Scientific sessions

Conveners

Daniel Rasche (GFZ, Potsdam), Laurent Longuevergne (Géosciences, Rennes), Ulrike Werban (UFZ, Leipzig), Julie Albaric (Chrono-Environnement, Besançon)

Description

Access to informative observation is a pre-requisite to understand how linkages between geological, biological and hydrological cycles defines the critical zone. This thin and highly heterogeneous layer of the Earth extends from the land surface, including vegetation and water bodies, through the pedosphere and the unsaturated zone to the groundwater. The challenges consist in obtaining adequate representations of landscape spatial heterogeneity to inform bottom-up modeling approaches, or to design and perform integrated measurements to meaningfully constrain top-down modeling approaches. Several data sources are rarely used or poorly exploited in critical zone studies. These include new types of data that are still under investigation, as well as traditional types of data (e.g. results of fieldwork investigations, maps of various characteristics of the landscape) that are seldom used to a full degree in larger scale studies for various reasons, such as incommensurability problems and inadequate models.

This session will focus on how data obtained from new observation techniques and from innovative analysis of existing data sources can be used to inform model design and process identification at larger scales. We solicit contributions related but not limited to:

(i) Innovative sensing and experimental techniques to advance understanding of the critical zone (e.g., wireless distributed sensing, cosmic-ray neutron sensing, hydrogeophysical methods, fiber optics, tracing methods, etc.). We also encourage submissions of works focusing on new instrumental techniques and developments with strong potential to widen points of views (microbiology, citizen science, etc.) and update approaches (energetic and teletransmission challenges, etc.).

(ii) Methods for the evaluation, visualization, and interpretation of monitoring and experimental data sets from multiple sources to maximize the information gained from critical zone observatories. Thus, we encourage submissions of works dealing with model-data fusion including new concepts for joint and coupled inversion.

(iii) Analysis of spatial and temporal patterns of critical zone properties and processes at different scales (e.g., source deconvolution for hot moments/hot spots identification).

(iv) Unusual and unexpected critical zone phenomena identified by measurements that seem to defy current understanding of the critical zone. Such phenomena could have been observed in the field or in the laboratory. Contributions focusing on the understanding of linked hydrological, geophysical properties and or geochemical processes are highly welcome.

Keynote speaker

Conveners

Steffen Zacharias (UFZ, Leipzig), Thomas Pütz (FZ Jülich), Jérôme Gaillardet (IPGP, Paris)

Description

Climate change and anthropogenic activities affect the sustainability and resilience of our environment at different scales. In order to assess the impact and complexity of climate change and diverse anthropogenic activities on the different areas of our environment, research approaches need to be designed at spatial and temporal scales. Current research needs to address these challenges and pursue conceptually innovative approaches that pursue interdisciplinary concepts as long-term investigations.

In this session, long-term observations of terrestrial research areas will be presented, covering the broad spectrum from purely hydrological/physical/chemical methods to socio-ecological approaches. The different compartments or geo-hydro-atmospheric and socio-ecological "spheres" will be addressed. Different scientific disciplines use their specific perspectives and observation strategies: observing compartments at different scales, monitoring key parameters, using model-data interactions, and involving stakeholders.

In this session we want to compare the different perspectives, research approaches and initiatives for an integrative approach to terrestrial ecosystem monitoring. We invite contributions on scientific approaches and the design of observatories and observatory networks that monitor the human environment and the pronounced changes that our environment is undergoing in the Anthropocene. We particularly welcome contributions on the challenge of upscaling local observations to continental observations.

Keynote speaker

Conveners

Carsten Montzka (FZ Jülich), Jian Peng (UFZ, Leipzig), Manuela Grippa (GET, Toulouse), Gilles Boulet (CESBIO, France)

Description

The critical zone is spatially heterogeneous and highly dynamic in time, exchanging heat, momentum, water and nutrients at different scales. Remote sensing can be used to understand related key land surface properties, patterns, and processes. In this session, we invite contributions that employ remote sensing on various platforms to gain knowledge about different land and water cycle variables of the critical zone . The topics may include, but are not limited to:

• Retrieval and analysis of land surface parameters describing vegetation, hydrology, energy, and nutrient patterns.
• Investigation of fluxes and processes between different land surface compartments and feedbacks.
• Analysis of extreme events such as floods and droughts with support of remote sensing.
• Utilization of remote sensing data from various platforms (UAVs, airborne, spaceborne).
• Implementation of various sensor types such as multispectral or hyperspectral optical sensors, SARs, LiDARs, optical and radar altimeters, and thermal sensors as well as their combinations.
• Approaches to improve the spatial, spectral, radiometric, and temporal resolutions of remote sensing data for the analysis of land surface properties, patterns, and processes.
• Combination of remote sensing with in situ data or model systems to gain knowledge about unmonitored compartments.
• Implementation of different statistical, physical, and machine learning methods with remote sensing data to understand the soil-vegetation-atmosphere dynamics.

Keynote speaker

Conveners

Pierre Sabatier (EDYTEM, Le Bourget du Lac), Cecile Blanchet (GFZ, Potsdam), Ingo Heinrich (DAI German Archaeological Institute, Berlin), Markus Schwab (GFZ, Potsdam)

Description

Critical zone processes and their driving mechanisms including climate forcing (temperature, precipitation) and human impacts (pollution, agriculture, erosion) operate on a variety of time and space scales. Instrumental measurements, however, are only available for a limited time period and thus cannot describe the entire potential variability. Proxy data from various biological and geological archives have demonstrated that climate variability and environmental changes can be reconstructed even on seasonal to millennial time scales. The quantitative exploitation of proxy data in terms of critical zone processes and related forcings can be improved by a better understanding of the signal transfer into the different geoarchives (e.g., lake sediments, tree rings, speleothems). Ideally, this is achieved by integrating modern observation/monitoring and recent well dated proxy records. This approach leads to a sophisticated proxy interpretation allowing for an advanced assessment of ongoing changes in the Critical Zone based on longer time perspectives.

This session aims to address specific problems of research at the interface of instrumental and proxy time scales, for example, the different temporal resolutions of data. We want to encourage discussions among researchers from different disciplines trying to elaborate a long term integrative understanding of Critical Zone trajectories under the influence of different drivers. We especially welcome contributions on monitoring of proxy data formation to develop a retro-observation of Critical Zone processes: synchronization and dating of proxy data time series from different natural archives, investigating the impacts and interactions of landscape forming and Critical Zone processes, combining high resolution archives with other data sources such as meteorological data, remote sensing data, historical information aiming at a comprehensive understanding of landscape evolution and Critical Zone processes, the use of landscape evolution models for hypothesis testing.

Keynote speaker

Conveners

Camille Bouchez (Géosciences, Rennes), Jean Marçais (RiverLy, Lyon), Theresa Blume (GFZ)

Description

Catchments dynamically store and release water, which is critical for ecosystem sustainability and water supply in the Anthropocene. However, challenges remain in: i) quantifying water partitioning in the different compartments of the critical zone (vegetation, vadose zone, shallow or deep groundwater) and the associated water and matter transit times, and ii) predicting the hydrological response to changes in climate forcing and anthropogenic transformation (land use change, intensive agriculture). This session seeks to provide a deeper understanding of the variability of hydrological processes both in time and space, to support sustainable water resource management in the face of evolving anthropogenic and climatic challenges.

This session aims to highlight recent advances, innovations, and emerging methods to monitor and model catchment water dynamics. We encourage contributions that develop novel geophysical experiments, multi-tracer investigations, or high-frequency environmental sensing. We also welcome studies that explore fundamental descriptors of catchment water storage and dynamics, through integrated hydro(geo)logical modelling or storage selection function approaches. Finally, this session will provide an overview of the current knowledge gaps and research priorities related to the measurement and modelling of water dynamics.

Keynote speaker

Conveners

Daniel Graeber (UFZ, Magdeburg), Ophélie Fovet (INRAE SAS, Rennes)

Description

Catchment-scale and landscape-scale biogeochemical patterns are the result of a multitude of processes, especially critical-zone processes at the interfaces between the atmosphere, soils, the terrestrial biosphere, and the hydrosphere. At these interfaces, essential processes occur for the transformation, transfer, and storage of organic and inorganic compounds, such as organic carbon and nutrients. Moreover, climate change and land-use change affect the biogeochemical processes of water, carbon, and nutrients at these interfaces. Too often, however, biogeochemical processes have been studied in only one (e.g., soils, including the rhizosphere, plant roots, soil organisms, and soil solution) or two (e.g., vegetation and soil) components of the critical zone, in isolation from the atmosphere and hydrosphere. Moreover, process research at critical zones often does not consider the resulting effects on a broader spatial and temporal scale.

This session invites contributions that will enhance our understanding of biogeochemical patterns at large scale, especially with links to critical-zone processes. Contributions on biogeochemical cycles involving soluble elements but also on particulate matter and gas exchange are encouraged. A particular focus of the session should be on key drivers of element retention and cycling (such as stoichiometry, residence times, and connectivity between compartments or ecosystems). Research contributions that use new methods and experimental techniques such as novel data-science approaches for monitoring data, high-frequency or non-invasive sensors for long-term monitoring, as well as molecular or isotopic constraints, are particularly welcome.

Keynote speaker

Conveners

Ralf Kunkel (FZ Jülich), Jan Bumberger (UFZ), Isabelle Braud (RiverLy, Lyon), Sylvain Grellet (BRGM, Orléans)

Description

Together with the rapid development of sensor technologies and the implementation of environmental observation networks, a large number of data infrastructures, implementing FAIR (Findable Accessible, Interoperable and Reusable) principles, are being created to manage and provide access to observation data. These data are necessary to provide significant advances in Earth System understanding and modeling and to progress towards models with predictive power concerning the evolution of the Earth System. However, data collected in the observatories as well as their management are often very heterogeneous, rendering a better and easier integration of data from distributed infrastructures more complex. A better use of data strongly depends on the capabilities of dealing with fast growing multi-parameter data of heterogeneous sources and on effort employing data science methods, adapting new algorithms, developing data pipelines tailored to specific scientific needs and developing interoperability between heterogeneous systems to favor multidisciplinary research. The development of methods for the automatic real-time processing and integration of observation data in models is also required in many applications. Automated quality assessment/control pipelines, data discovery and exploration tools, standardized interfaces and vocabularies as well as data exchange strategies and security concepts are required to interconnecting distributed data infrastructures that meet FAIR and open science criteria. This session focuses on the specific requirements, techniques and solutions to process, provide and couple FAIR observation data from interoperable distributed infrastructures and to make observation data available for modelling and other interdisciplinary scientific needs.

Keynote speaker

Conveners

Guillaume Nord (IGE, Grenoble), Andreas Musolff (UFZ, Leipzig), Ute Weber (UFZ)

Description

The quantity and quality of freshwater is threatened by anthropogenic impacts and climate change. Manifestations of climate change such as floods and droughts have strong impacts on landscape water partitioning, flowpaths and biogeochemical processing, and can exacerbate water quality problems .

In this session, we will explore monitoring and modelling physical processes responsible for floods, droughts and focus on specific aspects of extreme hydrologic conditions: overland flow, erosion and sediment transport, intermittent streams, groundwater recharge, and the groundwater- surface water interface.

Water erosion and sediment transport can cause natural hazards, soil degradation and threaten water quality and ecosystem health. Stream intermittency is sensitive to hydrologic extremes, and recent drought years have shown to be increasingly common even in wet areas with relatively stable flow conditions threatening aquatic ecosystems formally unexposed to these dry-ups. Here, the role of this drying and rewetting on stream- aquifer exchange, groundwater recharge, and turnover of nutrients and contaminants remains largely unexplored. Finally, the groundwater-surface water-interface, with its heterogeneous and dynamic hydrogeophysical functioning and biogeochemical reactivity, is likely to be sensitive to extremes.

Observatories such as OZCAR and TERENO can contribute to a better understanding of hydrological extremes in the critical zone. We encourage contributions to this session that focus on monitoring, conduct field and laboratory experiments, or use data-driven or numerical models from these well-studied observatories to contribute to that understanding.

Keynote speaker

To be determined.

Conveners

Agnès Rivière (Mines Paris - PSL, Paris), Claudia Schütze (UFZ, Leipzig), Julian Klaus (University of Bonn)

Description

The interactions between surface and groundwater, including the vadose zone and the surface water grourndwater interfaces, are critical process for understanding the quantitative and qualitative regimes of dependent hydrosystems. A multi-scale approach combining cross-disciplinary techniques can significantly reduce uncertainties and provide an optimal understanding of these exchanges. This session aims to showcase contributions that highlight such studies, which enhance our understanding of water fluxes within the interfaces between the surface and the groundwaters and their crucial role in energy and material cycles.

We invite presentations that address key research questions, such as:

(i) How do components across different scales—from the vertical column, including the atmosphere, vegetation, soil, and bedrock, to large-scale hydrosystems, spanning headwaters and 2D hillslopes, and from surface waters and the vadose zone to the deeper limits of groundwater—interact and interconnect?

(ii) How can we bridge the gap between rapid subsurface and slow groundwater flow processes with longer-term environmental changes that collectively shape the critical zone?

(iii) What are the potential consequences of climate warming, extreme weather events and the multifunctional usage of landscapes on groundwater recharge, discharge processes, and water quality?

This session aims to bring together researchers and scientists from diverse backgrounds to advance our understanding of groundwater’s role in the critical zone. We seek to illustrate how combining observations and numerical experiments can help delineate future predictions for hydrosystems under various climate and land-use evolution scenarios.

Keynote speaker

Conveners

Alexandre Belleflamme (FZ, Jülich), Catherine Ottlé (LSCE, Gif-sur-Yvette),

Description

Earth System models are key in understanding and assessing the impact of climate and land use on the functioning of the Earth system and its compartments. They allow making predictions and projections of the future evolution of the Earth system and the water and biogeochemical functioning of the land surface. They provide the scientific basis for designing mitigation and adaptation strategies to climate change. Still these models show considerable uncertainty in quantifying water and biogeochemical fluxes. This is caused by both the uncertainty in process descriptions and the parameterization of the land surface and the uncertainty introduced by the still limited database for development, calibration and validation. In this session we seek contributions that aim at improving the description of the land surface and specifically the critical zone in Earth System models and their compartment models (land surface models, hydrological models, etc.), with a specific focus on water and carbon.

Keynote speaker

Conveners

Ralf Kiese (KIT IMK-IFU Garmisch-Partenkirchen), Isabelle Gouttevin (CEN, Grenoble), Christoff Anderman (Géosciences Rennes)

Description

Global change has triggered several transformations, such as alterations in climate, land productivity, water resources, natural hazards and atmospheric chemistry, with far reaching impacts on ecosystem functions and services. Finding solutions to climate and land cover change-driven impacts on our terrestrial environment is one of the most important scientific challenges of the 21^st century, with interlinkages to the socio-economy. A global hot spot of climate change are mountain areas, such as the European Alps and preAlps, which have been exposed to more intense warming compared with the global average trend and to higher frequencies of extreme hydrological events, such as droughts and intense rainfall. The mountain cryosphere as a whole is profoundly altered by these changes, which manifests through a recession of the snow cover, glacier extent and volumes, and rapid permafrost degradations. This session will focus on meteorological, hydrological, biogeochemical and biodiversity interactions as well as feedback mechanisms in mountain critical zones such as:

• ecological and hydrological consequences of deglaciation, permafrost and snow cover change,
• alteration of weathering, erosion, rockfall, landslides and avalanche processes operating under vegetation, cryosphere and/or climate change,
• alteration of water, energy and matter (CO₂, other GHGs) exchange influencing ecosystem functions such as C and N storage, nutrient and water retention as well as productivity and biodiversity.

Keynote speaker

Conveners

Harrie-Jan Hendricks Franssen (FZ Jülich), Claire Lauvernet (RiverLy, Lyon)

Description

While model simulations are important to achieve information on the dynamic evolution of important critical zone variables at different spatial scales (e.g., soil carbon pools, vegetation status), they are affected by imperfect process description and unknown parameters. Measurements of critical zone variables are helpful to improve those models and predictions with them. This session focuses on model-data fusion (also called data assimilation) methods to increase our understanding of processes in the critical zone, to achieve better simulations, including for example predictions at the short or medium time scale (e.g., soil moisture evolution the next weeks), better seasonal predictions (e.g., availability of water resources or crop yield), better projections at the climate scale (e.g., impact of global change on water resources or vegetation), improved reconstructions of past states (reanalyses) or assessment of current conditions. We ask for presentations that highlight experiments with model-data fusion methods (e.g., hybrid parameter estimation-machine learning approaches), the evaluation of the value of data types to improve process understanding and model predictions (e.g., evapotranspiration measurements) or the impact of a new process description in a model (e.g., better representation of human management in land surface models) verified with measurement data. Both synthetic experiments and real-world applications are interesting for this session.

Applications can be in different research areas related to the critical zone like soil science, hydrology, ecology, land surface modelling or terrestrial systems modelling and at very different time scales ranging from reanalyses, short term predictions to future projections. Presentations could focus on model-data fusion methods like inverse modelling, data assimilation, machine learning approaches,statistical approaches, and hybrid methodsto increase understanding in model simulations and measurements.

Keynote speaker

Conveners

Julien Bouchez (IPGP, Paris), Susanne Liebner (GFZ)

Description

Interactions between mineral phases and living organisms affect in multifold ways the composition, organization, functioning, and evolution of the Critical Zone. This includes biological, chemical and physical weathering of the rock and soil formation, thus shaping pathways of element and water fluxes from deep aquifers and subsurface biosphere to the soil/plant system and development of the vegetation cover. This has broad impacts on surface and subsurface landscape shaping and atmospheric composition over geological time scales but also on quality of the soil and water resources at much shorter time scale. The aim of the session is to try to decipher the interactions between the mineral/soil compartments and the structure and functioning of the ecosystems and their biota. We invite submissions from a wide range of spatial scales, for example from the mineral/molecule interface to the ecosystem scale, and using interdisciplinary approaches. Contributions may deal with the influence of biological processes and/or organic compounds on the weathering reactions, secondary mineral and soil formation processes including aggregation as well as on the formation of flow paths. We particularly welcome contributions on the developments of biotic or abiotic tracers, investigations on processes and rates of mineral/biota interactions as well as their consequences on biogeochemical and water cycles, and feedbacks between those processes and the structure and functioning of the Critical Zone, from the subsurface rocks to the soil and ecosystems.

Keynote speaker

Conveners

Harald Kunstmann (KIT IMK-IFU, Garmisch-Partenkirchen), Nanée Chahinian (HSM, Montpellier), Laurie Boithias (GET, Toulouse)

Description

The subtropical and tropical zones, such as Sahel, Southeast Asia, etc., are vulnerable to global change: population growth, land use change, climate change, pressure on water resources and more frequent extreme events. The delineation of adaptation strategies requires an improved system understanding of the intertwined water, energy and biogeochemical cycles across the atmosphere, the land and aquatic ecosystems, and the subsurface. Their modification due to climate and local land use change needs to be assessed, as well as the impacts of societal changes on the critical zone. Scientifically sound options for improved climate resilience through smart land use, adaptation of infrastructure and housing, as well as water management need to be derived. This requires the development of suitable modelling approaches and the combination of model systems with in situ and satellite derived observations. There is the clear need for improved climate observation systems and land surface observations. Approaches need to consider particular challenges arising from the general data scarcity and poor technical infrastructure of these regions. Digital data rescue efforts need to be initiated. Strategies for the realisation of long term observations and operation of infrastructure are mandatory. Joint international efforts for knowledge transfer and capacity building need to be enforced. We invite contributions addressing these multiple scientific, technical and societal challenges.

Keynote speaker

Conveners

Nolwenn Lesparre (ITES, Strasbourg), Sylvain Kuppel (GET, Toulouse), GFZ (contact Teresa Blüme)

Description

Critical zone studies emerged by breaking boundaries through disciplines in geosciences and encouraging integrative research considering as a whole the thin skin supporting terrestrial life. Through cross-communities observations and modelling, critical zone work provides tools to better understand the interactions at play on continental surfaces and to project how human activities are altering the balance and health of life-sustaining systems. Indeed, the term "critical" is also subjective in making the critical zone an object of care and concern for the scientists studying it. As such, this definition goes beyond the traditional value-free and politically neutral approach to scientific knowledge, and is much in line with societal expectations of actionable Science in the turmoil of the Anthropocene. Still, political decisions overwhelmingly fall short of addressing the many dimensions of unsustainable environmental changes documented by critical zone research and often highlighted by popular activism reclaiming sustainable, democratic, and inclusive practices. Are the missing links only about geoscientific knowledge? From positioning research projects to secure funding, through data collection and modelling, to the dissemination of the obtained results, our critical zone research also already impacts our object of study. How to assess and reduce the ecological footprint of critical zone research, as to show exemplary pathways for other institutions? How can critical zone research further engage with civil society, stakeholders and policymakers to co-construct research questions and practices with them?

For this session, we invite contributions presenting lines of thought, initiatives, or accomplished studies to highlight ways to reinvent our research practices. Interdisciplinary work, spanning fields like philosophy, history, sociology, and their application to science or broader societal aspects, is highly encouraged. Selected works will be presented as posters, since we propose to keep the usual presentation time for a reflexive workshop. During that time, we will work on how to build the problematic to solve and launch new projects hand in hand with inhabitants, stakeholders, and policymakers. We will also reflect on our scientific positioning to achieve considering equally expert and experiential knowledge to address those living beings and sources of life disturbed by anthropogenic activities.

Keynote speaker