EGU General Assembly 2023  

Soil hydrological processes play an important role in the Earth System. As part of the Critical Zone, they support ecosystem services, modulate the impact of climate change on terrestrial systems and control feedback mechanisms between water, energy and biogeochemical cycles. They act at multiple scales, ranging from the pore scale to the continental scale. Despite the fact, that the first meters of the critical zone only store a small amount of water, about 60% of the terrestrial rainfall is being transpired by plants through the root zone or evaporated by the soil, the remaining part is mainly diverted into groundwater recharge and runoff. This lecture will address some of the current challenges that hydrological research of soils and the critical zone face. These include the high nonlinearity in soil hydrological processes, the multi-scale heterogeneity in hydraulic properties, the provision of hydraulic parameters across scales, the role of soil structural properties and improving rhizosphere process descriptions. Finally, the importance of observing hydrological states and fluxes and their role in understanding and predicting soil hydrological processes will be addressed.

How to cite: Vereecken, H.: On the hydrology of soils in the Earth System, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1156, https://doi.org/10.5194/egusphere-egu23-1156, 2023.

Plate divergence at mid-ocean ridges results from a combination of three main processes: magma emplacement, faulting and hydrothermalism. Melt fluxes at fast and most intermediate spreading ridges are high enough that the axial lithosphere (the plate between the plates) remains thin, or at least thinner than the cumulative melt thickness (melt flux divided by expansion rate) per unit length of ridge. In this configuration, the magma can fully accommodate plate divergence. This is not the case for slow and ultraslow ridges, where melt fluxes are lower, resulting in colder axial geotherms and an axial lithosphere that is in the general case thicker than the cumulative melt thickness per km of ridge. In this configuration, faults must accommodate a significant part of plate divergence, while magma may be emplaced at a range of depths, over the full thickness of the axial plate. This creates the conditions for the common exhumation of mantle-derived peridotites and the formation of a composite (variably serpentinized peridotites and magmatic rocks) oceanic crust. Melt fluxes, and probably melt emplacement depths, are also highly variable at slow-ultraslow ridges. This allows for complex interactions between magma and faults, and between magma and hydrothermal circulation, resulting in spatially and temporaly variable spreading modes (the combination of the mid-ocean ridge tectonic, magmatic and hydrothermal processes that determine the composition and structure of the oceanic lithosphere). In this presentation, I revisit these concepts, discuss the extent to which they have been tested by experiments and modelling, and point to several remaining questions.

How to cite: Cannat, M.: Magma fluxes and magma emplacement depths are key to understanding the modes of plate divergence at slow and ultraslow spreading mid-ocean ridges, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14273, https://doi.org/10.5194/egusphere-egu23-14273, 2023.

Some of the satellites of the gas giants Jupiter and Saturn, at orbits beyond the snow-line and the traditional “habitable zone”, have been revealed by missions like Galileo, Cassini-Huygens and Juno as unique and extremely interesting bodies with a strong astrobiological potential [1]. Jupiter’s Europa and Ganymede show indications of harboring liquid water oceans under their icy crusts, which, in the case of Europa, may be in direct contact with a silicate mantle floor and kept warm through time by tidally generated heat. Ganymede, the largest satellite in our Solar System, is unique in possessing an induced magnetic field and probably harbours an undersurface liquid water ocean contained between two ice layers. Thanks to the fabulous international cooperation that came behind the Cassini-Huygens mission, Saturn’s system was revealed and Titan [2] and Enceladus [3], were found to possess organic chemistry, unique geological features and internal liquid water oceans. I will describe my personal experience of the Cassini-Huygens mission.

The icy satellites provide a conceptual basis within which new theories for understanding habitability can be constructed. In view of the many questions remaining unanswered [4], these bodies will be further investigated in the future by new missions to the giant planets systems. Future space exploration towards the Galilean satellites will be performed by missions such as ESA’s JUpiter Icy moons Explorer (JUICE, [5]) (whose main target is Ganymede and will be launched in April 2023) and NASA’s Europa Clipper mission to launch in 2024. For a return to Titan, NASA has recently selected the Dragonfly mission [6], while other concepts are being studied for these and other icy moons, also around the ice giants.

Future in situ measurements will be extremely useful in unveiling these worlds. In the meantime, Juno data and ground-based observations can help complement the space discoveries.

I will discuss what we currently know and what we expect to learn about habitable conditions in the outer solar system and how our perception of these worlds has changed, along with the need to better protect their environments [7].

References:

• 1. Coustenis, A., Encrenaz, Th., 2013. Life beyond Earth: the search for habitable worlds in the Universe. CUP. ISBN: 9781107026179.
• 2. Coustenis, A., 2021. The Atmosphere of Titan. In Read, P. (Ed.), Oxford Research Encyclopedia of Planetary Science.  DOI: 10.1093/acrefore/9780190647926.013.120
• 3. Lunine, J., Coustenis, A., Mitri, G., et al., 2018. “Future exploration of Enceladus and other Saturnian moons”. In “Enceladus and the Icy Moons of Saturn”. LPI/UA/Space Science Series, P. Schenk, R. Clark, C.J.A. Howett, A. Verbiscer, J.H. Waite Eds., ISBN 9780816537075.
• 4. Nixon, C. A., et al., 2018. PSS, 155, 50-72.
• 5. Coustenis, A., Witasse, O., Erd, C., 2021. The JUICE mission: expectations and challenges. Fall issue of The Bridge on space exploration, Sept. 2021, Vol. 51, issue #3, pp. 41-50. https://www.nae.edu/260902/The-JUICE-Mission-Challenges-and-Expectations
• 6. Barnes, J. et al., The Plan. Sci. J., 4, 18.
• 7. Fisk, L., Worms, J.-C., Coustenis, A., et al., 2021. Introductory Note to the June 2021 and Update of the COSPAR Policy on Planetary Protection. Space Research Today 211, Aug. 2021, 9-25, https://doi.org/10.1016/j.srt.2021.07.009 and Policy : https://doi.org/10.1016/j.srt.2021.07.010

How to cite: Coustenis, A.: Habitable conditions in the outer solar system : the space missions that changed our perception of what exists out there, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1912, https://doi.org/10.5194/egusphere-egu23-1912, 2023.

Under continued global warming, extreme events such as heatwaves will continue to rise in frequency, intensity, duration, and spatial extent over the next decades. Younger generations are therefore expected to face more such events across their lifetimes compared to older generations. This raises important questions about solidarity and fairness across generations that have fuelled a surge of climate protests led by young people in recent years, and that underpin questions of intergenerational equity raised in recent climate litigation. However, scientific analyses that explicitly consider the intergenerational equity dimension of the climate crisis are remarkably absent. Our standard scientific paradigm is to assess climate change in discrete time windows or at discrete levels of warming, a “period” approach that inhibits quantification of how much more extreme events a particular generation will experience over its lifetime compared to another. By developing a “cohort” perspective to quantify changes in lifetime exposure to climate extremes and compare across generations, we estimate that children born in 2020 will experience a two to sevenfold increase in extreme events, relative to the 1960 birth cohort, under current climate pledges. Building on this framework, we quantify where and when people start living an unprecedented life, as well as intergenerational differences in exposure to attributable extreme events. Furthermore, using a new water deficit indicator, we uncover spatiotemporal differences in lifetime water scarcity. Our results overall highlight a severe threat to the safety of young generations and call for drastic emission reductions to safeguard their future. Finally, this research is already being used in ongoing litigation (e.g. Duarte Agostinho and Others v. Portugal and 32 Other States), calling for more research in this direction to bolster the upcoming wave of climate lawsuits.

How to cite: Thiery, W.: The kids aren’t alright, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12474, https://doi.org/10.5194/egusphere-egu23-12474, 2023.

The progressive localization of deformation has long been recognized as a fundamental phenomenon of the macroscopic failure of rocks. Our recent analyses using X-ray tomography during triaxial compression indicate that fractures and higher magnitudes of shear and dilative strain spatially localize as rocks are driven closer to macroscopic failure. Similarly, geophysical observations of low magnitude seismicity in southern and Baja California show that deformation localizes toward the future rupture plane of M>7 earthquakes. These sets of observations indicate that deformation can increase in localization toward failure, and that deformation can temporarily decrease in localization (delocalize) during this overall increase. These observations indicate that the spatial organization of deformation may be used to recognize the acceleration of the precursory phase leading to large earthquakes and the macroscopic, system-scale failure of heterogeneous materials. However, such efforts will require identifying the conditions that promote phases of delocalization, and how these perturbations in the overall trend of increasing localization influence the timing of macroscopic failure. In this presentation, I will describe these analyses, and new work that aims to identify which characteristics of the fracture networks determine the localization at a particular level of stress, and the change in localization from one stress step to the next in triaxial compression experiments at the confining stress conditions of the upper crust.

How to cite: McBeck, J., Renard, F., and Ben-Zion, Y.: Episodic delocalization in the upper crust: Implications for earthquake forecasting, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1798, https://doi.org/10.5194/egusphere-egu23-1798, 2023.

Martian gullies are kilometre-scale landforms consisting of an alcove, channel and depositional fan. They are among the youngest landforms that may have formed by liquid water and are active today. Understanding their formation is thus critical for resolving Mars’ most recent climatic history and potential to sustain life. Gullies on Mars have been hypothesized to have formed by either the action of liquid water and brines or the action of sublimating carbon-dioxide (CO₂) ice. They strongly resemble terrestrial systems formed by aqueous debris flows, having similar sedimentology, morphology, and morphometry. Yet, new deposits have formed within multiple gullies across Mars over the past decade, and we cannot reconcile these flows with the low availability of atmospheric water and the triple point of water under present martian conditions. These flows do, however, occur in winter when temperatures are below the CO₂ condensation point, and CO₂-ice has been observed in many gullies during time of activity. But can CO₂ sublimation support and fluidize mass flow on Mars and form deposits similar to terrestrial debris flows? Here, I present novel experiments where we operate small-scale mass-flow flumes inside Mars chambers at Aarhus University (Denmark) and the Open University (UK). In these chambers Martian atmospheric conditions can be simulated, which is crucial for fluidization of mass flows since volume expansion, and therefore gas flow rate, by CO₂-ice sublimation is much larger under the low atmospheric pressure of Mars (8 mbar) than under the atmospheric pressure of Earth (1000 mbar). These experiments reveal that CO₂ sublimation under martian atmospheric conditions can fluidize mass flows by generating elevated pore pressures reducing intergranular friction, resulting in lobate deposits with levees, as observed in martian gullies. These findings show that CO₂-sublimation processes can explain our observations in active Martian gully systems today, which has far-reaching implications for the search for potential liquid water on Mars as well as the interpretation of planetary landforms on other planetary bodies. In particular, they show that on planetary bodies unlike Earth, landforms may be created that look similar to those found on Earth but are actually produced by disparate and so-far unknown processes.

How to cite: de Haas, T., Roelofs, L., Conway, S., McElwaine, J., Merrison, J., Patel, M., and Sylvest, M.: Sublimation-driven formation of recent mass flows on Mars: experimental tests in low-pressure environments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1451, https://doi.org/10.5194/egusphere-egu23-1451, 2023.

I joined the British Broadcasting Corporation (BBC) as a 22-year-old radio reporter in the city of Cambridge, in the east of England. At the time, I had the intention of becoming another John Cole, the late, great political editor of the BBC. Politics and social issues were what fascinated me. But a chance meeting one spring afternoon with a scientist at the city’s famous Laboratory of Molecular Biology changed the direction of my career. I was stunned by what this man had achieved (he would later win a Chemistry Nobel) and committed to becoming a journalist specialising in the reporting of science. This was problematic as I’d had no real science education at school. But seven years with the Open University as a mature student put that right, and in 1998 I found myself in the position of leading the science coverage on the fledgling BBC News website. I’ve been a full-time science hack ever since. When I started in journalism my tools were a reel-to-reel recorder, a typewriter and several sheets of carbon copy paper to produce my radio scripts in duplicate. Today, as I approach the end of my career, I operate in a fully digital newsroom with mp3 recorders, cloud computing and AI. My medal lecture will detail the journey from the old to the new. I will pass on some of the lessons learned (which should be of interest to those wanting to interact with journalists) and consider some of the challenges ahead for my profession.

How to cite: Amos, J. C. D. A.: From carbon copy paper to AI: 36 years as a reporter for the BBC, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17598, https://doi.org/10.5194/egusphere-egu23-17598, 2023.

Science communication exists on a spectrum: from dissemination to dialogue. While participation is likely to be the most effective way of helping to truly diversify science, there is still a need for geoscience communication initiatives that exist across this spectrum. In this Katia and Maurice Krafft Award lecture I will present an overview of my research into using poetry and games as facilitatory media to help disseminate knowledge, develop dialogue between scientists and non-scientists, and engender participation amongst diverse publics, including those audiences that have previously been marginalised by the geosciences.

By presenting a series of case studies, published works, and works in progress, I aim to demonstrate how this creative approach can help to address a lack of diversity in the geosciences. This lack of diversity should be paramount to anyone who is involved in either the geosciences or geoscience communication, not only because it is ethically the ‘right thing’ to do, but because ultimately greater diversity results in better science.

In addition to my own research, I will also explore how the work that we are doing with the EGU journal Geoscience Communication is supporting others in developing innovative and effective research and practice in this space, and how this in turn is helping to provide greater recognition for science communication in the geosciences.

How to cite: Illingworth, S.: From Dissemination to Participation – A Creative Approach to Geoscience Communication, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3055, https://doi.org/10.5194/egusphere-egu23-3055, 2023.

As the global population expands, the demand for food, fuel and fiber rises steadily. Meeting these needs in a sustainable manner, without depleting natural resources or polluting the environment remains one of the greatest challenges of our time. What is more, anticipating changes in these systems as a result of climate change, and across a multitude of environmental and socioeconomic contexts adds yet even further complexity to this already convoluted issue. 

At the heart of this matter lies agricultural soils, and how management practices are used to modify and adapt their capacity to sequester carbon and provide nutrients and water to growing plants. While soils are notoriously heterogenous on their own, this is further enhanced by their role as an important environmental reservoir linking plants and residues to soil microbial communities and soil fauna, the atmosphere, and water. Understanding how management practices influence these interactive aspects of the soil environment is key to developing agricultural management systems in a sustainable, effective and site-specific manner.

In this presentation I will highlight how it is vital for future studies to consider a) how management practices will simultaneously impact a variety of different soil functions or services, not just one or two, in order to assess environmental tradeoffs within a given system, b) how these are impacted across different spatial scales, and c) the importance of developing management practices that are adapted to local, site-specific conditions. It is clear that the complexity of modifying agricultural systems to survive in a rapidly changing climate demands interdisciplinary approaches. It is thus my hope that this presentation will foster open discussion and meaningful collaborations to address such challenging societal questions.

How to cite: Garland, G.: Sustainable management of agricultural soils: Balancing multiple perspectives and tradeoffs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2801, https://doi.org/10.5194/egusphere-egu23-2801, 2023.

Introduction: Contamination causes undue risks to society, ecosystems, water and soil resources, and threatens the viability of many industries^1,2. As well as affecting soil, surface water and groundwater, air pollution has been recognised as one of the planet’s most challenging problems. This contamination of the living environment has been linked to 13.7 million deaths a year by the World Health Organisation, almost a quarter of all human fatalities https://www.who.int/data/gho/data/themes/public-health-and-environment). Even more concerning are the nonlethal side effects of global contamination, e.g. the decline in human IQ, the collapse of male fertility, the increase in child developmental and mental disorders etc. which, on a daily basis, adds millions of dollars to medical costs and indeed impacts the quality of human life. Describing contamination’s impact by deaths alone understates the problem. It is the lifelong disabilities and suffering of a growing percentage of the population which is also a core issue. There are hardly any measures in place to minimise these impacts other than some regulatory measures that rarely include all toxins in circulation around the planet.

The extent and severity of air pollution depends on many factors – including population, industrial activities, and measures in place to minimise contamination – and thus varies considerably among and within countries. Although more than $US$2 billion is spent annually to manage or remediate contaminated land and water bodies in Australia, limited funds have been allocated towards the management or remediation of air. Globally, environmental management costs exceed $US750 billion per annum with US $65 to $85 billion of this used for clean-up costs. However, these costs do not include the medical costs linked to many debilitating human health issues confronted in most if not all countries globally.

Globally, it is estimated that there are more than 10 million potentially contaminated sites. Despite growing awareness of the risks of exposure to contaminants, activities that contribute to contamination of our environment are on the increase in many countries as populations grow and industrialisation increases. One reason for this is a lack of adherence to regulatory policies, especially in developing countries, many of which are chronically under-resourced. What is needed are global protocols for restricting the use of toxic chemicals and a global 'contamination IPCC' to oversee and reduce universal contamination. Take a metaphor of IPCC that the climate talk and action has been much visible as a result of forming Intergovernmental Panel on Climate Change (IPCC) in 1988.

The proportion of contaminated sites that are successfully remediated is disconcertingly small. Uncertainties about the nature and extent of contamination can be a major constraint to sustainable development in both urban and rural areas, thereby increasing pressure on the use of limited uncontaminated land. Moreover, many techniques available for in situ or ex situ remediation are prohibitively expensive and thus poorly adopted.¹

Unlike point source contamination associated with industrial activities, diffuse pollution, such as that encountered in broadacre or agricultural farmlands, poses a different challenge. Although the risk of direct exposure from soil to person is low, the bioaccumulation of contaminants into crops and subsequent exposure via food consumption poses a major risk to humans and also damages local and international trade. Added to these are the inherent dangers of chemical mixtures, even from innocuous substances. The dangers of chemical mixtures are rarely considered by regulatory jurisdictions and indeed industries linked to contaminants. Also, the absence of information about the toxicity of new and existing chemicals further constrains management of environmental contamination.

Although generally present in low concentrations, diffuse contamination is often difficult and expensive to remediate because it can be spread over very large areas.

Exposure risks: The risks associated with exposure to contaminants vary considerably depending on the source and pollutant matrix. While 4 million deaths per year are linked to soil, water or food contamination, a recent World Health Organization report estimates air pollution poses a much higher risk than other forms of pollution, killing an estimated 6 million people every year. UK estimates suggest that air pollution will make 2.4 million people ill in England between now and 2035 and the healthcare and social costs of air pollution could reach US $23 billion by 2035.3 Air pollution is now seen as the invisible killer. Air pollution is caused almost entirely due to the use of fossil fuels and is expected to decline as they are phased out. Furthermore, environmental management is constrained by the highly leachable nature of soils in countries with sub-humid to humid tropical conditions (compared to soils in USA and Europe), and this limits application of technologies developed elsewhere. To make sound risk and remediation decisions, we need to refine the way we assess risks from contaminants. We need improved data and protocols that provide reliable prediction of exposures and the associated human/eco-impacts. We also need improved monitoring and assessment procedures and instrumentation for contaminants to deliver reliable, accurate data on contaminant presence and fate.

Clean up: The cost of clean-up continues to rise given the challenges of remediating both surface and subsurface contamination. Soil is now seen as a complex heterogeneous system that, once contaminated (especially when coupled with groundwater), is not easily remediated. Furthermore, drastic risk control (e.g. cleaning up sites to background concentrations or to the levels suitable for sensitive land use) is rarely technically or economically feasible. It is thus desirable to apply remedial approaches that reduce the risk of contamination while allowing the soil to remain on site. This approach to site remediation, which is gaining increasing acceptance, is commonly known as risk-based land management.

While clean-up is desirable it does not address and will never solve the overall contamination problem. It treats only one of the symptoms. What is needed is a global treaty to reduce Earth system contamination at source – i.e. to prevent pollution occurring in the first place by not releasing any more untested chemicals, maintaining a global inventory of what is released, and pinpointing major sources of toxicity (e.g. plastics in the home).

While the act of contaminating the environment may itself expend low energy and cost, the complex nature of contaminants – coupled with the heterogeneity of media in which contamination resides, risks and multiple receptors – means that the act of cleaning up is complex and cost- and energy-intensive. Given our planet’s large number of contaminated sites, the fragmented approach along national lines and the slow pace of remediation, it will take many generations to clean up the Earth, and we will never achieve the pristine conditions that existed prior to human civilisation.

Can we clean up the earth? This paper has provided an overview of the extent of global contamination, its risks and impacts, the challenges to remediation, and why a clean Earth is humanity’s next great challenge. The paper has also proposed that an international ‘contamination IPCC’ is necessary to meet this challenge. An international body of this type could champion a coordinated approach to the following issues.

Global issues that need to be considered:
(a)    The development of a comprehensive database and international chemical inventory and improved exposure pathway models that would assist with risk assessment of contaminated sites and air pollution.
(b)    The prioritisation of action for target contaminants/circumstances, especially for recalcitrant contaminants and mixtures in complex environments or where high risks are posed.
(c)    The development of specific remediation techniques relevant to region- or country-specific conditions, and demonstration of those techniques at national scale to encourage uptake.
(d)    The development of a database that provides the basis for a decision-support system on techniques for remediation or management of contaminated sites.
(e)    The availability of highly qualified environmental management and risk assessment graduates.
(f)    Environmental legislators with expertise in assessment and management of site contamination.
(g)    Trained professionals who can assist with the social implications of contaminants.
(h)    A global industry training program to raise industry awareness of the effects of global poisoning (which they ignore) and build a culture of stewardship for dangerous products.

Capacity building: Addressing the issues outlined above will also require a significant effort to build sufficient skilled capacity around the globe. There is strong demand for trained graduates with expertise in not only environmental management but also legal and social issues relating to contaminated soils.

Conclusion: The large number of contaminated sites together with increasing evidence of health effects from the consumption of foods grown on contaminated sites or farms with low level of contamination suggests that there would be considerable benefit in assembling a focussed group of international leaders in the field – through mechanisms such as the globalCARE™ initiative – to tackle these problems on a global scale. Members of this group should have skills to develop technology for (a) assessment of risks, and (b) management or remediation of degraded environments contaminated from both point and dispersed sources. A well-resourced international group such as this, together with a global treaty to reduce contamination at its source, may be able to reverse the trend and in time may well be able clean up the earth.

References

1.    Naidu, R. (2013). Recent Advances in Contaminated Site Remediation. Water, Air, and Soil Pollution. 224(12), 1705.
2.    Naidu, R. et al. (2021). Chemical pollution: A growing peril and potential catastrophic risk to humanity. Environment International. 156, 106616.
3.    Kass, D. (2018). Air pollution kills six million people every year: it's time for us to wake up to this grave threat. The Telegraph, 27 September 2018. www.telegraph.co.uk/news/2018/09/27/air-pollution-kills-six-million-people-every-year-time-us-wake/ 

How to cite: Naidu, R.: Can we clean up the earth?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17578, https://doi.org/10.5194/egusphere-egu23-17578, 2023.

Plate tectonics is the surface expression of mantle convection, but many aspects of our present-day tectonic setting depend on how the solid Earth system has evolved over time. I touch on work across a range of spatio-temporal scales addressing how convective memory can be used to validate tectonic scenarios to better understand plate boundary evolution. Seismic anisotropy in the upper mantle is one recorder of convective deformation, and the duration over which textures are reworked controls the lifespan of memory. This means that the lithosphere may allow distinguishing between different plate tectonic scenarios over the last ~50 Ma. Uncertainties about those scenarios and slab rheology imply that our understanding of subduction mass transport remains incomplete, leading to ambiguities about the deep mantle record of subduction. One particular issue is how slabs are deformed upon bending in the trench. I discuss results from convection models with rheological memory which affects subduction dynamics and plume-slab interactions. Within global, plate generating convection models, reactivation of damage zones increases the frequency of plate reorganizations, and hence reduces the dominant periods of surface heat loss fluctuations. Inheritance of lithospheric damage dominates surface tectonics over any local boundary stabilizing effects of rheological weakening. Progressive generation of weak zones may counteract any effects of reduced convective vigor throughout planetary cooling, with implications for the frequency of orogeny throughout Wilson cycles. I close by a consideration of the effects of local rheological damage weakening vs. the longest recorder of geological history of all, the continental lithosphere.

How to cite: Becker, T.: On convective memory, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3978, https://doi.org/10.5194/egusphere-egu23-3978, 2023.

When cold and dense oceanic lithosphere sinks into the mantle at subduction zones, it pushes weaker asthenospheric mantle away, creating specific flow patterns. Traditionally mantle flow is divided into two components: trench-perpendicular poloidal flow operating in a vertical plane and 3D toroidal flow around the slab edges. In the past years, we have learned that both poloidal and toroidal mantle flow around slabs effectively connects nearby subduction zones, deforming their slabs and upper plates, and modifying their patterns of volcanism and uplift/subsidence. In turn, the two-way dynamic interaction between the subduction zones also affects the flow pattern, and thus impacts the volcanism, surface uplift and lithospheric deformation (Király et al., 2021).

At present, our best constraints on mantle flow patterns around subduction zones originate from seismic anisotropy observations, which can be interpreted based on 3D geodynamic models. In the mantle, seismic anisotropy originates from crystallographic preferred orientation (CPO), which derives from the anisotropic nature of olivine crystals. Due to olivine’s orthorhombic symmetry and the different strengths of its three slip systems, olivine crystals are anisotropic in their elastic and viscous properties. Hence, when many olivine crystals are aligned within mantle rock (i.e., CPO is developed in an area of the mantle), the mantle will deform anisotropically, both for seismic wave transmission and viscous flow. Since CPO occurs as a response to deformation, seismic anisotropy directions are often read as the recent mantle flow direction in an area. However, there are a few complications to this simple one-to-one interpretation. First, because the CPO depends on the deformation history of the mantle, it might not reflect the current flow orientation if the deformation direction has changed through time (Ribe, 1989). Second, CPO formation depends on stress and on water content (Korenaga and Karato, 2008), which in some cases allows texture to form with a fast axis perpendicular to the deformation direction. Third, the interpretation of seismic anomalies is often difficult because geodynamic models do not incorporate enough complexity to model all the intricacies of the flow. This problem can occur due to complex anisotropic signals from crustal layers, from more complicated geodynamic settings (e.g., multiple slabs), or from a modified flow pattern that arises due to the viscous anisotropy associated with the texture itself.

In this presentation, I will use the Mediterranean area to highlight how including multiple slabs and accounting for viscous anisotropy can eventually help us to interpret the seismic observations from this geodynamically complex region.

References:

Király, Á., Funiciello, F., Capitanio, F.A., and Faccenna, C., 2021, Dynamic interactions between subduction zones: Global and Planetary Change, p. 103501, doi:10.1016/j.gloplacha.2021.103501.

Korenaga, J., and Karato, S., 2008, A new analysis of experimental data on olivine rheology: Journal of Geophysical Research, v. 113, p. 1–23, doi:10.1029/2007JB005100.

Ribe, N.M., 1989, Seismic Anisotropy and Mantle Flow: Journal of Geophysical Research, v. 94, p. 4213–4223.

How to cite: Király, Á.: Mantle flow around subduction zones: evolution through time, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9109, https://doi.org/10.5194/egusphere-egu23-9109, 2023.

It is theoretically demonstrated  that, even with perfectly complete and perfectly accurate data, there is a fundamental ambiguity in the analysis of potential field data. The ambiguity may be easily illustrated by computing some of the various kinds of structures that can give rise to the same anomaly field. To solve the ambiguity and yield reasonable geophysical models we must therefore supply a priori information. In gravimetry, the ambiguity comes from the fact that only the excess mass is uniquely determined by the anomaly, neither the density nor the source volume. However, not only the excess mass can be uniquely estimated. Examples are the center of a uniformly dense (or magnetized) sphere or the top of a deeply extended homogeneously-dense cylinder. A priori information may consist of direct information (e.g., depth, shape) and/or of assuming that the source distribution has some specified properties (e.g., compactness, positivity). If one tries to classify the physical source-distributions in terms of their complexity, we may however use two different scaling laws, based on homogeneity and self-similarity, which allow modeling of the Earth in its complex heterogeneity. While monofractals or homogeneous functions are scaling functions, that is they do not have a specific scale of interest, multi-fractal and multi-homogeneous models need to be described within a multiscale dataset. Thus, specific techniques are needed to manage the information contained on the whole multiscale dataset. In particular,  any potential field  generated by a complex source may be modeled as  a multi-homogeneous field, which typically present a fractional and spatially varying homogeneity degree. For a source of irregular shape, it may be convenient to invert not the  field but a related quantity, the scaling function, which is a multiscale function having the advantage of not involving the density among the unknown parameters. For density or magnetic susceptibility tomographies, the degree of spatially variable homogeneity can be incorporated in the model weighting function, which, in this way, does not require prior assumptions because it is entirely deductible from the data. We discover that difficult quantities, such as the bottom of the sources, or multiple source systems are reasonably well estimated by abandoning the analysis at a single scale and unraveling the scale-related complexity of geophysical signals. The inherent self-consistency of these new multiscale tools is a significant step forward, especially in the analysis of areas where there is scarce other information about the sources.

How to cite: Fedi, M.: Solving the ambiguity in the potential field exploration of complex sources, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13597, https://doi.org/10.5194/egusphere-egu23-13597, 2023.

The North Atlantic exhibits temperature variations on multidecadal time scales, summarized as the Atlantic Multidecadal Variability (AMV). The AMV plays an essential role in regional climate and is a crucial driver of the low-frequency variability in Northern Europe.

In this talk, I will first discuss the characteristic ocean-atmosphere interaction preceding an AMV maximum event. In the following, I will disentangle the seasonal impact of the AMV and show that a significant fraction of the variability in Baltic Sea winter temperatures is related to the AMV. The strong winter response can be linked to the interaction between the North Atlantic Oscillation, the Atlantic Meridional Overturning Circulation (AMOC), and the AMV. In contrast, the AMVs' impact on other seasons remains small.

How to cite: Börgel, F., Meier, H. E. M., Gröger, M., Dutheil, C., Rhein, M., Borchert, L., and Radtke, H.: Atlantic Multidecadal Variability and the Implications for North European climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9125, https://doi.org/10.5194/egusphere-egu23-9125, 2023.

Since the seminal work of Walter Munk in the 1960s ('Abyssal Recipes'), oceanographers have believed that the upwelling of cold, abyssal waters that regulates the deep ocean's ability to sequester heat and carbon for decades to millennia is mainly driven by centimetre-scale turbulent mixing associated with breaking internal waves in the ocean interior. Measurements of deep-ocean turbulence over the last >20 years, however, have contested this scenario, and instead suggest that mixing by breaking internal waves drives *downwelling* of abyssal waters. Inspired by this conundrum, recent theoretical investigations have developed an alternative view of the role of mixing in sustaining deep-ocean upwelling. In this new view, upwelling is driven by highly localised turbulence within thin (typically tens of metres thick) layers near the seafloor, known collectively as the bottom boundary layer. In the BLT Recipes experiment, we recently set out to test this new view, and figure out how it works, by obtaining the first set of concurrent, systematic measurements of (1) large-scale mixing and upwelling, (2) their interior and bottom boundary layer contributions, and (3) the processes underpinning these contributions, in a representative deep-ocean basin (the Rockall Trough, in the Northeast Atlantic). This talk will review the insights emerging from the BLT Recipes experiment, and offer an outlook on how they might re-shape our understanding of the way in which turbulence sustains deep-ocean upwelling.

How to cite: Naveira-Garabato, A. C.: Rewriting the tale of deep-ocean upwelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16418, https://doi.org/10.5194/egusphere-egu23-16418, 2023.

Observations and model results provide two complementary sources of information on past climate variations. The paleo -or proxy - data characterize the changes that occurred at a particular time while models can be used to infer the mechanisms responsible for those changes. Observations and model results are thus ideally used jointly and the first step before applying models to study past and future climate is to evaluate their ability to reproduce the signal recorded in the data. Paleodata and model results can also be combined more profoundly using data assimilation. While classical model-data comparison can only assess the skills of the model, data assimilation can guide the model results to have a better agreement with the real observed changes and thus to reproduce more accurately the processes at their origin.

The main challenges in paleo data assimilation will be reviewed here. Issues related to the generation of the model results, the model data comparison and the data assimilation technique itself will be addressed. Some recent achievements and perspectives will then be presented, first for spatial reconstructions based on data assimilation and secondly for the quantification of internal and forced climate variability as well as the role of atmospheric and oceanic circulation in past climate changes.

How to cite: Goosse, H.: Combining model results and paleodata using data assimilation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1893, https://doi.org/10.5194/egusphere-egu23-1893, 2023.

Humans have impacted the hydrological cycle since the invention of agriculture, but these impacts have grown to global proportions over the last 60 years. The indirect effects of anthropogenic climate change may be the largest, but the direct impacts by dam building, water withdrawals and the emission of pollutants is still formidable, even by comparison. In the first part of this lecture, I will briefly go over the impacts of human water use on global hydrology and water resources and how these impacts have been assessed by observational evidence and global hydrological models. This will also provide the opportunity to highlight some recent advancements in global hydrological modelling. The second part of the lecture will focus on the impacts of human water use on groundwater resources. After reviewing past assessments of global groundwater depletion rates, I will show results of ongoing research in our group on the limits to global groundwater use. These include: physical limits, related to groundwater-surface water interaction, permeability constraints and salinity; economic limits, related to the costs of groundwater extraction when wells become deeper; and ecological limits, related to the impacts of groundwater extraction on groundwater dependent ecosystems.

How to cite: Bierkens, M.: Global Water Resources and the Limits to Groundwater Use, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1844, https://doi.org/10.5194/egusphere-egu23-1844, 2023.

Fossils in the mountains: Understanding the relationship between biodiversity and geography during the Early Palaeozoic

The eminent Alpine geologist, Rudolf Trümpy once stated, ‘One bad fossil is worth a good working hypothesis’. Although characterized by poor preservation, fossils have for many decades provided age and geographic constraints on the evolution of the World’s mountain belts. Palaeontological data helped expose horizontal and lateral crustal movements and signalled the importance of continental drift as a planetary-scale process. In Europe and North America the bioregionality of many fossil groups has provided key data for the definition of continents, microcontinents and volcanic arcs and their movements during the Early Palaeozoic. Moreover, identification of species pumps and refugia in the island terranes of the Iapetus and related oceans, now exposed along the length of the Caledonian-Appalachian orogenic belt, has enhanced our knowledge of the Great Ordovician Biodiversification Event and the Late Ordovician Mass Extinction. Mechanisms for the diversification and extinction of taxa can be hypothesized and many terranes hold key evidence on the early evolution and phylogeny of marine animal groups. The movement of most crustal units towards lower latitudes and their carbonate environments during the later Ordovician is correlated with the highest species richness of the period terminated by the intense, short-lived Hirnantian ice age.

How to cite: Harper, D.: Fossils in the mountains: Understanding the relationship between biodiversity and geography during the Early Palaeozoic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4207, https://doi.org/10.5194/egusphere-egu23-4207, 2023.

Paleoclimate archives, such as marine and terrestrial sediment cores, provide a valuable record of past climate conditions and can serve as "sentinels" for predicting future climate change. By using methods of sedimentology, stratigraphy, and paleontology, it is possible to reconstruct the physical and biological conditions of the past and gain a deeper understanding of how ecosystem stability has responded to changes in the environment. One excellent example of this is the UNESCO world heritage Messel fossil pit in central Europe, which dates back to the Eocene epoch and provides a glimpse into the potential future climate that may be experienced in 2150. Examining the annually laminated Messel sediments and building upon more than 60 years of paleontological excavations allows for insights into the sensitivity of terrestrial and aquatic ecosystems to environmental change under high greenhouse gas concentrations across orbital to interannual time scales. This can provide new and important constraints on aquatic ecosystem stability and potential teleconnections to the surrounding terrestrial realm in an ever-warming world. Understanding these complex interactions between terrestrial and aquatic ecosystems can inform decision-making and policy development related to climate change mitigation and adaptation.

How to cite: Kaboth-Bahr, S.: Paleoclimate archives as sentinels of future climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11406, https://doi.org/10.5194/egusphere-egu23-11406, 2023.

Until the 1970s, global hydrology had to rely on the collection of in-situ observational data and aggregation under condition when electronic computers were not sufficiently available. In the 1980s, earth observation data from artificial satellites began to observe clouds, precipitation, and later surface soil moisture content, and from the beginning of the 21st century, total terrestrial water storage, including groundwater and ice sheets. Along with this, data assimilation systems merging simulated forecasts by numerical models of the atmosphere and in-situ and satellite observations have been developed, and the information on global hydrologic cycles, at least regarding the atmosphere, has become available.

When we applied the atmospheric water balance method to the four-dimensional data assimilation (4DDA) data and compared it with the discharge of major rivers around the world, we found that the seasonal variation was captured well, although the quantitative accuracy was not sufficient. Seasonal variations in total terrestrial water storage are very large in the Amazon Basin and cannot be explained by changes in soil moisture alone. It was suggested that the changes in river water stored in the river channel contributed greatly, but it was necessary to wait until later GRACE observation data were available to obtain conclusive evidence.

In addition, when the atmospheric water balance method is applied, negative runoff is calculated in some regions and seasons, and at first it was thought to be an error in data and the data processing, and an ad hoc correction method was attempted. However, even from the composite of in-situ discharge data, some areas were found where the downstream river discharge was smaller than the upstream, and negative runoff should be estimated. Then, it became apparent that the negative runoff should be mainly due to anthropogenic water withdrawals and consumption, it is necessary to consider human activities in research targeting the actual water cycle, and such interventions can be detected even on a global scale.

Then, starting with storing in and releasing from reservoirs, an integrated water cycle and water resources model that considers human activities such as water withdrawals from rivers and groundwater, irrigation for farmlands, and long-distance water transport through canals has been developed and used. Although such a model was initially for a global scale, it can be applied for local simulation of hydrologic cycles in the Anthropocene considering water supply and sewerage systems and contribute to supporting scientific evidence-based decision makings.

Improvements in observational and computational capabilities alone did not support the development of global hydrology. In addition to the numerical model itself, it should be acknowledged to the development and sharing of critical global data such as topography, land use and land cover, and cropland distribution equipped for irrigation that are essential for proper simulation of the model. Global hydrology is a community-supported discipline and the gift of grassroots solidarity among researchers around the world.

How to cite: Oki, T.: Evolution of Global Hydrology in the Anthropocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4076, https://doi.org/10.5194/egusphere-egu23-4076, 2023.

In 2004, we painstakingly measured the thinning of a single glacier tongue (the Mer de Glace, Mont-Blanc) from pairs of SPOT (CNES) satellite optical stereo-images. It then took us nearly 20 years before we managed to up-scale such observations to the global scale. In this presentation, I will illustrate the advances (in terms of data availability and processing) and all the collaborative work that led to a spatially-resolved and almost complete estimation of mass changes for the more than 200,000 glaciers on Earth. These new data paint a global picture of accelerating glacier mass loss since 2000 and pave the way toward improved projections of future glacier mass and sea level contribution.

How to cite: Berthier, E., Belart, J., Blazquez, A., Brun, F., Deschamps-Berger, C., Dussaillant, I., Flament, T., and Hugonnet, R.: From the tongue of the Mer de Glace to the world’s glaciers : 20 years of progress in measuring glacier mass changes from space, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4976, https://doi.org/10.5194/egusphere-egu23-4976, 2023.

Glaciers outside the ice sheets are key contributors to sea-level rise and act as essential fresh-water resources in various regions around the world. Glaciers are also important sources of natural hazards, directly impact biodiversity, and have a significant touristic value. Given these crucial societal and environmental roles, having reliable projections on the evolution of these precious ice bodies under changing climatic conditions is of paramount importance.

In this presentation, I will highlight how modelling glacier changes goes hand in hand with rapidly increasing remotely sensed glacier observations and derived products at the global scale (e.g., glacier outlines, surface elevation, ice thickness, surface velocities, and elevation changes). These new observations, combined with ever-increasing computational capacities and novel numerical tools have recently allowed us to transition from modelling a few individual glaciers to now modelling the evolution of glaciers at regional- to global scales while accounting for ice-dynamical processes. Whereas these recent advances are encouraging, I will also highlight the challenges that we are still facing and that we will need to tackle in the coming years to provide more trustworthy glacier evolution projections.

How to cite: Zekollari, H.: Changing glaciers in a changing climate through changing modelling approaches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9607, https://doi.org/10.5194/egusphere-egu23-9607, 2023.

Early studies of “geo-magnetism” dealt with the understanding of long-term developments and short-term disturbances in the geo-magnetic field as measured by magnetometers on ground level. Soon after the IGY the concept of several co-existing and globally or locally interacting ionospheric current systems (DP1 & 2) was born. Both systems seemed to respond differently to solar wind driving conditions and internal magnetospheric processes. Through continued global international study efforts, like e.g. the International Magnetospheric Study (IMS) and later the International Solar Terrestrial Physics program (ISTP) the 2-dimenional monitoring of geomagnetic “disturbances”, now understood as complex signatures of different current systems within and beyond the upper atmosphere, became a powerful tool to monitor and study the complicated three-dimensional coupling of the magnetosphere to the upper atmosphere and its ultimate relation to certain solar wind drivers of magnetospheric conditions.

Geomagnetic observations, both globally and regionally, are today a valuable asset to put the very local measurements of magnetospheric satellites (even if “multi-point”) into its proper context with respect to the dynamics of the magnetosphere. The ultimate goal of such measurements today is not only to identify the energy and activity state of the magnetosphere as such, but also to study the exact location, strength and spatio-temporal development of the most powerful short-lived magnetic disturbances that we know, the so-called magnetospheric substorms and the closely related intensifications of major magnetic storms.

The study of the physics of the geo-space environment in response to solar activity and solar wind driving has over the last twenty years matured to make first useful predictions of a large variety of plasma processes in near-Earth space, which have the potential to detrimentally affect human space exploration and human technological infrastructure both on ground and in space. The fast-growing research and operational field of Space Weather has stimulated new active research (including advanced model efforts) to get to the bottom of some of the most effective geo-space plasma phenomena, and to understand the variability of ionospheric currents, and their connection to the outer magnetosphere. This is at present one of the most intriguing scientific problems in the field of Space Weather. Potentially any conducting infrastructure on the ground can be detrimentally or catastrophically affected by fast changes in the magnetic field (dB/dt) via geomagnetically induced currents (GICs). In parallel, the involved ionospheric current systems can cause further secondary impacts on space-borne communication and navigations systems via ionospheric plasma instabilities and atmospheric drag effects on satellite orbits.

In my presentation I will give a short background to the historical progress of space science with the help of magnetometer data, and then highlight a selection of recent research topics, where global and regional magnetometer networks (together with a multitude of dedicated space missions) represent a very important part of the systematic and coordinated study of the near-Earth plasma environment, the coupled solar wind - magnetosphere - ionosphere – atmosphere “System of Systems”.

How to cite: Opgenoorth, H.: From Geomagnetism and Space Science to Space Weather, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8054, https://doi.org/10.5194/egusphere-egu23-8054, 2023.

The talk is devoted to a discussion of different  typologies of models:

 I-  Oversimplified models;

 II- Models by analogy;

  III- Large scale models;

IV- Models from data. 

In the class  I  there is the celebrated   Lorenz model; the  Lotka-Volterra  system  is in the class  II, and it is at the origin of biomathematics.

Among the  models in the class III  we have the effective equations used, e.g., in meteorology and engineering,  where only "relevant variables" are taken into account.

In the class  IV we find the most interesting (and difficult) problem:the building  of models just from datawithout a reference theoretical framework.

How to cite: Vulpiani, A.: The Role of Theory and  Data in Model Building:  from Richardson to   machine learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2654, https://doi.org/10.5194/egusphere-egu23-2654, 2023.

The Arctic is warming at a rate greater than the global average. End-of-summer minimum sea ice extent is declining and reaching new minimums for the historical record of the last 4 decades. The Greenland ice sheet is now losing more mass than it is gaining, with increased surface melting. Earth System Models suggest that these trends will continue in the future. The geologic past can be used to inform what could happen in the future. Emiliani in his 1972 Science paper commented on the relevance of paleoclimate for understanding our future Earth.

Interglacials of the last 800,000 years, including the present (Holocene) period, were warm with low land ice extent. In contrast to the current observed global warming trend, which is attributed primarily to anthropogenic increases in atmospheric greenhouse gases, regional warming during these interglacials was driven by changes in Earth’s orbital configuration. Although the circumstances are different, understanding the behavior, processes, and feedbacks in the Arctic provides insights relevant to what we might expect during future global warming.

Data compilations suggest that despite spatial heterogeneity, Marine Isotope Stages (MIS) 5e (Last Interglacial, ~129 to 116 ka) was globally strong. The Last Interglacial (LIG) is characterized by large positive solar insolation anomalies in the Arctic during boreal summer associated with the large eccentricity of the orbit and perihelion occurring close to the boreal summer solstice. The atmospheric carbon dioxide concentration was similar to the preindustrial period.

Geological proxy data for the LIG indicates that Arctic latitudes were warmer than present, boreal forests extended to the Arctic Ocean in vast regions, summer sea ice in the Arctic was much reduced, and Greenland ice sheet retreat contributed to the higher global mean sea level. Model simulations provide critical complements to this data as the they can quantify the sensitivity of the climate system to the forcings, and the processes and interplay of the different parts of the Arctic system on defining these responses. As John Kutzbach explained in a briefing for science writers, "climate forecasts suffer from lack of accountability. Their moment of truth is decades in the future. But when those same computer programs are used to hindcast the past, scientists know what the correct answer to the test should be."

Significant attention and progress have been made in modeling the LIG in the last 2 decades. Earth System Models now capture more realism of processes in the atmosphere, ocean, and sea ice, can couple to models of the Greenland ice sheet, and include representations of the response of Arctic vegetation to the NH high-latitude summer warming. Increases in computing power has allowed these models to be run at higher spatial resolution and to perform transient simulations to examine the evolving orbital forcing during the LIG.  The international PMIP4 simulations for 127 ka illustrated the importance of positive cryosphere and ocean feedbacks for a warmer Arctic. A CESM2-Greenland ice sheet, transient LIG simulation from 127 ka to 119 ka, established a key role of vegetation feedbacks on Arctic climate change.

How to cite: Otto-Bliesner, B. L.: Milankovitch cycles and the Arctic: insights from past interglacials, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9748, https://doi.org/10.5194/egusphere-egu23-9748, 2023.

Petrus Perigrinus de Maricourt, a French physicist and mathematician wrote the first descriptions of the properties of magnets, now known as the Epistola de Magnete in 1269.  He summarized what was known at the time concerning the use of the compass, writing “that while the investigator in this subject must understand nature and not be ignorant of the celestial motions, he must also be very diligent in the use of his own hands, so that through the operation of this stone he may show wonderful effects.” (translation by J. Gimpel, 1976).  This is still true today, particularly for those of us who study the ancient magnetic field through ‘accidental’ records in geological and archaeological materials.  In this lecture I will review efforts to use ‘our own hands’ to understand the structure of the time averaged Earth’s magnetic field over the last five million years, using both directions (obtained with compasses!) and intensities.

How to cite: Tauxe, L.: Hunting the Magnetic Field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1788, https://doi.org/10.5194/egusphere-egu23-1788, 2023.

Permeability is a key physical property across all spatial scales in the Earth’s crust and exerts significant control on the behaviour of Earth systems, with implications for natural hazards (e.g., earthquakes, slope instabilities, volcanic eruptions) and geo-resource management (e.g., geothermal energy, carbon capture and sequestration, ore deposit formation). Amongst other processes, rock-fluid interactions and the interplay between precipitation and dissolution complicates the microstructure of these materials, modifying the efficiency of fluid flow. For example, the permeability of volcanic rocks is generally controlled by the presence of pores and microfractures, but the continuum from pore-dominated to microfracture-dominated permeability is significantly perturbed by the introduction of alteration minerals that reduce the void space available to fluid flow over time. The propensity, extent, and timescales of rock alteration are therefore important factors influencing rock permeability. However, obtaining a systematic understanding of the intricate relationships between rock alteration and changes in permeability – including dissolution, transport, and redistribution of chemical compounds – is challenging. As a result, we do not fully understand how these processes modify the structure of permeable channels and over what timescales they may hamper fluid flow, limiting our ability to effectively model, for example, geothermal reservoirs or volcanic processes.

The mission of the new Rock Physics and Geofluids (RPGL) group at EPFL is to address how secondary mineral precipitation – starting with silica (SiO₂) - changes the permeability of rocks. Using a mix of rock physics, microstructural and geochemical characterization, and water-rock interaction experiments, we will quantify 1) the physical and chemical conditions promoting silica alteration under a wide range of crustal conditions, 2) how the geometry of fluid-flow pathways in rocks changes over time, 3) how these changes modify permeable flow, and 4) on what timescales these processes are active. Our goal is to establish the infrastructural, experimental, and analytical foundation needed to more broadly study the relationships between rock-fluid interactions and fluid flow, for potential application to natural hazard and geo-energy research.

How to cite: Kushnir, A.: Permeability, alteration, and microstructure: A (hopefully) coupled rock physics and geochemical approach to how rock-fluid interactions change permeability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4505, https://doi.org/10.5194/egusphere-egu23-4505, 2023.

Growth and death of microorganisms is central to the understanding of almost all global element cycles. To grow, heterotrophic microorganisms need to assimilate organic carbon, and to sustain a flux of readily available organic carbon, they need to depolymerize and deconstruct soil organic matter. When soil organisms die, their remnants become part of the soil organic matter. Thus, the processes that lead to both the decomposition and the accumulation of organic matter in terrestrial environments, are driven by the growth, activity and turnover of heterotrophic microbial communities in soil. Yet, little is known about how microbial growth, turnover, and activity is controlled in the current and in a future climate. In this lecture, I will share insights from a range of experiments that aimed at understanding the effects of soil warming, elevated CO_2, and drought, alone or in combination on microbial growth, turnover, and carbon use efficiency. I will draw on examples not only from my own work, but those of others, covering different levels of resolution, from the growth of microbial communities to that of individual bacterial taxa. I will argue that activity, growth, and turnover of microorganisms are the fundamental units of biogeochemical functioning in soils and that we need to move beyond the commonly reported metrices in soil ecology, and even beyond measuring rates of decomposition and mineralization themselves, if we are to understand the effects of climate changes on soil processes.

How to cite: Richter, A.: What controls carbon and nutrient cycling in soil? Microbial growth as the fundamental driver of soil biogeochemistry., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10907, https://doi.org/10.5194/egusphere-egu23-10907, 2023.

Black Swans in river flood hydrology are unexpected events that surprise flood managers and citizens, causing massive impacts when they do occur, but that appear to be more predictable in retrospect, after their occurrence. My talk aims at showing how black swans in river flood hydrology can "be made grey", i.e. can be anticipated to a certain degree, in probabilistic terms, and/or made less impactful, by (1) expanding information on flood probabilities by gathering data on floods occurred in other places and at other times; (2) understanding the mechanisms causing heavy tails in flood frequency distributions; (3) understanding the mechanisms causing river flood changes in time; (4) accounting for uncertainties in data, models and flood frequency estimates; (5) accounting for the possible dynamics of coupled human-water systems; and (6) coupling the classical top-down approach to hydrological risk assessment based on predictive modelling with a bottom-up approach that is centered on robustness and resilience.

How to cite: Viglione, A.: Extremes in river flood hydrology: making Black Swans grey, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2227, https://doi.org/10.5194/egusphere-egu23-2227, 2023.

Since the end of the 19th century, geomorphologists have been on a relentless quest to unravel the mysteries of landscape evolution and explain the diversity of the resulting forms. However, a quantitative model of landscape morphodynamics that is relatively universal and applicable at various time scales still eludes us. This raises an important question: are we, geomorphologists, dumber than the average scientist, or is landscape evolution particularly complex to decipher? ChatGPT tells us that, indeed, landscape evolution is complex. 

As for many natural phenomena, the complexity of landscape evolution results from 3 elementary components: processes, stochasticity, and heterogeneity. Process geomorphology tackles the complex morphodynamics emerging from the diversity and interactions of physical, chemical, and biological processes that shape the Earth. Stochastic geomorphology addresses the role of fluctuations in the drivers of landscape evolution, such as the frequency-magnitude distribution of precipitation events, landslides, earthquakes, or fires. Heterogeneous geomorphology embraces the variable nature of the properties of landscape elements on which geomorphic processes operate or that they create. This includes, for instance, the distribution of grain sizes, the diversity of rock type, the fractal nature of rock fractures, or the spatial variations in vegetation size and type.

Accounting for all these sources of complexity, inasmuch as they can be quantified, is an untractable problem resulting in models of little explainability. Therefore, hypotheses had been and must be formulated to simplify the problem of landscape evolution comprehension and modeling. There is, arguably, a long tradition of emphasizing process complexity to explain landscape dynamics, neglecting or simplifying both stochastic fluctuations and heterogeneity. In this lecture, I shall discuss this view, emphasizing the now well-established importance of stochastic fluctuations, and how little we know of the role of heterogeneity.

On this latter topic, I shall illustrate with a variety of examples how time series of high-resolution and high-precision topographic data (4D data) offers unprecedented insights into landscape morphodynamics. Beyond quantifying and detecting a variety of processes and their temporal fluctuations, 4D data allow a systematic quantification of the heterogeneity (e.g., vegetation, grain size, ...) of landscape elements, and spatial variability of geomorphic rates, thus bringing us closer to formulating the role of heterogeneity in landscape dynamics. Yet, this goal can only be achieved if tools to harness the complexity and richness of high-resolution topographic data are developed and made available.

Keywords: fluvial incision, landslides, floods, salt marshes, topo-(bathymetric) LiDAR, numerical modeling, machine learning.

How to cite: Lague, D.: Coping with the complexity of landscape evolution and how high-resolution topography can help, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10371, https://doi.org/10.5194/egusphere-egu23-10371, 2023.

For more than 30,000 years, humans have been able to characterise materials, so they could choose the best for making tools, jewellery, shelter and clothing. For more than 300 years, scientists and craftsmen have known enough about fluids to characterise them and use them, even if they never succeeded in precipitating gold from solutions of lead. However, it has only been the last 30 years that we have been able to characterise the composition and structure of the mineral-fluid interface with techniques that can "see" at the nanometre scale and to simulate interactions from first principals. Once one can understand the mechanisms that control the solid-fluid interface, one can control the material’s properties and its behaviour. This is the key to designer materials and solving challenges in nature.

My journey into the nanometre scale world of interfaces began with demonstrating that the surface of a calcite crystal is not simply a termination of the bulk structure. Instead, it is a defect, where the atoms at the interface are restructured. In response to fracture in a vacuum or in contact with gas, water or organic compounds, the atoms of the mineral surface rearrange and the molecules in the fluid in contact organise themselves to delocalise charge differences between each other and with the surface. This plays a role in the behaviour of adsorbates. In turn, ion and organic compound adsorbates can modify surface properties, dramatically changing behaviour, even at tiny fractions of a monolayer. Understanding mineral-fluid-organic compound interactions gives us a powerful tool, the ability to predict behaviour and to control reactions.

Work in my group shows that the character of simple organic compounds, i.e. their functional group(s), size and branching, determine their adsorption energy on calcite. Density functional theory simulations match very well with adsorption energy determined with X-ray photoelectron spectroscopy. If we can define such relationships for other mineral systems, it could lead to a whole new conceptual framework for describing and predicting mineral-water-organic compound reactivity.

How to cite: Stipp, S.: Mineral-fluid reactivity: The action is at the interface, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17120, https://doi.org/10.5194/egusphere-egu23-17120, 2023.

How to cite: Lichtenberg, T.: Tectonics and magma oceanography of rocky exoplanets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1707, https://doi.org/10.5194/egusphere-egu23-1707, 2023.

A planet which is warm enough so that it lies above the gas/liquid critical point and above the solidification line of its main constituent is a fluid planet. This is the case of Jupiter and Saturn, and of all planets in the Universe that are dominated by hydrogen, due to its very cold critical point (33K) and low melting temperature. Planets mainly made of other elements than hydrogen and helium, such as water, may also be fluid, if they are close enough to their star. Hydrogen, helium and oxygen being the most abundant elements in the Universe, fluid planets hold some of the keys to understand our origins.

Being fluid implies that these planets have low viscosities and few barriers to convection and mixing. They are governed by the same hydrostatic equations as stars. The progressive transition between the gaseous atmosphere and the fluid interior allows one, in principle, to infer bulk composition from the atmospheric one. Behind their apparent simplicity, complications arise rapidly: How do these planets rotate? How efficiently would they mix other elements, particularly in the presence of condensation and clouds, but also when this is energetically unfavored? What is the effect of intense irradiation on the global heat transfer? 

Over the past 30 years, solutions or partial solutions to these questions have been provided thanks to a combination of theoretical studies and observations. Simple theories of the evolution and atmospheric properties of exoplanets have proven relatively successful. Advances in gravitational sounding of Jupiter and Saturn have provided the basis to understand and predict how fluid planets rotate. Constraints on the structure of the planets and on the presence of primordial dilute cores have been provided.  

Yet, recently, thanks to the Juno and Cassini observations, evidence of imperfect mixing and stable regions have arisen both in the deep atmosphere and interior of Jupiter and Saturn. Observed latitudinal and temporal variability in composition, lightning or general atmospheric properties have remained unaccounted for. Modeling atmospheric properties of fluid planets based on Earth parameterizations, not fully accounting for their abyssal nature and moist convection inhibition has failed. Fluid planets are more complex and challenging than previously envisioned. 

Progress will come from the continuation of a combination of studies: theoretical and numerical studies to understand heat transfer and mixing in the presence of condensation, observations of a large variety of exoplanets and measurements in solar system fluid planets. But the next milestone lies in the outer solar system, with the exploration of Uranus and Neptune. These planets are only partially fluid and may have a solid interior. This increased complexity matches what is to be expected for other planets in the Universe. Their atmospheres, made of hydrogen and helium and large amounts of methane, are laboratories to test models of heat and element transport in abyssal hydrogen atmospheres. An international mission with an orbiter and a probe would allow for the direct measurements that we need in order to interpret with confidence the great wealth of data awaiting us with the more distant exoplanets. 

How to cite: Guillot, T.: Fluid Planets: from Theory to Observations and Beyond, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8554, https://doi.org/10.5194/egusphere-egu23-8554, 2023.

Mountain torrents and debris flows are widely distributed in the mountainous region, threatening the urban development and infrastructure in mountain areas. The adverse effects of these hazards may increase due to the continued socio-economic development and influence of climate change on the frequency and magnitude of the hazards. This lecture introduces an early warning system of mountain hazards based on hazards process simulation and associated risk forecasting. The system identifies the watershed with high susceptibility to mountain hazard occurrences by monitoring the hazard-fostering conditions and real-time meteorological data. Focusing on those watersheds, the formation and movement of the hazards were simulated while different characteristics were captured, such as debris flow scale amplification and flash flood erosion. The risk of the mountain hazards was assessed based on the whole process of disaster formation-movement-deposition/disaster-causing. Compared with traditional early warning systems, which largely rely on rainfall thresholds and expert judgment, this proposed system is fully data-driven and process-based, while little human intervention is required. This system provides more accurate early warning information, and risk forecasting can better support disaster response planning for the government agency. This system is currently under trial in Liangshan Prefecture, Sichuan Province of China. Just in 2022, 15 debris flow and 52 flash flood events were captured and the early warning information was delivered to the residents and government. The accuracy is more than 79% and significantly improved the disaster resilience of the mountainous region.

About the Presenter

 Prof. CUI Peng has long been engaged in research on the formation mechanism, risk assessment, monitoring and early warning, prevention and control technology of debris flows and other mountain hazards. He has given a strong pulse to several topics of major relevance for disaster risk reduction and management, including (1) deepening the understanding of debris flow formation, scale amplification, and disaster-causing mechanisms; (2) providing rigorous insights concerning the formation and evolution of earthquake-induced hazards and multi-hazard chaining effect; (3) development of multi-scale disaster risk assessment model; (4) building of risk-level-based monitoring and early system to support efficient disaster reduction; and (5) creating the mass control and energy-based disaster mitigation theory and technology. He has published more than 400 papers with over 12000 citations and is the world's most published scholar in the field of debris flow.

How to cite: Cui, P.: A data-driven and process-based system for mountain torrent and debris flow early warning and risk forecasting, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17044, https://doi.org/10.5194/egusphere-egu23-17044, 2023.

Hotspots, sites of mid-plate or excessive volcanism, overlie plumes of hot rock that rise in the solid state from Earth’s deep mantle. Estimated rates of lateral hotspot motion since Late Cretaceous time have been as low as ≈3 mm/yr to as high as ≈80 mm/yr. We focus on geologically current (i.e., neotectonic) motions because the precision and accuracy of relative plate motions in the MORVEL set of relative plate angular velocities (DeMets et al., 2010) are an order of magnitude greater than plate motion estimated for earlier time intervals.  Prior efforts to estimate neotectonic relative motion between hotspots from trends of hotspot tracks found no significant difference from zero motion (i.e., they are consistent with fixed hotspots) and no useful upper bound on the rate of motion (e.g., Minster et al., 1974; Gripp & Gordon, 1990, 2002).

Our recent analysis builds on methods to objectively estimate the uncertainty of hotspot trends. We use the uncertainties estimated by Gripp & Gordon (2002) and by Wang et al. (2019a) for the hotspot trend data set of Morgan & Morgan (2007).  The objectively estimated uncertainties tend to be larger than those assigned by Morgan & Morgan (2007), especially for slow moving plates.  In a global inversion of the observed trends, a chi‐square test indicates that the trends and adopted uncertainties are consistent with fixed hotspots (p=0.08; p < 0.05 would indicate significance). When we conduct a two‐tier analysis, however, the motion between groups of hot spots is significant. The group‐means of trend‐perpendicular component of velocity range in nominal magnitude from 0 to 6 mm/a with a median of ≈3 mm/a.  Wang et al. (2019b) applied these data and uncertainties to investigate how well the hotspot motion predicted by Doubrovine et al (2012) in their Global Moving Hotspot Reference (GMHRF) fit the observations.  Surprisingly the GMHRF fits the observed trends much worse than they are fit assuming fixed hotspots.

The key to our newest analysis, which attains far higher resolution than before, is the novel use of Monte Carlo inversion to find directions and rates of hotspot motion that misfit the observed trends by angles consistent with the uncertainties in the trends. We obtained one million pseudorandom realizations of the direction of motion of each of 53 hotspots and inverted for the rate of hotspot motion that best fits the observed hotspot trend data.  We examined speeds ranging from 0 to 15 mm/yr in increments of 1 mm/yr.  For 60% of the realizations the best-fitting hotspot speed is 0 mm/yr, i.e., no motion between hotspots. Forty per cent of the realizations are fit better with some motion between hotspots with merely 2% of the realizations being fit acceptably close to the misfit expected given the size of the uncertainties.  No realizations gave an acceptable fit with motion less than 2 mm/yr or with motion exceeding 8 mm/yr; the 95% confidence interval is 2–4 mm/yr, significantly different from zero, but low enough to strongly support the use of the fixed hotspot approximation.

How to cite: Gordon, R., Gaastra, K., Mifflin, G., and Wang, C.: Neotectonic Rates of Motion Between Hotspots, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4551, https://doi.org/10.5194/egusphere-egu23-4551, 2023.

Current developments in quantum physics and the application of general relativity open up advanced prospects for satellite geodesy, gravimetric Earth observation and reference systems and thus strongly help to meeting the geodesy challenges in a unique way. As Vening-Meinsz advanced gravimetry 100 years ago with his pendulum apparatus, quantum optics can push it further using atoms today. These novel concepts include the application of atom interferometry for realizing quantum gravimetry and gradiometry, the enhanced use of laser interferometry for inter-satellite tracking and accelerometry at future gravity field missions, and relativistic geodesy with clocks for the determination of gravity potential differences via gravitational redshift measurements.

We briefly illustrate those novel techniques and present in which fields geodesy and geosciences will benefit from them. We show various application areas ranging from the direct determination of physical heights and the monitoring of mass variations using clock networks up to the use of quantum technology for gravimetric Earth observation on ground and in space. Realizing these innovative methods is key to quantify climate change processes (groundwater changes, ice mass loss, seal level rise, etc.) with largely increased precision and resolution.

Finally, we would like to mention the IAG project “Novel Sensors and Quantum Technology for Geodesy (QuGe)” that advances those activities in close collaboration between geodesy and physics, see https://quge.iag-aig.org/  -  see also: Van Camp, M., Pereira dos Santos, F., Murböck, M., Petit, G., Müller, J. (2021): Lasers and Ultracold Atoms for a Changing Earth. EOS, 102, https://doi.org/10.1029/2021EO210673

Acknowledgment: This study has been funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy EXC 2123 Quantum Frontiers - Project-ID 90837967 and the SFB 1464 TerraQ - Project-ID 434617780.

How to cite: Müller, J.: Benefit of Quantum Technology for Geodesy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5719, https://doi.org/10.5194/egusphere-egu23-5719, 2023.

Glacial isostatic adjustment (GIA) describes the response of the solid earth to ice mass changes and corresponding changes in the sea level. This process is visible in various geoscientific observations, with geodetic measurements being crucial to understand and describe the process. For example, the vertical and horizontal motion of the lithosphere is visible in GNSS (Global Navigation Satellite Systems) time series in the currently (Greenland, Antarctica, Svalbard) and formerly glaciated regions (North America, northern Europe). In addition to geodetic observations of GIA, the solid earth deformation is visible in various geological data. The vertical motion of the lithosphere can be seen in relative sea level and lake level data, but for a different epoch then GNSS data. All these observations help to explain GIA as well as infer the structure of the Earth via so-called GIA models. GIA models can be constrained by geodetic and geological observations and in turn can help to predict these observations. An essential component of GIA models is knowledge about the distribution of material parameters of the Earth’s lithosphere and mantle. This can be obtained from various geophysical measurements (e.g., gravity, seismology).

Here, I will show how we can infer the depth of various material layers in the lithosphere from geodetic data exemplary for Greenland and how we can use these in three-dimensional GIA models. I will also discuss the effect of various lithosphere models on the modelled GNSS velocities.

How to cite: Steffen, R.: Geodesy meets tectonophysics: Advancing our estimates of glacial isostatic adjustment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11261, https://doi.org/10.5194/egusphere-egu23-11261, 2023.

Acidity is one central parameter in atmospheric multiphase reactions, and strongly influences the climate, ecological and health effects of aerosols. Yet, the drivers of aerosol pH remain to be fully resolved. Here we investigated into this issue with thermodynamic models and observations. We find that aerosol pH levels in populated continental regions are widely buffered by the conjugate acid-base pair NH₄⁺/NH₃, and in aerosols an individual buffering agent can adopt different buffer pH values. To explain these large shifts of buffer pH, we propose a multiphase buffer theory, and show that aerosol water content and mass concentration play a more important role in determining aerosol pH in ammonia-buffered regions than variations in particle chemical composition. These results imply that aerosol pH and atmospheric multiphase chemistry are strongly affected by the pervasive human influence on ammonia emissions and the nitrogen cycle in the Anthropocene. We further investigated into the applications of the multiphase buffer theory. Exemplary applications include to help explain the formation of severe hazes in China, to quantify the contribution of different factors in driving the aerosol pH variations, and to provide the framework to reconstruct long-term trends and spatial variations of aerosol pH, etc. Further investigations on its applications in aerosol and cloud chemistry studies are needed.

How to cite: Zheng, G.: Multiphase buffer theory: explanations of contrasts in atmospheric aerosol acidity and its applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4082, https://doi.org/10.5194/egusphere-egu23-4082, 2023.

Currently major efforts are underway toward refining the horizontal grid spacing of climate models to about 1 km, using both global and regional models. Such resolutions have been used for about a decade in limited-area numerical weather prediction applications and have demonstrated significant improvements in the representation of convective precipitation events (thunderstorms and rain showers). There is the well-founded hope that these benefits carry over to climate models, as the approach enables replacing the parameterizations of moist convection and gravity-wave drag by explicit treatments.

In this presentation, we will review three areas of km-resolution climate modeling. First, consideration will be given to an ensemble of km-resolution simulations from the CORDEX-FPS program on convection-permitting climate modelling, with a computational domain covering the greater Alpine region. This addresses the occurrence of short-term heavy precipitation events including their impacts such as flash floods, hail, and lightning. Results demonstrate the benefits of high computational resolution, in particular for the representation of short-term heavy events of severe weather. Second, we will present recent results from the projects trCLIM / CONSTRAIN carried out over the tropical and subtropical Atlantic, with the goal to assess the potential of the methodology to constrain estimates of the equilibrium climate sensitivity. It will be argued that km-resolution is a highly promising approach for constraining uncertainties in global climate change projections, due to improvements in the representation of tropical and subtropical clouds that goes along with an improved representation of the intertropical convergence zone (ITCZ).

Third, technical aspects of developing km-resolution global models will be addressed. Developing this approach requires a concerted effort between climate and computer sciences. Key challenges are the exploitation of the next generation hardware architectures using accelerators (e.g. graphics processing units, GPUs), the development of suitable approaches to overcome the output avalanche, and the consistent maintenance of the rapidly-developing model source codes on a number of different compute architectures. Despite these challenges, it will be argued that km-resolution GCMs with a capacity to run at 1 SYPD (simulated year per day), might be much closer than commonly believed. However, as the computational load of CMIP-style simulations is tremendous, alternative ways to exploit these models will be needed.

How to cite: Schär, C.: Kilometer-resolution climate models: prospects and challenges, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9284, https://doi.org/10.5194/egusphere-egu23-9284, 2023.

River ecosystems are superlatives in many respects. Their networks represent the largest biogeochemical nexus between the continents, oceans and atmosphere. River networks span multiple catchments, even biomes, and are highly dynamic in space and time. The world’s rivers contribute relatively little by areal extent, but their CO₂ emissions are of the same magnitude as the CO₂ sequestration flux by the world’s oceans. Rivers figure among the most heterotrophic ecosystems on Earth, metabolizing terrestrial organic carbon. Owing to their dendritic structure, the biodiversity that river networks host is exceptionally high. Finally, needless to emphasize how critical the ecosystem services are that rivers provide. Central to many of these river superlatives are microbial biofilms that abundantly coat the sedimentary surfaces of the river beds. A microbiome, encompassing all three domains of life, shapes, in conjunction with the turbulent nature of water flow, intriguing biofilm architectures. Biofilms, a hidden beauty emanating from the interactions between biology, physics and chemistry, regulate ecosystem energetics and are therefore an important linchpin between river biodiversity and biogeochemistry.

In my lecture, I will attempt to provide the state-of-the-art of global river carbon biogeochemistry and biofilm ecology. An emphasis will be given on the rivers that literally drain the roof of our planet, now at risk because of climate change. It is my hope, that soon we will appreciate the world’s river networks as we do appreciate the oceans and various terrestrial ecosystems.

How to cite: Battin, T. J.: River ecosystems: A tale of superlatives and hidden beauty, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8898, https://doi.org/10.5194/egusphere-egu23-8898, 2023.

Study of past carbon cycle perturbation events is fundamental for assessing Earth’s climatic and ecological sensitivities, and our planet’s overall biogeochemical functioning and responses. Major hindrance to our understanding is the lack of reliable CO₂ estimates from Earth’s ‘deeper’ geologic past. I will summarize my work on CO₂ reconstruction from the rock record and make the case that boron isotope values of brachiopod shells serve as a robust CO₂ proxy. I will first present evidence from culturing experiments and natural marine settings demonstrating that the boron isotope composition of recent brachiopod shells responds predictably to the coupled ocean pH and CO₂ system, and provide a calibration that enables its accurate quantification. Next, I will showcase ocean pH and CO₂ records for some of most crucial yet enigmatic events in Earth’s evolutionary history, including the Permian-Triassic mass extinction, and discuss the causes and consequences of CO₂ change and its biogeochemical impacts during extinctions and events of abrupt environmental change. Finally, I will highlight recent progress and new capabilities to lay out a roadmap towards robust record of Phanerozoic CO₂.

How to cite: Jurikova, H.: Causes and consequences of environmental perturbations through the Phanerozoic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9859, https://doi.org/10.5194/egusphere-egu23-9859, 2023.

The transition towards carbon-free, renewable based energy systems is a central element to limit global warming and is one of the key societal challenges we are currently facing. The subsurface offers many different pieces for the energy transition jigsaw, from renewable energy from geothermal sources to large volumes of pore-space to permanently sequester carbon dioxide. The subsurface also provides several options for storing renewable energy over seasonal timescales, by storing renewable energy surplus converted into hydrogen and compressed air. As the subsurface can be utilized for many different energy related purposes, it becomes clear that it has to be a crucial part of the energy-transition.  However, most subsurface utilization technologies are not yet used on the scale that is needed for a successful energy transition. One reason for this lies in the incomplete understanding of (geological) processes that occur in the subsurface during, and after, the operation of these technologies. Predicting the performance and the potential of subsurface utilisation in the energy transition can also be hampered by limited data availability and the uncertainties associated with sparse datasets. Here, some of the key geoscience challenges that need to be solved for a timely energy transition are presented and some potential solutions are reviewed. The subsurface can, and must, play an important role in tomorrow’s green energy systems!

How to cite: Miocic, J.: The role of the subsurface in the energy transition – (some of) the (scientific) challenges, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11361, https://doi.org/10.5194/egusphere-egu23-11361, 2023.

Metamorphic rocks are composed of minerals formed within a wide range of pressure-temperature (P-T) conditions. These minerals possess distinct physical properties with respect to their thermo-elasticity, viscosity and plasticity etc. When far-field nonhydrostatic stress was present during tectonic deformation or the P-T conditions were changed during burial or exhumation processes, grain-scale stress variation can be developed to maintain mechanical equilibrium. The induced stress variations can also be released over geological time. The magnitude, effect and geological implications of the preserved stress variations have been investigated and better understood in recent years, but a lot remains to be explored. It is important because it may as well open an opportunity to decipher the overseen information stored in the rock that is difficult to be detected or achieved with conventional methods.

The geological implication of grain-scale stress variation is directly manifested by a simple mineral inclusion-host system, such as quartz or zircon inclusion in garnet. The different thermal-elastic response between the inclusion and host upon P-T changes will result in a residual stress stored in an entrapped mineral inclusion. The inclusion stress (strain) can be directly measured with e.g. Raman spectroscopy. Combined with an elastic model, it is possible to obtain constraints on the entrapment P-T conditions. This elastic thermobarometry technique has been applied in many recent petrological studies because no global or local chemical equilibrium assumption is needed. However, it relies on the inclusion-host system being elastic and neglects the non-elastic behavior of minerals. As an example, I will present an integrated observational, experimental and numerical modelling work that highlights the importance of considering non-elastic behaviour of the mineral. The heating experiment shows that under conditions at which free fluid is present, a garnet host will be drastically weakened and partially release the inclusion pressure. This is further correlated with a nappe-scale study in the Adula nappe, Alps. A smooth T gradient is found increasing from the north (500-550 ^oC) to the south (700 ^oC) using the Zr-in-rutile thermometer. However, the entrapment P calculated with the quartz inclusion in garnet barometer demonstrate a GPa level steep drop in the middle-south, where the rocks have been hydrated during retrograde metamorphism and abundant micro-hydrous inclusions (e.g. chlorite, amphibole) are found in the garnet. It is interpreted that a combined effect of temperature and water fugacity will drastically speed up the inclusion pressure relaxation on a regional metamorphic scale. In the end, it is highlighted that mechanics with non-elastic stress-strain (rate) relationships are potentially needed when dealing with the generation and dissipation of the stress variations in metamorphic rocks that underwent retrograde hydration or very high T conditions to better extract geological information.

How to cite: Zhong, X.: The generation, dissipation and geological implication of grain-scale stress variation in metamorphic rock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9133, https://doi.org/10.5194/egusphere-egu23-9133, 2023.

The wide use of the NDT technologies and the big database are produced, transmitted, collected, processed needs to be managed and well-presented towards monitoring of road transports. Using Ground Penetrating Radar (GPR) as one of the most efficient non-destructive tests in road transport monitoring.  Such database outcomes produced through on-site monitoring approaches are essential for providing the most reasonable decision-making tools to support best engineering judgment on-site. In addition to that the accuracy and precision of such decision-making tools are highly dependent on the data quality generated from different GPR images. Establishing performance indictor could avoid errors in dataset and unfavorable decisions in pavement management system. Consequently, GPR data management and transforming to local indicators is crucial to increase quality control of the dataset. This is still an ongoing challenging task for GPR support-knowledge.  

Establishing indicators are based on different criteria including intuitive outcomes, empirical outputs, and analytical results. Different GPR signal parameters can be correlated to the subsurface material changes and deterioration such as electromagnetic wave velocity, amplitude, centre frequency and signal attenuation to some local indicators. This can be under the category of the current challenges, the question is as follows, How GPR data can be converted to indicators based on the common defects in road transports. Therefore, establishing potential metrics to value GPR-related indicators in both a qualitative and quantitative approaches is crucial to provide better understanding of the defects and their propagation in road pavements.

How to cite: Rasol, M.: Towards sustainable road transport infrastructure: Insights from GPR performance indicator development and enhancement of data quality, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1641, https://doi.org/10.5194/egusphere-egu23-1641, 2023.

Groundwater is het largest available freshwater resource on earth and is critical to humans and the environment. Groundwater is especially important for irrigated agriculture, and thus for global crop production and food security; approximately 40% of the today’s irrigated agriculture depends on groundwater. In many regions around the world, unsustainable groundwater pumping exceeds recharge from precipitation and rivers. This leads to substantial drops in groundwater levels and losses of groundwater from its storage, especially in intensively irrigated regions, as well as reduction of river flows with possible devastating impacts on freshwater ecosystems.

In my research I simulate groundwater flows and groundwater surface water interactions globally, using a high resolution coupled groundwater and surface water model, and study the impacts of groundwater pumping from the recent past until the far future. In this talk I will present recent findings on current and projected impacts of groundwater pumping on river flows, including an estimate where and when environmentally critical thresholds for groundwater discharge are reached. Second, I will present novel developments and future research steps me and my team will take towards estimating global groundwater availability that can be sustainably exploited and the trade-off between sustainable groundwater use and crop production.

How to cite: de Graaf, I.: Groundwater availability and sustainability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11454, https://doi.org/10.5194/egusphere-egu23-11454, 2023.

Compound drought and hot extremes (CDHE) are periods of prolonged dry and hot weather exhibiting adverse impacts on nature and humankind than their counterparts. Understanding compound extremes is in its infancy due to complex dynamical climate systems involving interactions and feedback with the different processes at different scales. Our detailed investigation of the last seven decades of CDHE during the Indian Summer Monsoon has shown alarming observations. Our results confirmed a threefold increase in CDHE frequency for the recent period (1977–2019) relative to the base period (1951–1976), exhibiting a strong spatial pattern. Further investigation revealed CDHE likelihood, and spatial diversity in the CDHE occurrence is a function of the strong negative association between precipitation and temperature and soil moisture-temperature coupling, respectively. Investigation into the temporal evolution of CDHE confirms the strengthening of the negative association between precipitation and temperature, indicating a higher number of CDHE in future.

How to cite: Agarwal, A.: Disentangling the Characteristics and Drivers of Compound Drought and Hot Extremes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8830, https://doi.org/10.5194/egusphere-egu23-8830, 2023.

Coronal holes (CH) are large, long-lived structures commonly observed in the solar corona as regions of reduced emission in EUV and X-ray wavelengths. They feature a characteristic open magnetic field configuration along which ionized electrons and atoms are accelerated into the interplanetary space. The resulting outflowing plasma is called high seed solar wind stream (HSS; see Cranmer 2009 and references therein). These HSSs are the major cause of minor to moderate geomagnetic activity at Earth (see Richardson 2018 and references therein).

To be able to predict the arrival and impact of those disturbances accurately, their origin and evolution need to be studied in detail. And to do so, it is imperative that CHs are accurately and reliably extracted, thus leading to the development of the Collection of Analysis Tools for Coronal Holes (CATCH). By using the intensity gradient across the CH boundary, it is possible to robustly extract CHs whose properties can then be analyzed. We find that the area of long-living CHs generally evolves by growing to a maximum before decaying. However, the associated magnetic field does not evolve equally. Depending on the CH, we find a correlation, an anti-correlation or even no correlation over the course of its lifetime. Therefore, we believe that the evolution of a CHs magnetic field is primarily driven by the large-scale connectivity changes in the Sun's global magnetic field. Further, we find that the plasma properties within CHs show a significant center to boundary gradient, which may justify the distance-to-boundary parameter used in some solar wind modeling.

To study the evolution of CHs in detail, a 360° view of the Sun is necessary; however, the magnetic far-side of the Sun still eludes. The few snapshots with Solar Orbiter provide only a fragmented picture of the magnetic field on the solar far-side. We found that by using EUV observations of the transition region (specifically using Stereo) it is possible to estimate the magnetic field density of CHs on the solar far side. In addition, we are currently investigating the incorporation of helioseismic observations into synoptic magnetograms to generate a maps that show the magnetic field of the whole Sun at a given time.

How to cite: Heinemann, S. G.: On the evolutionary aspects of solar coronal holes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8687, https://doi.org/10.5194/egusphere-egu23-8687, 2023.