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

How to cite: Fu, B.: Coupling Human - Earth Systems for Sustainability, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2798, https://doi.org/10.5194/egusphere-egu2020-2798, 2020.

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

How to cite: Levin, I.: Radiocarbon in modern Carbon Cycle research, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1943, https://doi.org/10.5194/egusphere-egu2020-1943, 2020.

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

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

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

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

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

Experimental volcanology has a rich future...  

How to cite: Dingwell, D. B.: Experimental Access to Volcanic Processes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2053, https://doi.org/10.5194/egusphere-egu2020-2053, 2020.

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

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

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

How to cite: Ehrenfreund, P.: Organic chemistry in space and the search for life in our Solar System, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10885, https://doi.org/10.5194/egusphere-egu2020-10885, 2020.

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

How to cite: Cobb, K. M.: Paleoclimate science for the 21st century: a wishlist, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22684, https://doi.org/10.5194/egusphere-egu2020-22684, 2020.

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

How to cite: Sanchez-Vila, X.: Porous media as a canvas for hydro-bio-geo-chemical processes: Facing the challenges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1435, https://doi.org/10.5194/egusphere-egu2020-1435, 2020.

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

How to cite: Wessel, P.: The Generic Mapping Tools and Community-Maintained Open Source Software, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2245, https://doi.org/10.5194/egusphere-egu2020-2245, 2020.

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

How to cite: Porporato, A.: Hydrology without Dimensions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11883, https://doi.org/10.5194/egusphere-egu2020-11883, 2020.

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

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

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

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

How to cite: Zhu, W., Xing, T., Kanaya, T., Zega, Z., and French, M.: Mechanisms for Pore Fluid Stabilization of Fault Propagation and Slip, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11918, https://doi.org/10.5194/egusphere-egu2020-11918, 2020.

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

How to cite: Zhu, R.: Early human occupation in mainland East Asia: Implication for climate change and human evolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12194, https://doi.org/10.5194/egusphere-egu2020-12194, 2020.

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

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

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

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

How to cite: Guggenberger, G., Liebmann, P., Wordell-Dietrich, P., Preußer, S., Kalks, F., Leinemann, T., Cerli, C., Kandeler, E., Don, A., Mikutta, R., and Kalbitz, K.: Dynamic exchange and remobilization processes as controls of soil organic carbon turnover, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19907, https://doi.org/10.5194/egusphere-egu2020-19907, 2020.

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

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

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

How to cite: Coulthard, T.: Geomorphic Apophenia: Inferring meaning where there could be none?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22691, https://doi.org/10.5194/egusphere-egu2020-22691, 2020.

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

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

We particularly focus the attention on inverse problems of Geodesy and multiscale mollifier regularization strategies. Two examples are studied in more detail:

(i) Vening Meinesz multiscale surface mollifier regularization to determine locally the Earth's disturbing potential from deflections of vertical,

(ii) Newton multiscale volume mollifier regularization of the inverse gravimetry problem to derive locally the density contrast distribution from functionals of the Newton integral and to detect fine particulars of geological relevance.

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

How to cite: Freeden, W.: Geodesy and Mathematics: Interactions in Multiscale Mollifier Regularization Methods, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3650, https://doi.org/10.5194/egusphere-egu2020-3650, 2020.

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

How to cite: Gibney, E.: From black holes to Brexit: the inside track on science journalism, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22693, https://doi.org/10.5194/egusphere-egu2020-22693, 2020.