes and their intricate imprint on wave characteristics. Until recently, only very simplified models have been used to simulate the generated seismic signal, making it difficult to separate the effects of model uncertainties or other parameters such as topography, flow dynamics, and wave propagation on the recorded signal. In parallel to environmental seismology, key advances are being made in the mechanics of granular materials, mathematics, and computing capacity.

By bridging geophysics, mathematics, and mechanics, we have developed sophisticated source models describing granular flows over complex topography.  By coupling them with seismic wave propagation models, we have shown that the low frequency seismic signal can be simulated and inverted to constrain the flow dynamics, rheological properties, and physical processes involved. In a similar way, we have quantified ice mass loss due to calving in Greenland over the last twenty years by coupling the inversion of seismic waves with advanced modeling of iceberg calving. To illustrate this multidisciplinary approach, I will present recent laboratory experiments and numerical modeling of granular flows, iceberg calving, and emitted seismic waves. In particular, I will demonstrate the key role of topography, rheology, erosion, and solid/fluid interaction in these phenomena and generated waves, as well as the challenges in their accurate description in numerical models applicable at the field scale at tractable computational costs.  Addressing these issues in the future will break new ground in the detection and modeling of landslides, tsunamis, and glaciers, leading to improved assessment of related hazards and the quantification of their link with climatic, seismic, and volcanic activity.

How to cite: Mangeney, A. and the multidisciplinary group of her collaborators: Challenges in physical modeling of landslides, glaciers, and generated seismic and tsunami waves for hazard assessment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4490, https://doi.org/10.5194/egusphere-egu22-4490, 2022.

In this presentation a kaleidoscopic overview of some geodetic inferential challenges and opportunities will be given. The topics addressed are (1) Interferometric inference; (2) Distributive computing; and (3) Predictive quality. They represent samples of fertile grounds for the typical researcher (PhD student and Postdoc alike) interested in geodetic data processing and modelling, and eager to take up a difficult challenge and/or looking for research opportunities that can make a difference.

Interferometric inference: Although considerable advances have been made in this field, particularly through the very successful global research in interferometric-GNSS, important challenges posed by our mixed-integer models remain. These challenges will be discussed, with a particular reference to distributional multimodality and integer-estimability of FDMA and LTE based carrier-phase systems.

Distributed computing: With data growth numerically straining conventional centralized approaches, complementary cooperative inferential capabilities are asked for. The opportunities of such principles are discussed and examples will be given of dividing estimation problems into easier-to-solve nodal problems which are then coordinated towards an improved, ideally optimal, solution by means of iterative schemes.

Predictive quality: As parameter estimation and statistical testing are typically combined in any geodetic inference, their interactions are to be taken into account when describing the quality of one’s model predictions. The challenges and intricacies that this brings are highlighted, whereby it is suggested that several of the existing validation and representation procedures need revisiting to ensure suitability of their quality descriptions.

How to cite: Teunissen, P.: Geodetic inference: a selection of some challenging topics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13344, https://doi.org/10.5194/egusphere-egu22-13344, 2022.

Atmospheric particulate plays an important role in air pollution and in the climate system.  There is a strong relationship between concentrations of fine particulate matter and increased morbidity and mortality and no threshold has been determined below which no detrimental health impacts have been detected.  This has led to World Health Organisation limit guidelines being revised to 5 μg/m³ for PM2.5, representing a major challenge since reduction on the scales required are very large indeed.  Aerosol particles scatter and absorb sunlight and influence cloud properties, and hence have an impact on climate through modification of regional radiation balance.  Understanding the chemical and physical properties of particulate is essential if we are to be able to discriminate different sources, determine the processes driving the additional of particulate mass as a result of atmospheric processing, and constrain the optical properties and influence atmospheric pathways that control regional radiative properties and distribution.

Over the last 20 years there has been a transformation in the capability of instrumentation capable of determining the composition of atmospheric particulate matter.  Offline analytical capability has enabled us to achieve a much more comprehensive molecular level description of aerosol composition.  Over the same period there has been a transformation in the capability of online instrumentation for measurements of aerosol composition.  Online mass spectrometric approaches now enable chemical characterisation of particulate at the molecular level in near-real time.  Optical methods are also providing insight into fine particles, for example determining black carbon properties.  Such measurements are providing an unprecedented insight into aerosol processes in the atmosphere on a wide range of scales and offer new observational constraints on many key atmospheric processes.

This presentation will examine the development of online aerosol measurement capability and its use in air quality and regional climate research, focussing on field observations, including observations from airborne platforms. The talk will consider the source contribution of vehicle, solid-fuel and cooking to primary aerosol in urban environments, and the contribution of secondary particulate matter and its sources, considering the role of both biogenic and anthropogenic precursors. Biomass-burning is a globally important source of both organic matter and black carbon and these sources are projected to increase as climate warms.  Observations have greatly advanced our knowledge of the relationship between biomass burning aerosol composition, optical properties and effect on radiation.  Airborne observations focusing on subtropical smoke across South America and Africa and links to radiative properties and effects on climate will be discussed.  The discussion will also cover secondary inorganic aerosol contributions from sulphur and nitrogen oxidation to aerosol and cloud properties. These observations have been used to provide constraint on global model estimates of aerosol budgets and lifecycles.  The presentation will outline future challenges for observational aerosol science in the atmosphere and the role of large observation platforms given the need to reduce carbon footprint.

How to cite: Coe, H.: Aerosol composition, climate and air quality, why molecular scale observations are important and what are the future challenges, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4229, https://doi.org/10.5194/egusphere-egu22-4229, 2022.

The past decades have seen significant increases in the societal and natural damages from extreme weather events. Preventing or limiting evitable future damages requires climate change mitigation and adaptation measures. Societal adaptation to changing weather and climate extremes requires detailed knowledge on how these meteorological extremes are changing (understanding future hazard) and knowledge of the pathways in which weather impacts society (understanding vulnerability and exposure).

A full focus on meteorology is therefore misguided, as the impact of two similar meteorological events at different times or different locations will vary widely. This shows the need for explicit consideration of the entire chain of events, and how this chain results in potentially heavy societal impacts. Developments in large ensemble climate modelling, data science and storyline techniques help to identify the meteorological drivers of extreme impacts.

We will illustrate these developments through practical examples for varied ‘impacts’, e.g. hydrological extremes, renewable energy extremes, and agricultural extremes. We will provide insights into the promise and pitfalls of modern big data approaches, and discuss ways forward, including co-production efforts to increase the societal uptake and hence usefulness of our science.

How to cite: van der Wiel, K.: Linking societal impacts to changing weather, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11953, https://doi.org/10.5194/egusphere-egu22-11953, 2022.

Atmospheric deposition of trace elements and nutrients to the ocean can significantly modify seawater chemistry and influence oceanic productivity.  However, mounting evidence suggests that the response of phytoplankton to atmospheric deposition depends on the chemical composition of the aerosols and varies across different phytoplankton species.  Responses are also different depending on oceanographic setting and season. To determine if and how nutrients, metals and other constituents from atmospheric deposition influence plankton activity and community structure in the ocean we analysed nutrient and metal concentrations in marine aerosols and tested how these constituents impact phytoplankton.  This is done using incubation experiments with natural phytoplankton assemblages and different sources and amounts of aerosol or pure nutrients and metal additions.  Variance in utilization of nutrients and susceptibility to metal toxicity was identified among different taxa, suggesting that aerosol deposition could potentially alter patterns of marine primary production and phytoplankton community structure.  In addition, input of bioaerosols can also affect phytoplankton communities and should be considered. Importantly, up to 25% of airborne microbes are viable upon deposition and may compete for resources with marine organisms. Airborne viruses can also infect specific phytoplankton hosts and hence impact the ecosystem. Natural and anthropogenic change could impact the chemical and biological composition of aerosols with consequences to ocean chemistry and productivity with potential feedbacks to the carbon cycle.

How to cite: Paytan, A.: Atmospheric Deposotion Impacts on Marine Biogeochemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-902, https://doi.org/10.5194/egusphere-egu22-902, 2022.

To fulfill the international objective “…to reach global peaking of greenhouse gas emissions as soon as possible … and to undertake rapid reductions thereafter in accordance with best available science...to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”, the Paris Agreement implemented the Global Stocktake Process to assess regularly the world’s collective progress towards achieving the purpose of the agreement and its long-term goals.

National greenhouse gas (GHG) inventories report only anthropogenic fluxes. However, many GHG sources are difficult to separate from the natural fluxes. Moreover, inventories cannot easily be scaled to the globe given the use of different approaches for GHG budgeting but, more importantly, because the states of the natural ocean and land sinks are not considered. Fast developments in the scientific capabilities to quantify GHG budgets and their trends consistently from the global to the national scale as well as accurate attribution of budgets to natural and anthropogenic processes are needed.

In Global Carbon Budgets top-down and bottom-up estimates still show large discrepancies at regional or country scale, due to large and multiple sources of uncertainty. Reducing these uncertainties and improving regional GHG budgets is currently the focus of the second “REgional Carbon Cycle Assessment and Processes” (RECCAP-2) initiative supported by the Global Carbon Project. This effort is fueled by an ever-expanding constellation of and in-situ and satellite-based GHG observations, and by increased process-based and data-driven modelling capabilities.

Here, I will discuss some of the elements that still challenge our ability to robustly link global to the regional and country carbon budgets, and their implications for the Global Stocktake. I will then show recent examples on how multi data-stream approaches can be used to identify and understand sources of discrepancies between top-down and bottom-up estimates and to improve attribution of regional carbon budgets to specific natural and anthropogenic processes.  

How to cite: Bastos, A.: Carbon budgets from global to regional scales: current challenges and future perspectives, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3435, https://doi.org/10.5194/egusphere-egu22-3435, 2022.

Due to their relevance for regional weather and climate, teleconnections are an extremely active area of research. One key task is to quantify the contribution of a teleconnection to regional anomalies in both models and observations. This is, for instance, important to improve forecasts on time scales ranging from subseasonal to multidecadal, or to attribute ensemble spreads to changes in large-scale drivers. However, robustly estimating the effects of a teleconnection remains challenging due to the often simultaneous influences of multiple climate modes. While physical knowledge about the involved mechanisms is often available, how to extract a particular causal pathway from data are usually unclear.

In this talk I argue for adopting a causal inference-based framework in the statistical analysis of teleconnections to overcome this challenge. A causal approach requires explicitly including expert knowledge in the statistical analysis, which allows one to draw quantitative conclusions. I illustrate some of the key concepts of this theory with simple examples of well-known atmospheric teleconnections. Moreover, I show how the deductive nature of a causal approach can help to assess the plausible influence of Arctic sea ice loss on mid-latitude winter weather, thereby helping to reconcile differences between models and observations. I finally discuss the particular challenges and advantages a causal inference-based approach implies for climate science.

References

Kretschmer, M., Adams, S. V., Arribas, A., Prudden, R., Robinson, N., Saggioro, E., & Shepherd, T. G. (2021). Quantifying Causal Pathways of Teleconnections, Bulletin of the American Meteorological Society, 102(12), E2247-E2263. Retrieved Jan 13, 2022, from https://journals.ametsoc.org/view/journals/bams/102/12/BAMS-D-20-0117.1.xml

Kretschmer, M., Zappa, G., and Shepherd, T. G. (2020), The role of Barents–Kara sea ice loss in projected polar vortex changes, Weather and Climate Dynamics, doi: 10.5194/wcd-1-715-2020

How to cite: Kretschmer, M.: Quantifying Causal Pathways of Teleconnections, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8246, https://doi.org/10.5194/egusphere-egu22-8246, 2022.

Understanding how the Earth’s shape, gravity field and rotation change in response to shifting hydrological, atmospherical and oceanic mass loads at its surface has great potential for monitoring the evolving climate. Recent advances in the field, namely hydrogeodesy, have required hand-in-hand development and improvement of the observing techniques and of our understanding of the solid Earth-climate interactions. 

In particular, measurement of the spatial and temporal variations of the Earth's gravity field by the GRACE and GRACE-Follow On satellite missions offer an unprecedented measurement of the evolution of water mass redistribution, at timescales ranging from months to decades. However, the use of GRACE and GRACE-FO data for hydrological applications presents two major difficulties. First, the mission design and data processing lead to measurement noise and errors that limit GRACE missions to large-scale applications and complicates geophysical interpretation. Moreover, temporal observational gaps, including the 11 month-long gap between missions, prevent the interpretation of long-term mass variations. Secondly, disentangling sources of signals from the solid Earth and continental hydrology is challenging and requires to develop methods benefiting from multiple geodetic techniques. 

To reduce noise and enhance geophysical signals in the data, we develop a method based on a spectral analysis by Multiple Singular Spectrum Analysis (M-SSA) which, using the spatio-temporal correlations of the GRACE-GRACE-FO time series, can fill observational gaps and remove a significant portion of the distinctive noise pattern while maintaining the best possible spatial resolution. This processing reveals hydrological signals that are less well or not resolved by other processing strategies. We discuss regional hydrological mass balance, including lakes, aquifers and ice caps regions, derived from the GRACE-GRACE-FO M-SSA solution. Furthermore, we discuss methods to separate sources of gravity variations using additional in-situ hydrological data or geodetic measurements of the Earth’s deformation. 

How to cite: Chanard, K.: Geodesy: a sensor for hydrology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12642, https://doi.org/10.5194/egusphere-egu22-12642, 2022.

Earthquakes provide a crucial way of probing the deformation style, strength, and stress state of the lithosphere.  In this talk, I will outline ways in which we can use careful analysis and precise seismological observations of earthquakes, particularly those at moderate magnitudes (M ~5-6), to map out how stress is supported in the lithosphere, and how the rheology of the lithosphere can vary in both space and time, summarising our current understanding of the controls on the distribution of earthquakes.  I will draw on examples from a range of regional studies, and outline what conclusions we can draw about the geological and geodynamic controls on the distribution of earthquakes in each region, and the variation on the style of deformation within the lithosphere.  I will also discuss areas in which our current understanding of the distribution of earthquakes remains unable to explain some observations, and challenges for the future.

How to cite: Craig, T.: Probing the rheology of the lithosphere using earthquake seismology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13373, https://doi.org/10.5194/egusphere-egu22-13373, 2022.

Hard engineering solutions are becoming economically unviable due to the high costs of construction, maintenance and adaptation to changes in sea level and storms. ‘Engineering with Nature’ (including the creation of salt marshes, seagrass beds) offers a more economically viable alternative for coastal protection.

However, despite the growing recognition of the necessity to move towards this greener alternative for coastal protection, there are still large uncertainties about factors determining the resilience of these systems to environmental change. As a consequence of sea-level rise, and of the increased occurrence of extreme weather conditions, coastal habitats are at risk of degradation and possible recession.  Human interactions add a layer of complexity to natural processes. Among the others, the sediment delivery to coastal areas has significantly changed over the years, for instance due to changes in catchment management, with consequences for the resilience of coastal systems.

This work uses numerical models to investigate the morphological and hydrodynamic features of coastal systems with environmental change. These numerical tools consist of hydrodynamic models coupled with morphological and sediment transport modules. Results investigate feedbacks between the shape of existing shorelines, wetlands resilience and external forcing such as tidal currents and wind waves. Results provide information useful for the study and management of ‘Engineering with Nature’ interventions and highlights the importance of a whole-system approach for the correct management of coastal areas.

How to cite: Leonardi, N.: Coastal wetlands and seagrass dynamics with environmental change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2798, https://doi.org/10.5194/egusphere-egu22-2798, 2022.

Sharp changes in lithology and increases in grain size and sedimentation rate of sedimentary sequences from tectonically active basins are often used to indicate regional neotectonic activity. However, these conventional methods have been challenged by others who argue that the sedimentary evidence used to infer tectonism could be climatically induced. Therefore, some forms of independent evidence or sedimentary criteria are required to discriminate between these two alternatives.

Seismites, sedimentary units preserved in subaqueous stratigraphic sequences that are caused by seismic shaking, are reliable indicators of regional tectonic activity. Subaqueous paleoseismology, can extend the record of strong earthquakes and augment the understanding of fault zone tectonic activity by studying seismites preserved in subaqueous sedimentary sequences. Here, we use the Dead Sea Basin (Middle East) and the Qaidam Basin (NE Tibet) as examples to further understand regional neotectonic activity from the perspectives of subaqueous paleoseismology.

The Dead Sea Basin is the deepest and largest continental tectonic structure in the world. In situ folded layers and intraclast breccia layer in the ICDP Core 5017-1 that recovered from the Dead Sea depocenter are identified as earthquake indicators, based on their resemblance to the lake outcrop observations of seismites that are known to be earthquake-induced. Based on the Kelvin-Helmholtz instability, we model the ground acceleration needed to produce each seismite by using the physical properties of the Dead Sea deposits. We invert acceleration for earthquake magnitude by considering regional earthquake ground motion attenuation, fault geometry, and other constraints.

Based on the magnitude constraints, we develop a 220 kyr-long record of Mw ≥7 earthquakes. The record shows a clustered earthquake recurrence pattern and a group-fault temporal clustering model, and reveals an unexpectedly high seismicity rate on a slow-slipping (~5 mm/yr) plate boundary. We also propose a new approach to establish the seismic origin of prehistoric turbidites that involves analyzing in situ deformation that underlies each turbidite. Moreover, our sedimentological data validate a long-lasting hypothesis that soft-sediment deformation in the Dead Sea formed at the sediment-water interface.

The Qaidam Basin is the largest topographic depression on the Tibetan Plateau that was formed by the ongoing India-Asia collision. The northeastward growth of Tibet formed a series of sub-parallel NW-SE-trending folds over a distance of ~300 km in the western Qaidam Basin. A long core was drilled in the basin on the crest of one such fold, the Jianshan Anticline. Sedimentological analysis reveals micro-faults, soft-sediment deformation, slumps, and detachment surfaces preserved in the core, which we interpret as paleoearthquake indicators. The core records five seismite clusters during 3.6-2.7 Ma. This suggests that the rate of tectonic strain accommodated by the folds/thrusts in the region varies in time and thus reveals episodic local deformation. During the clusters, regional deformation is concentrated more in the fold-and-thrust system than along regional major strike-slip faults.

This kind of research provides a fresh perspective for understanding regional tectonism by linking paleoseismic events and recurrence patterns with regional deformation, and can expand the ability of paleoseismology to understand the history of regional tectonics.

How to cite: Lu, Y., Waldmann, N., Wetzler, N., Moernaut, J., Bookman, R., Biasi, G. P., Strasser, M., Fang, X., Hubert-Ferrari, A., Alsop, G. I., Agnon, A., and Marco, S.: Subaqueous Paleoseismology: Fresh perspectives on sedimentary response to regional tectonics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1439, https://doi.org/10.5194/egusphere-egu22-1439, 2022.

The study of crustal stress examines the causes and consequences of in-situ stress in the Earth’s crust. Stress at any given point has several geological sources, including ‘short-term and local-scale’ and ‘long-term, ongoing and wide-scale’ source. In order to better characterise the crustal stress state, the analyses of both local- and wide-scale sources, and the consequences of their superposition are required. The global compilation of stress data in the World Stress Map database has increased significantly since its first release in 1992 and its analysis revealed large rotations of the stress tensor in several intraplate settings.

Large-scale stress analysis, so called first-order, (> 500 km) provides information on the key drivers of the stress state that result from large density contrasts and plate boundary forces. The analyses of stress at smaller-scales (< 500 km) have numerous applications in reservoir geomechanics, geo-storage sites, civil engineering and mining industry. To date, numerous studies have investigated the stress analysis from different perspectives. However, the stress, in geosciences, is still enigmatic because it is a scale-dependant parameter. It means, stress variations can be studied at both the ‘spatial-scale’ and ‘temporal-scale’. This paper aims to investigate the crustal stress pattern with a particular emphasis on the orientation of maximum horizontal stresses at various spatial-scales, ranging from continental scales down to basin, field and wellbore scales, to better evaluate the role of various stress sources and their applications in the Earth’s crust. The stress analyses conducted in this work shows that stress pattern at large-scales do not necessarily represent the in-situ stress pattern at smaller-scales. Similarly, analysis of just a couple of borehole measurements in one area might not yield a good representation of the regional stress pattern.

How to cite: Rajabi, M. and Heidbach, O.: Crustal stress across spatial scales, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12964, https://doi.org/10.5194/egusphere-egu22-12964, 2022.

Landslides are prevalent in mountain landscapes and interact with the river network in a myriad of ways with impacts on flood and debris flow hazards and landscape evolution. Floods in mountainous regions often coincide with a high density of landslides triggered by heavy rainfall. However, the impacts of landslide-delivered sediment on flood dynamics are not typically considered in flood hazard assessment. Higher up in the river network, landslide sediment supply is a key component of debris flows. Yet, assessments of climate change impacts on debris flows to date have focused on likely changes in rainfall triggering potential of debris flows, overlooking the role of landslide sediment supply.

In a first case study, I demonstrate with an example from the Colorado Front Range how landslide-channel feedbacks can significantly amplify channel erosion and flood risk. We used a combination of field analysis and modelling with a multiphase flow model R.avaflow to test the hypotheses that landslide-flood interactions amplified channel erosion during a major flood event in 2013 by (1) bulking of the flow and (2) dam formation and failure dynamics.

In a second case study, I demonstrate with an example from the Swiss Alps, how landslide sediment supply limits debris flow hazard in a warming climate. We forced the sediment cascade model, SedCas, with climate simulations to disentangle the interactions between hydrological triggering, landslide sediment supply and elevation on mountain basin sediment transfer and debris flow hazard over the 21^st century. 

How to cite: Bennett, G.: Accounting for landslide-channel interactions in landscape evolution and hazards, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4290, https://doi.org/10.5194/egusphere-egu22-4290, 2022.