Anthropogenic disturbance of the nitrogen (N) cycle has more than doubled the amount of reactive N circulating in the terrestrial biosphere alone. Exchange of reactive/non-reactive nitrogen gases between land and atmosphere are strongly affecting Earth’s atmospheric composition, air quality, climate change and human health. This session seeks to improve our understanding and modelling on how global land use and climate change affect N biogeochemistry in terrestrial and aquatic ecosystems and what atmospheric interactions will be most important in influencing the climate. We seek to link microbiological N cycling processes and exchanges of nitrogen gases at the land-air interface with ecosystem dynamics, air quality and atmospheric chemistry. Despite being intensively studied for a long time, it is still difficult to predicting N transformation pathways because of our lack to quantitatively understand N cycling processes and the numerous processes contributing to (gaseous) N losses in terrestrial ecosystems. The session covers fluxes of different reactive and non-reactive nitrogen gases and the underlying transport and transformation processes in soils and sediments, e.g., fixing of atmospheric dinitrogen (N2) in ecosystems, emission/deposition of ammonia (NH3), nitric oxide (NO), nitrous oxide (N2O), nitrous acid (HONO), nitrogen dioxide (NO2), and N2 (as a result of denitrification) as well as their interactions with ozone (O3), volatile organic compounds (VOCs), free radicals and aerosols in the atmosphere, and the associated impacts on air quality. To predict processes an understanding of the soil heterogeneity is pivotal not only in surface soils and at field scale but also deeper in the soil profile and at small scales (µm). Recent technological improvements of experimental and analytical tools like measurements of N2 fluxes, linking structure and activity of functional microbial communities with flux rates, small scale resolution of soil structure, and improved numerical methods as well as computational power offer new opportunities in this area. Furthermore, the interactions of N cycling with other elemental cycles (e.g., carbon, phosphorus) in ecosystems and terrestrial-aquatic linkages, and feedbacks to biodiversity loss and water pollution will be explored. We welcome contributions covering a wide range of studies including methods development and application of new devices, observational, experimental, and modeling approaches.

The session aims at collecting contributions from all scientists daily faced with the need of discriminating between what is natural and what is the result of the interaction of humans with the surrounding environment, with respect to elemental concentrations. Commonly, geoscientists involved in environmental projects are requested to define local or regional reference concentration values for those chemical substances (mostly potentially harmful elements) and, recently, radioisotopes which can be originating from both geological materials and human driven processes.
To discriminate natural contributions from anthropogenic ones is a very complicated task and several scientists have applied different methods and multiple approaches (from statistics to the weight of evidence) in order to provide guidance and reliable solutions to government institutions and professional stakeholders.
Case studies on solid matrices (soil, sediments, etc.), natural water and other environmental media are of interest for the session together with more methodological studies mostly focusing on the proposal of innovative techniques for defining these values.

The critical zone comprises the Earth's permeable near-surface layer from the top of the canopy to the bottom of the groundwater. It is the zone where hydrosphere, atmosphere, pedosphere and geosphere interact with the biosphere. This fragile skin of our planet, which supports the life and survival of humans maintaining food production and drinking water quality, is endangered by threats such as climate change and land use change.
New approaches and innovative modeling strategies are needed to understand these complex interactions between hydrological, biogeochemical cycles and human resilience processes that may govern critical zone system dynamics, including sources, dynamics and chemistry of water, models to quantify external influences like human activities or erosion, weathering rate, water transfer in the frame of global change and biological feedback mechanisms.
This session focuses on the advancing proxies that may address pressing interdisciplinary scientific questions in coupling various disciplines like hydrology, soil science and biogeochemistry that cover single-site investigations, targeted experiments, remote sensing studies, large data compilations and modelling. This will be illustrated in this session through studies regarding the critical zone as a whole or within its different compartments, including the different environmental processes (geological, physical, chemical, and biological), their couplings and reactive transport modeling , and exploring the cities resilience.

Phosphorus (P) is essential to life, and as a key limiting nutrient, regulates productivity in terrestrial and aquatic systems. Strong geochemical interactions between P and other elements control the mobility and bioavailability of P in the environment, necessitating a coupled understanding of element cycles influencing P. At the same time P provides perhaps the most topical example of a critical resource element whose use is currently inefficiently managed. Leakage of mined P into the environment through a variety of processes (e.g. excess chemical fertiliser usage, or effluent discharges) is responsible for eutrophication and the acceleration of natural P cycling in terrestrial and aquatic systems. This puts P at the forefront of environmental and societal concerns and demands that our biogeochemical knowledge of P cycling ought to be developed through interdisciplinary research. This session aims to explore biogeochemical P cycling in the context of benefitting ‘systems understanding’ spanning terrestrial and aquatic compartments.

Topics included will explore:
Links between P and wider element cycles, for example with other macro- and micro- nutrients and controls of P availability through geochemical parameters such as Fe;
P cycling studies that bring into focus the interplay of biotic and abiotic controls within, and between, environmental compartments;
Drivers of change (climate, management, societal) acting on the coupling of P with other element cycles.
Processes, modelling and management against a background of the key issues for: P release from soil to plants; P release from soil to water; long term P supplies and the global P cycle.
Sustainable use of P, recovering of P from natural and waste water, managing P fluxes in agricultural areas.

Soils represent a major terrestrial carbon store and fulfil a variety of functions from which the environment and humankind benefit. Soils processes operate and interact across the Critical Zone: the near-surface terrestrial layer extending from the bedrock through to the lower atmosphere. Multiple external pressures may result in changes to soil functioning, and we need a good understanding of how soils respond at a range of spatial and temporal scales.

The storage, stability, and cycling of carbon is fundamental to the resilience of soil systems. It is essential that we consider the role of carbon in all soil systems, from the microbial and aggregate scale to the catchment and the whole land surface, in order to better understand the interconnectivity between rocks, soils, plants, and the atmosphere. This is particularly important as soils are facing multiple perturbations, ranging from rapid shifts in land use and management to degradation and long-term environmental and climatic change. To maintain soil functions we need to develop further knowledge of how resistant soils are to these changes, alongside if, and how, they recover.

This session will consider terrestrial carbon pools and dynamics, and explore soil resilience at any, or multiple scales. We welcome contributions that consider processes within and between different elements of the Critical Zone, alongside innovative methods of quantifying and investigating change. Early career researchers are strongly encouraged to apply, and we seek submissions considering empirical, modelling, or meta-analytical approaches.

Rationale: Progressive thawing of permafrost poses a significant threat to the stability of arctic landscapes, and has strong consequences for our climate. To predict the transition of arctic landscapes and its consequence for climate-feedback, we need to understand the dynamics of permafrost thaw. Most climate models assume a gradual, top-down thawing of permafrost, resulting in gradual decomposition of carbon and enhanced plant growth (“Arctic Greening”). However, evidence of an alternative, abrupt thawing trajectory of permafrost (“Arctic Browning”) is currently increasing across the Arctic. Consequences for landscape stability and climate feedback diverge widely between these trajectories, which emphasizes the need to understand their triggers.

Aim: In this session we aim to bring together and integrate the state-of the art on the future development of permafrost ecosystems from various disciplinary backgrounds. Thereby, we hope to improve our understanding of (i) the anticipated occurrence of various thaw phenomena under global warming, (ii) the implications of these various thaw phenomena for permafrost ecosystems and (iii) the implications of various thaw phenomena for climate feedbacks.

We have compiled an exiting programme covering mechanisms, processes and fluxes at different spatial scales, from landscape to microbe. Contributions come from accross all permafrost regions from a wide range of research institutes.

The session will be started of by professor Merritt Turetsky (incoming Director, INSTAAR at the University of Colorado Boulder) on our current knowledge and the main research gaps related to the cross-scale impacts of abrupt thaw phenomena, from local-scale changes that affect water and food security to carbon emissions and global climate. She will also discuss how permafrost thaw is interacting with other disturbance regimes such as wildfire.

A grand challenge facing society in the coming decades is to feed the growing human population in a sustainable and healthy manner. This problem is made more complex by an increasingly globalised food system and its interactions with a changing climate. Agri-food system actors - including policy makers, corporations, farmers, and consumers - must meet this challenge while considering potentially conflicting priorities, such as environmental sustainability (e.g., minimising disturbance to ecosystems via greenhouse gas emissions and the use of water, land, fertilisers and other inputs), economic viability (e.g., revenues for food producers and guaranteed access for consumers), nutritional balance and quality (e.g., addressing overconsumption and undernourishment), and resilience to climate change.
This growing complexity of agri-food systems, which can involve global supply chains and difficult environmental and societal tradeoffs, needs to be better understood.
The type of product (e.g. plant or meat based, fresh or processed), as well as the location and method of production, can play an important role in improving the nutritional quality and environmental sustainability of global food production, to enable healthy and sustainable diets. Quantifying and assessing these multiple outcomes while accounting for the linkages, interconnections, and scales of local and global supply chains will be essential for informing decisions aimed at developing sustainable and resilient agri-food systems.
This session welcomes submissions that quantify and assess a range of outcomes from agri-food systems across multiple spatial and temporal scales, and the trade-offs or synergies between them. The session will include studies providing improved methods for quantifying multiple environmental, economic or social dimensions, studies that incorporate the role of food trade into solution-development, and studies that seek to achieve multiple sustainability goals together.

The interactions between aerosols, climate, and weather are among the large uncertainties of current atmospheric research. Mineral dust is an important natural source of aerosol with significant implications on radiation, cloud microphysics, atmospheric chemistry and the carbon cycle via the fertilization of marine and terrestrial ecosystems.
In addition, properties of dust deposited in sediments and ice cores are important (paleo-)climate indicators.

This interdivision session is open to contributions dealing with:
(1) measurements of all aspects of the dust cycle (emission, transport, deposition, size distribution, particle characteristics) with in situ and remote sensing techniques,
(2) numerical simulations of dust on global and regional scales,
(3) meteorological conditions for dust storms, dust transport and deposition,
(4) interactions of dust with clouds and radiation,
(5) influence of dust on atmospheric chemistry,
(6) fertilization of ecosystems through dust deposition,
(7) any study using dust as a (paleo-)climate indicator including investigations of Loess, ice cores, lake sediments, ocean sediments and dunes.

We especially encourage to submit papers on the integration of different disciplines and/or modeling of past, present and future climates.

Public information:
Please be aware that there are a number (N=3) changes in the order in which the presentations will be discussed. Please have a look at the provided session materials for the final program.

(Bio)minerals, in particular carbonates (but also others e.g. phosphates), play an essential role in shaping our understanding of the evolution of life and the Earth System, and constitute one of the most important archives of past climatic and environmental conditions. Geochemical, petrographic or crystallographic approaches have yielded new insights into the physico-chemical conditions governing their formation, including through biomineralisation pathways. These capture vital information about the environment and fluid chemistry during precipitation in the form of their specific elemental or isotopic signatures, mineralogies or micromorphologies. Over the past decades, a refined understanding of both biogenic as well as abiotic carbonates and other mineral archives, together with the development of new analytical methods and palaeo-proxies, has led to numerous breakthroughs in palaeoclimate research. However, the quality and reliability of the climatic and environmental information we extract from these records depends, critically, on careful proxy calibrations and the evaluation of secondary controls such as kinetic or vital effects and diagenetic influences. This session seeks contributions from sedimentology, geochemistry, (palaeo)biology, and mineralogy that utilise carbonate or other relevant (bio)minerals to improve our understanding of past environmental conditions over a broad range of timescales, including (but not limited to) microbialites, mollusc shells, coral skeletons or foraminifera. We welcome experimental or theoretical studies dealing with culturing of calcifying organisms, synthetic mineral precipitation, transformation or alteration processes, elemental partitioning or isotopic fractionation (to give but a few examples). The aim of this session is to synthesize recent progress on the investigation as well as application of these important archives, and to showcase methodological advances that will help us to build a more comprehensive understanding of past global changes.

The session gathers geoscientific aspects such as dynamics, reactions, and environmental/health consequences of radioactive materials that are massively released accidentally (e.g., Chernobyl and Fukushima nuclear power plant accidents, wide fires, etc.) and by other human activities (e.g., nuclear tests).

The radioactive materials are known as polluting materials that are hazardous for human society, but are also ideal markers in understanding dynamics and physical/chemical/biological reactions chains in the environment. Thus, the radioactive contamination problem is multi-disciplinary. In fact, this topic involves regional and global transport and local reactions of radioactive materials through atmosphere, soil and water system, ocean, and organic and ecosystem, and its relation with human and non-human biota. The topic also involves hazard prediction and nowcast technology.

By combining 34 years (> halftime of Cesium 137) monitoring data after the Chernobyl Accident in 1986, 9 years dense measurement data by the most advanced instrumentation after the Fukushima Accident in 2011, and other events, we can improve our knowledgebase on the environmental behavior of radioactive materials and its environmental/biological impact. This should lead to improved monitoring systems in the future including emergency response systems, acute sampling/measurement methodology, and remediation schemes for any future nuclear accidents.

The following specific topics have traditionally been discussed:
(a) Atmospheric Science (emissions, transport, deposition, pollution);
(b) Hydrology (transport in surface and ground water system, soil-water interactions);
(c) Oceanology (transport, bio-system interaction);
(d) Soil System (transport, chemical interaction, transfer to organic system);
(e) Forestry;
(f) Natural Hazards (warning systems, health risk assessments, geophysical variability, countermeasure);
(g) Measurement Techniques (instrumentation, multipoint data measurements);
(h) Ecosystems (migration/decay of radionuclides).

The session consists of updated observations, new theoretical developments including simulations, and improved methods or tools which could improve observation and prediction capabilities during eventual future nuclear emergencies. New evaluations of existing tools, past nuclear contamination events and other data sets also welcome.

Public information:
Here is instruction of a live chat,
(1) Convener’s summary at the beginning of Chat 10:45-11:00
(2) We then go each presentation for 5 minutes including discussion.
(3) Each presenter posts their own "a few sentence summary within 80 words" in total, and the discussion. Omit any greeting to save time.
(4) To save time, we even offer to post your summary when we introduce your talk if you send me before hand
Live chat schedule
10:45 Convener summary
— we present one highlight slide from each presentation and give audience to search for presentation to deeply look into.
11:00 10066 Mykola Talerko et al
11:05 15257 Joffrey Dumont Le Brazidec et al
11:10 233 Sheng Fang et al
11:15 5844 Elena Korobova et al
11:20 2252 Misa Yasumiishi et al
11:25 13220 Yuichi Onda et al (solicited/Highlights)
11:30 13965 Fumiaki Makino et al
11:35 12301 Michio Aoyama et al
11:40 22136 Yasuhito Igarashi et al
11:45 12465 Hikaru Iida et al
11:50 19250 Mark Zheleznyak et al
11:55 12477 Yoshifumi Wakiyama et al
12:00 3175 Michio Aoyama et al (solicited)
12:05 11813 Yayoi Inomata and Michio Aoyama
12:10 12627 Daisuke Tsumune et al
12:15 21319 Susumu Yamada (Masahiko Machida) et al
12:20 6987 Hikaru Miura et al
12:25 Closing remark

The session gathers geoscientific aspects such as dynamics, reactions, and environmental/health consequences of radioactive materials that are massively released accidentally (e.g., Chernobyl and Fukushima nuclear power plant accidents, wide fires, etc.) and by other human activities (e.g., nuclear tests).

In addition to hazardous aspect for human society, the radioactive materials are used as ideal markers in understanding dynamics and physical/chemical/biological reactions chains in the environment. This multi-disciplinary session gathers all these aspect.

Climate change is projected to result in an increase in extreme and compound weather events, which pose a growing threat to human well-being and the achievement of the UN Sustainable Development Goals (SDGs). Further warming is also projected to reduce the efficacy of carbon sinks acting as negative feedbacks on warming and increase the risk of crossing tipping points and triggering cascading changes in the climate and ecosystems. These processes may reduce the Earth system’s resilience, which has the potential to further amplify climate change and extremes and worsen societal impacts.

Maintaining Earth in the Holocene-like conditions that have enabled the development of the world’s societies will require better understanding of feedbacks and tipping dynamics in both the human world and the biophysical Earth. Societies will need to embark on rapid socio-economic and governance transformations in order to both reduce the risk of triggering tipping points and to improve societal resilience to increasingly likely extreme events. Earth resilience brings the complex dynamics and perturbations associated with human activities into Earth system analysis, and increasingly captures socio-economic as well as biophysical dynamics.

In this session we welcome transdisciplinary and cross-scale contributions relating to climate extremes, tipping dynamics, and Earth resilience, covering topics ranging from the cascading impacts of extreme and compound events, key feedbacks and tipping points in both biophysical and human systems, enhancing societal resilience to extreme events, and the potential for rapid social transformations to global sustainability.

Public information:
EGU 2020 Session TS3.2/NH10.7
Climate Extremes, Tipping Dynamics, and Earth Resilience in the Anthropocene
6 May, 14:00-18:00

This session will run as an EGU website hosted text-based chat accessible here, as well as through a simultaneous Zoom video room (link to be provided during the livechat).

Both the EGU chatroom and the Zoom video room will be moderated.
Comments on the presentations can be made at the EGU website at any time, for asynchronous responses.
Comments and questions asked in the EGU chatroom will be forwarded to the Zoom presenters. This means all questions will get responses, but this may not happen within the timeslot of the presentation.
To facilitate real-time dialogue with the presenters, please go to the Zoom session.

When joining the Zoom session remember to mute yourself, and to ask questions please raise your hand (available from the 'participants' button) and unmute when the chair calls on you. If you are a presenter, unmute when called on and share your screen if you have a few slides to show. Each presenter gets 10 minutes max including Q&A, so we suggest presenting some summary slides for a few minutes and then taking questions for the rest.

Remaining carbon budgets specify the quantity of CO2 that can be emitted before a given warming level (such as the 1.5 °C target) is reached, and are thus of high interest to the public and policymakers. Yet, there are many sources of uncertainty which make it challenging to deduce this finite amount of CO2 emissions. The theoretical foundation of carbon budgets is based on the concept of the Transient Climate Response to cumulative CO2 Emissions (TCRE). This is the pathway-independent ratio of global warming per unit of cumulative CO2 emissions. However, accounting for non-CO2 forcings and changes in albedo or other Earth system feedbacks provides further challenges in calculating TCRE and the remaining carbon budgets.

This session aims to further our understanding of the climate response under different emission scenarios, and to advance our knowledge of associated carbon budgets consistent with meeting various levels of warming. We invite contributions that use a variety of tools, including fully coupled Earth System Models, Integrated Assessment Models, or simple climate model emulators. We welcome studies exploring different aspects related to carbon budgets and the TCRE framework, including: the governing mechanisms behind linearity of TCRE and its limitations, effects of different forcings and feedbacks (e.g. permafrost carbon feedback) and non-CO2 forcings (e.g. aerosols, and other non-CO2 greenhouse gases), estimates of the remaining carbon budget to reach a given temperature target (for example, the 1.5 °C warming level from the Paris Agreement), the role of pathway dependence, the climate-carbon responses to different emission scenarios (e.g. SSP scenarios, or idealized scenarios), and the behaviour of TCRE in response to artificial CO2 removal from the atmosphere (i.e. negative emissions). Contributions from the fields of climate policy and economics focused on applications of carbon budgets are also encouraged.

To showcase their strong thematic connection, the two sessions “Air-Land Interactions (General Session)” and “Understanding and Characterization of Land-Atmosphere Feedback” were merged.

The session is addressed to experimentalists and modellers working on land surface fluxes from local to regional scales. The programme is open to a wide range of new studies in micrometeorology. The topics include the development of new devices, measurement techniques and experimental design methods, as well as novel findings on surface layer theory and parametrization at the local scale. The theoretical parts encompass soil-vegetation-atmosphere transport, internal boundary-layer theories and flux footprint analyses, etc.. Of special interest are comparisons of experimental data, parametrizations and models. This includes energy and trace gas fluxes (inert and reactive) as well as water, carbon dioxide and other GHG fluxes. Specific focus is given to outstanding problems in land surface boundary layer descriptions such as complex terrain, energy balance closure, stable stratification and night time fluxes, as well as to the dynamic interactions with atmosphere, plants (in canopy and above canopy) and soils including the scale problems in atmosphere and soil exchange processes.

The understanding of feedback processes in the land-atmosphere (L-A) system is crucial for advanced modeling and prediction of weather and climate. However, the impact of soil moisture and evapotranspiration on the diurnal cycle of the planetary boundary layer (PBL), clouds, and precipitation remains a sore gap in our understanding of weather processes and climate statistics. For this purpose, the exchange of momentum, water, energy, and carbon at the land surface and at the top of the PBL has to be investigated from the local to regional scales in great detail. In this session, we accept observational and modeling approaches to address these challenges. With respect to the observations, emphasis is put on the application of new sensor synergies for studying L-A exchange processes and entrainment at the PBL top based on long-term data sets or recent field campaigns, e.g., combining multi-tower, scanning lidar, airborne, and satellite observations. With respect to theoretical understanding and modeling, we welcome the study of feedback processes as well as the derivation and application of feedback metrics from the mesoscale to turbulent scales, e.g., derived by large eddy simulations.

The dynamics of the solid Earth and its surface are strongly affected by their interplays as well as biota and climate. These constant feedback systems operate at a variety of spatial and temporal scales that are regulated in a complex system of interactions. For instance, in the critical zone -the terrestrial surface environment ranging from the lower atmosphere to the solid parent material- interplays not only regulate manifold ecosystems and bio-geochemical cycles, but also shape the Earth’s surface at the interface between atmosphere and lithosphere, where soils develop. At much larger scales, plate tectonics and global geodynamics control the physiography, climate and hydrosphere, which in turn strongly affect the surface feedback processes via tectonic, biological, geochemical and hydrological processes. Ultimately, climate and tectonics are prominent macro-ecological drivers of landscape development. But even though the underlying geology and tectonic processes have long been recognized as driving parameters, this is much less so for biological processes. The driving force of microorganisms, plants and animals on the shape of land surfaces is still poorly understood.
Understanding the links between the solid Earth and the external spheres of the Earth has experienced a recent upswing due to advanced analytical techniques, but also thanks to fostered interactions between researchers from different disciplines. This session aims to bring together geoscientists, soil scientists, climatologists and biologists working at different spatial and temporal scales on the feedback interactions between geology, topography, soils, climate and biosphere at the surface of the Earth. The session covers a multitude of topics from the microbial to the geodynamics time and space scales.

Solicited speakers are:
Carina Hoorn, University of Amsterdam, The Netherlands
Alexia Stokes, French National Institute for Agricultural Research – INRA, France
Veerle Vanacker, University of Louvain, Belgium