The increasing availability of remotely sensed observations and computational capacity, drive modelling and observational glacier studies towards increasingly large spatial scales. These large scales are of particular relevance, as they impact policy decisions and public discourse. In the European Alps, for instance, glacier changes are important from a touristic perspective, while in High Mountain Asia, glaciers are a key in the region’s hydrological cycle. At a global scale, glaciers are among the most important contributors to present-day sea level change.

This session focuses on advances in observing and modelling mountain glaciers and ice caps at the regional to global scale. We invite both observation- and modelling-based contributions that lead to a more complete understanding of glacier changes and dynamics at such scales.

Contributions may include, but are not limited to, the following topics:
• Observation and modelling results revealing previously unappreciated regional differences in glacier changes or in their dynamics.
• Large-scale impact studies, including glacier contribution to sea level change, or changes in water availability from glacierised regions.
• Advances in regional- to global-scale glacier models, e.g. inclusion of physical processes such as ice dynamics, debris-cover effects, glacier calving, or glacier surging.
• Regional to global scale process-studies, based on remote sensing observations or meta-analyses of ground-based data.
• Strategies to facilitate or systematise the information flow of observations into models (e.g. blending/homogenisation of different remote sensing products, machine learning algorithms, inverse techniques, data assimilation).
• Inverse modelling of subglacial characteristics or glacier ice thickness at regional scales.

Glaciers and ice caps are major contributors to sea-level rise and have large impacts on runoff from glacierized basins. Major mass losses of glaciers and ice caps have been reported around the globe for the recent decades. This is a general session on glaciers outside the Greenland and Antarctic ice sheets, emphasizing their past, present and future responses to climate change. Although much progress in understanding the link between glaciers and climate and the impacts of their wastage on various systems has recently been achieved, many substantial unknowns remain. It is necessary to acquire more direct observations, both applying novel measurement technologies and releasing unpublished data from previous years, as well as combining in situ observations with new remote sensing products and modelling. In order to improve our understanding of the processes behind the observed glacier changes, the application of models of different complexity in combination with new data sets is crucial. We welcome contributions on all aspects of glacier changes – current, past and future – based on field observations, remote sensing and modelling. Studies on the physical processes controlling all components of glacier mass balance are especially encouraged, as well as assessments of the impact of retreating glaciers and ice caps on sea-level rise, runoff and other downstream systems.

Process understanding is key to assessing the sensitivity of glacier systems to changing climate. Comprehensive glacier monitoring provides the base for large-scale assessment of glacier distribution and changes. Glaciers are observed on different spatio-temporal scales, from extensive seasonal mass-balance studies at individual glaciers to decadal assessments of glacier mass changes and repeat inventories at the scale of entire mountain ranges. Internationally coordinated glacier monitoring aims at combining in-situ measurement with remotely sensed data, and local process understanding with global coverage. We invite contributions from a variety of disciplines, from tropical to polar glaciers, addressing both in-situ and remotely sensed monitoring of past and current glacier distribution and changes, as well as related uncertainty assessments. A special focus of this session shall be on (i) strengths and limitations of different types of satellite data for regional and global assessments, (ii) achieving a better temporal resolution of regional and global assessments, (iii) how to develop in-situ networks for real-time monitoring of glacier changes, and (iv) advances in studies on local process understanding and how best to combine them with regional to global change assessments.

Geophysical and in-situ measurements provide important baseline datasets, as well as validation for modelling and remote sensing products. They are used to advance our understanding of firn, ice-sheet and glacier dynamics, sea ice processes, changes in snow cover and snow properties, snow/ice-atmosphere-ocean interactions, permafrost degradation, geomorphic mechanisms, and changes in en-glacial and sub-glacial conditions.

In this session, we welcome contributions related to a wide spectrum of methods, including, but not limited to, advances in radioglaciology, active and passive seismology, geoelectrics, acoustic sounding, fibre-optic sensing, GNSS reflectometry, signal attenuation, and time delay techniques, cosmic ray neutron sensing, ROV and drone applications, and electromagnetic methods. Contributions can include  field applications, new approaches in geophysical or in-situ survey techniques, or theoretical advances in data analysis processing or inversion. Case studies from all parts of the cryosphere, including snow and firn, alpine glaciers, ice sheets, glacial and periglacial environments, permafrost and rock glaciers, or sea ice, are highly welcome.

The focus of the session is to share  experiences in the application, processing, analysis, and interpretation of different geophysical and in-situ techniques in these highly complex environments. We have been running this session for more than a decade and it always produces lively and informative discussion.

This interdisciplinary session brings together modellers and observationalists to present results and exchange knowledge and experience in the use of data assimilation in the cryospheric sciences such as inverse methods, geostatistics and machine learning. In numerous research fields it is now possible to not only deduce static features of a physical system but also to retrieve information on transient processes between different states or even regime shifts. In the cryospheric sciences a large potential for future developments lies at the intersection of observations and models with the aim to improve prognostic capabilities in space and time. Compared to other geoscientific disciplines like meteorology or oceanography, where techniques such as data assimilation have been well established for decades, in the cryospheric sciences only the foundation has been laid for the use of these techniques, one reason often being the sparsity of observations. We invite contributions from a wide range of methodological backgrounds - from satellite observations to deep-looking geophysical methods and advancements in numerical techniques - and research topics including permafrost, sea ice and snow to glaciers and ice sheets, covering static system characterisation as well as transient processes.

Recent advances in machine learning (ML), data science and big data analytics have allowed new insights into cryospheric systems. A wealth of geospatial data, an abundance of satellite imagery and easy accessibility to computational power enable new potentials for data processing and analysis but also bring new challenges including data management, algorithmic efficiency and interpretation of results. Current developments in ML and data science demonstrate advances in cryospheric research by predicting future sea ice and glacier evolution, detecting permafrost features from satellite imagery, tracking intra-annual dynamics of glacier termini and mapping changes in supraglacial lake extents from SAR imagery, to only name a few developments with many more to come. In this session we invite contributions that apply novel ML and data science techniques and approaches on large datasets revealing new insights into ice sheets, glaciers and sea ice that would otherwise not be achievable using traditional methods. This includes, but is not limited to, studies using ML and artificial intelligence, advanced statistics, large-scale glacier modelling, big data analytics and innovative computing solutions. Moreover, we welcome discussions of how or if these techniques can be applied or adapted to other areas of cryospheric science to foster future collaboration amongst contributors.

Unsupervised, supervised, semi-supervised as well as reinforcement learning are now increasingly used to address Earth system-related challenges for the atmosphere, the ocean, the land surface, or the sea ice.
Machine learning could help extract information from numerous Earth System data, such as in-situ and satellite observations, as well as improve model prediction through novel parameterizations or speed-ups. This session invites submissions spanning modeling and observational approaches towards providing an overview of state-of-the-art applications of these novel methods for predicting and monitoring the Earth System from short to decadal time scales. This includes (but is not restricted to):
- The use of machine learning to reduce or estimate model uncertainty
- Generate significant speedups
- Design new parameterization schemes
- Emulate numerical models
- Fundamental process understanding

Please consider submitting abstracts focused on ML applied to observations and modeling of the climate and its constituent processes to the companion "ML for Climate Science" session.

Snow constitutes a freshwater resource for over a billion people world-wide. High percentage of this water resource mainly comes from seasonal snow located in mid-latitude regions. The current warming situation alerts that these snow water storages are in high risk to be dramatically reduced, affecting not only the water supply but also the ecosystem over these areas. Therefore, understanding seasonal snow dynamics, possible changes and implications have become crucial for water resources management. Remote sensing has proven to be the main technique used to monitor the snow properties across mid-large extensions and their hydrological implications, for decades now. Moreover, the recent advances, which are mainly focused on the study of snow properties at higher spatio-temporal scales (e.g., small-scale snow-topography interactions, snow-vegetation interaction, diurnal variation of snow, rain over snow events), are helping to understand better snow accumulation, distribution and ablation dynamics.
This session is focused on studies linking the use of remote sensing of seasonal snow in hydrological applications: techniques and data from different technologies, such as time-lapse imagery, laser scanners, radar, optical photography, thermal and hyperspectral technologies, or other new applications, with the aim of quantifying and better understanding snow characteristics (i.e. snow grain size, snow depth, albedo, pollution load, snow specific area and snow density), snow related processes (snowfall, melting, evaporation and sublimation), snow dynamics, snow modelling, snow hydrological impacts and snow environmental effects. Works covering different spatial scales, from the plot to the global, and temporal scales, from instantaneous to multiyear, are welcome.

Our planet is shaped by a multitude of physical, chemical and biological processes. Most of these processes and their effect on the ground’s properties can be sensed by seismic instruments – as discrete events or ongoing signatures. Seismic methods have been developed, adopted and advanced to study those dynamics at or near the surface of the earth, with unprecedented detail, completeness and resolution. The community of geophysicists interested in earth surface dynamics and geomorphologists, glaciologists, hydrologists, volcanologists, geochemists, biologists and engineering geologists interested in using arising geophysical tools and techniques is progressively growing and collaboratively advancing that emerging scientific discipline.

When you are interested in contributing to or getting to know about the latest methodological and theoretical developments, field and lab scale experimental outcomes, and the broad range of applications in geomorphology, glaciology, hydrology, meteorology, engineering geology, volcanology and natural hazards, then this session would be your choice. We anticipate a lively discussion about standing questions in earth surface dynamics research and how seismic methods could help solving them, we will debate about community based research opportunities and are looking forward to bringing together transdisciplinary knowledge and mutual curiousity.

Topical keywords: erosion, transient, landslide, rockfall, debris flow, fracturing, stress, granular flow, rock mechanics, snow avalanche, calving, icequake, basal motion, subglacial, karst, bedload, flood, GLOF, early warning, coast, tsunami, eruption, tremor, turbidity current, groundwater, soil moisture, noise, dv/v, HVSR, fundamental frequency, polarisation, array, DAS, infra sound, machine learning, classification, experiment.

We are happy to announce Agnes Helmstetter as invited speaker!

Inverse Problems are encountered in many fields of geosciences. One class of inverse problems, in the context of predictability, is assimilation of observations in dynamical models of the system under study. Furthermore, objective quantification of the uncertainty during data assimilation, prediction and validation is the object of growing concern and interest.
This session will be devoted to the presentation and discussion of methods for inverse problems, data assimilation and associated uncertainty quantification throughout the Earth System like in ocean and atmosphere dynamics, atmospheric chemistry, hydrology, climate science, solid earth geophysics and, more generally, in all fields of geosciences.
We encourage presentations on advanced methods, and related mathematical developments, suitable for situations in which local linear and Gaussian hypotheses are not valid and/or for situations in which significant model or observation errors are present. Specific problems arise in situations where coupling is present between different components of the Earth system, which gives rise to the so called coupled data assimilation.
Of interest are also contributions on weakly and strongly coupled data assimilation - methodology and applications, including Numerical Prediction, Environmental forecasts, Earth system monitoring, reanalysis, etc., as well as coupled covariances and the added value of observations at the interfaces of coupled models.
We also welcome contributions dealing with algorithmic aspects and numerical implementation of the solution of inverse problems and quantification of the associated uncertainty, as well as novel methodologies at the crossroad between data assimilation and purely data-driven, machine-learning-type algorithms.

This session is intended to attract a broad range of ice-sheet and glacier modelling contributions, welcoming applied and theoretical contributions. Theoretical topics that are encouraged are higher-order mechanical models, data inversion and assimilation, representation of other earth sub-systems in ice-sheet models, and the incorporation of basal processes and novel constitutive relationships in these models.
Applications of newer modelling themes to ice-sheets and glaciers past and present are particularly encouraged, in particular those considering ice streams, rapid change, grounding line motion and ice-sheet model intercomparisons.

Ice sheets play an active role in the climate system by amplifying, pacing, and potentially driving global climate change over a wide range of time scales. The impact of interactions between ice sheets and climate include changes in atmospheric and ocean temperatures and circulation, global biogeochemical cycles, the global hydrological cycle, vegetation, sea level, and land-surface albedo, which in turn cause additional feedbacks in the climate system. This session will present data and modelling results that examine ice sheet interactions with other components of the climate system over several time scales. Among other topics, issues to be addressed in this session include ice sheet-climate interactions from glacial-interglacial to millennial and centennial time scales, the role of ice sheets in Cenozoic global cooling and the mid-Pleistocene transition, reconstructions of past ice sheets and sea level, the current and future evolution of the ice sheets, and the role of ice sheets in abrupt climate change.

Dynamic subglacial and supraglacial water networks play a key role in the flow and stability of glaciers and ice sheets. The accumulation of meltwater on the surface of ice shelves has been hypothesized as a potential mechanism controlling ice-shelf stability, with ice-shelf collapse triggering substantial increases in discharge of grounded ice. Observations and modelling also suggest that complex hydrological networks occur at the base of glaciers and ice sheets and these systems play a prominent role in controlling the flow of grounded ice. This session tackles the urgent need to better understand the fundamental processes involved in glacial hydrology that need to be addressed in order to accurately predict future ice-sheet evolution and mass loss, and ultimately the contribution to sea-level rise.

We seek contributions from both the modelling and observational communities relating to any area of ice-sheet hydrology. This includes but is not limited to: surface hydrology, melt lake and river formation; meltwater processes within the ice and firn; basal hydrology; subglacial lakes; impacts of meltwater on ice-sheet stability and flow; incorporation of any of these processes into large-scale climate and ice-sheet models.

Ice shelves and tidewater glaciers are sensitive elements of the climate system. Sandwiched between atmosphere and ocean, they are vulnerable to changes in either. The recent disintegration of ice shelves such as Larsen B and Wilkins on the Antarctic Peninsula, current thinning of the ice shelves in the Amundsen Sea sector of West Antarctica, and the recent accelerations of many of Greenland's tidewater glaciers provide evidence of the rapidity with which those systems can respond. Changes in marine-terminating outlets appear to be intimately linked with acceleration and thinning of the ice sheets inland of the grounding line, with immediate consequences for global sea level. Studies of the dynamics and structure of the ice sheets' marine termini and their interactions with atmosphere and ocean are the key to improving our understanding of their response to climate forcing and of their buttressing role for ice streams. The main themes of this session are the dynamics of ice shelves and tidewater glaciers and their interaction with the ocean, atmosphere and the inland ice, including grounding line dynamics. The session includes studies on related processes such as calving, ice fracture, rifting and mass balance, as well as theoretical descriptions of mechanical and thermodynamic processes. We seek contributions both from numerical modelling of ice shelves and tidewater glaciers, including their oceanic and atmospheric environments, and from observational studies of those systems, including glaciological and oceanographic field measurements, as well as remote sensing and laboratory studies.

Recent years have seen significant reductions in Arctic sea ice extent, and sudden ice loss events and redistribution of sea ice in the Antarctic. Climate projections suggest a reduction of the sea ice cover in both poles, with the Arctic becoming seasonally ice free in the latter half of this century.

The scientific community is investing considerable effort in organising our current knowledge of the physical and biogeochemical properties of sea ice, exploring poorly understood sea ice processes, and forecasting future changes of the sea ice cover, such as in CMIP6.

In this session, we invite contributions regarding all aspects of sea ice science and sea ice-climate interactions, including snow and sea ice thermodynamics and dynamics, sea ice-atmosphere and sea ice-ocean interactions, sea ice biological and chemical processes, sea ice observational and field studies and models. A focus on emerging processes and implications is particularly welcome.

The rapid decline of the Arctic sea ice in the last decade is a dramatic indicator of climate change. The Arctic sea ice cover is now thinner, weaker and drifts faster. Freak heatwaves are common. On land, the permafrost is dramatically thawing, glaciers are disappearing, and forest fires are raging. The ocean is also changing: the volume of freshwater stored in the Arctic has increased as have the inputs of coastal runoff from Siberia and Greenland and the exchanges with the Atlantic and Pacific Oceans. As the global surface temperature rises, the Arctic Ocean is speculated to become seasonally ice-free by the mid 21st century, which prompts us to revisit our perceptions of the Arctic system as a whole. What could the Arctic Ocean look like in the future? How are the present changes in the Arctic going to affect and be affected by the lower latitudes? What aspects of the changing Arctic should observational, remote sensing and modelling programmes address in priority?
In this session, we invite contributions from a variety of studies on the recent past, present and future Arctic. We encourage submissions examining interactions between the ocean, atmosphere and sea ice, on emerging mechanisms and feedbacks in the Arctic and on how the Arctic influences the global ocean. Submissions taking a cross-disciplinary, system approach and focussing on emerging cryospheric, oceanic and biogeochemical processes and their links with land are particularly welcome.
The session supports the actions of the United Nations Decade of Ocean Science for Sustainable Development (2021-2030) towards addressing challenges for sustainable development in the Arctic and its diverse regions. We aim to promote discussions on the future plans for Arctic Ocean modelling and measurement strategies, and encourages submissions on the results from IPCC CMIP and the recent observational programs, such as the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), which cosponsors this session.

The interaction between the ocean and the cryosphere in the Southern Ocean has become a major focus in climate research. Antarctic climate change has captured public attention, which has spawned a number of research questions, such as: Is Antarctic sea ice becoming more vulnerable in a changing climate? Where and when will ocean-driven melting of ice shelves yield a tipping point in the Antarctic climate? How does the Antarctic Slope Current interact with the continental shelf and connect the basins around the continent? What role do ice-related processes play in nutrient upwelling on the continental shelf and in triggering carbon export to deep waters? Recent advances in observational technology, data coverage, and modeling provide scientists with a better understanding of the mechanisms involving ice-ocean interactions in the far South. Processes on the Antarctic continental shelf have been identified as missing links between the cryosphere, the global atmosphere and the deep open ocean that need to be captured in large-scale and global model simulations.

This session calls for studies on physical and biogeochemical oceanography and interactions between ice shelves, sea ice and the ocean. This includes work on all scales, from local to basin-scale to circumpolar; as well as paleo, present-day and future applications. Studies based on in-situ observations, remote sensing and regional to global models are welcome. We particularly invite cross-disciplinary topics involving glaciology and biological oceanography as well as contributions from the PALMOD project and the SCAR INSTANT program.

This session is merged from 'Remote Sensing of Permafrost Landscapes' and 'Cold Climate Lake Remote Sensing'

Recent studies show widespread warming of permafrost while simultaneously reports indicate that the Arctic has warmed nearly four times faster than the global average. Increasing temperatures initiate a wide range of landscape and environmental changes, including vegetation changes, changing hydrological and fire regimes as well as abrupt and gradual permafrost thaw features.
This session is intended as a forum for current research on remote sensing of permafrost-dominated landscapes. It addresses (1) recent and upcoming advances of remote sensing of permafrost-related phenomena and permafrost dominated landscapes; (2) the impact of permafrost changes on the natural and human environment; (3) advances and new developments in approaches and analysis techniques. It will bring together investigations of high-latitude and mountain permafrost regions.

We seek contributions that reflect diverse scientific fields, approaches, geographic locations, and data sources (such as satellite, airborne, UAV remote sensing). We particularly encourage contributions that (a) present novel approaches for analysis; (b) outline new strategies to improve process understanding; (c) address different spatial and temporal assessment scales; (d) integrate remote sensing data into earth system models; (e) discuss multi-platform data merging or integration of ground validation data, as well as cloud computing and processing of large data sets. We also encourage contributions focusing on historic satellite data and upcoming satellite missions.

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Lakes in cold regions of the Earth are sensitive to climate change and global warming. Declining lake ice duration, shifting ice timing, and warming of lake water, as shown by recent studies, can alter the hydrological, ecological, and climatological functions of these water bodies, having far-reaching influence beyond their regional context. The scientific study of these cold region lakes and their related observables is of great importance in various fields such as climatology, hydrology, geomorphology, and ecology. Remote sensing together with state-of-the-art data analysis techniques is a powerful tool for scientific observation and analysis of these cold region lakes.

In this session, we invite abstracts that focus on remote sensing of cold climate lake observables such as ice cover, ice thickness, water extent, water level, surface water temperature, and water colour (e.g. turbidity, chlorophyll-a and coloured dissolved organic matter). We encourage studies using either single or multi-source remote sensing platforms, with input data sources including (but not limited to) ground-based webcams, UAVs, and satellite-based optical, thermal and microwave sensors. Both data-driven (e.g., machine learning/deep learning) and physics-inspired approaches will be considered. We especially encourage contributions that aim at large-scale (both spatial and temporal) analysis and/or multi-sensor data fusion. The session offers the opportunity to present results from ongoing research projects.

Present-day glacial and periglacial processes in cold regions, i.e. arctic and alpine environments, provide modern analogues to processes and climatic changes that took place during the Pleistocene, including gradual retreat or collapse of ice sheets and mountain glaciers, and thawing and shrinking of low-land permafrost. Current geomorphological and glaciological changes in mid-latitude mountain ranges could also serve as a proxy for future changes in high-latitude regions within a context of climate change. Examples are speed-up or disintegration of creeping permafrost features or the relictification of rock glaciers.

For our session we invite contributions that either:
1. investigate present-day glacial and/or periglacial landforms, sediments and processes to describe the current state, to reconstruct past environmental conditions and to predict future scenarios in cold regions; or
2. have a Quaternary focus and aim at enhancing our understanding of past glacial, periglacial and paraglacial processes, also through the application of dating techniques.

Case studies that use a multi-disciplinary approach (e.g. field, laboratory and modelling techniques) and/or that highlight the interaction between the glacial, periglacial and paraglacial cryospheric components in cold regions are particularly welcome.

The global cryosphere with all its components is strongly impacted by climate change and has been undergoing significant changes over the past decades. Glaciers are shrinking and thinning. Snow cover and duration is reduced, and permafrost, in both Arctic and mountain environments, is thawing. Changes in sea ice cover and characteristics have attracted widespread attention, and changes in ice sheets are monitored with care and concern. Risks associated with one or several of these cryosphere components have been present throughout history. However, with ongoing climate change, we expect changes in the magnitude and frequency of hazards with profound implications for risks, especially when these interact with other aspects relating to context vulnerability, exposure, and other processes of biophysical and/or socioeconomic drivers of change. New or growing glacier lakes pose a threat to downstream communities through the potential for sudden drainage. Thawing permafrost can destabilize mountain slopes, and eventually result in large landslide or destructive rock and ice avalanches. An accelerated rate of permafrost degradation in low-land areas poses risk to existing and planned infrastructure and raises concerns about large-scale emission of greenhouse gases currently trapped in Arctic permafrost. Decreased summertime sea ice extent may produce both risks and opportunities in terms of large-scale climate feedbacks and alterations, coastal vulnerability, and new access to transport routes and natural resources. Furthermore, rapid acceleration of outlet glacier ice discharge and collapse of ice sheets is of major concern for sea level change. This session invites contributions across all cryosphere components that address risks associated with observed or projected physical processes. Contributions considering more than one cryosphere component (e.g. glaciers and permafrost) are particularly encouraged, as well as contributions on cascading processes and interconnected risks. Contributions can consider hazards and risks related to changes in the past, present or future. Furthermore, Contributions may consider one or several components of risks (i.e. natural hazards, exposure, vulnerability) as long as conceptual clarity is ensured. Furthermore, cases that explore diverse experiences with inter- and transdisciplinary research, that sought to address these risks with communities through adaptation and resilience building, are also be considered.

Snow cover characteristics (e.g. spatial distribution, surface and internal physical properties) are continuously evolving over a wide range of scales due to meteorological conditions, such as precipitation, wind and radiation.
Most processes occurring in the snow cover depend on the vertical and horizontal distribution of its physical properties, which are primarily controlled by the microstructure of snow (e.g. density, specific surface area). In turn, snow metamorphism changes the microstructure, leading to feedback loops that affect the snow cover on coarser scales. This can have far-reaching implications for a wide range of applications, including snow hydrology, weather forecasting, climate modelling, and avalanche hazard forecasting or remote sensing of snow. The characterization of snow thus demands synergetic investigations of the hierarchy of processes across the scales ranging from explicit microstructure-based studies to sub-grid parameterizations for unresolved processes in large-scale phenomena (e.g. albedo, drifting snow).

This session is therefore devoted to modelling and measuring snow processes across scales. The aim is to gather researchers from various disciplines to share their expertise on snow processes in seasonal and perennial snowpacks. We invite contributions ranging from “small” scales, as encountered in microstructure studies, over “intermediate” scales typically relevant for 1D snowpack models, up to “coarse” scales, that typically emerge for spatially distributed modelling over mountainous or polar snow- and ice-covered regions. Specifically, we welcome contributions reporting results from field, laboratory and numerical studies of the physical and chemical evolution of snowpacks, statistical or dynamic downscaling methods of atmospheric driving data, assimilation of in-situ and remotely sensed observations, representation of sub-grid processes in coarse-scale models, and evaluation of model performance and associated uncertainties.

Snow avalanches range among the most prominent natural hazards which threaten mountain communities worldwide, in particular also in the context of climate change. Snow avalanche formation involves complex interacting processes starting with failure processes at the scale of snow crystals and ending with the release of a large volume of snow at a scale of up to several hundred meters. The practical application of avalanche formation is avalanche forecasting, requiring a thorough understanding of the physical and mechanical properties of snow as well as the influence of meteorological boundary conditions (e.g. precipitation, wind and radiation).

This session aims to improve our understanding of avalanche formation processes and to foster the application to avalanche forecasting. We welcome contributions from novel field, laboratory and numerical studies as well as specific case studies. Topics include, but are not limited to, snow micro-mechanics, snow cover simulations, meteorological driving factors including drifting and blowing snow, spatial variability, avalanche release mechanics, remote avalanche detection, avalanche forecasting and the impact of climate change. While the main focus of this session is on avalanche formation, detection and forecasting, it is closely linked to the session ‘Snow avalanche dynamics: from driving processes to mitigation strategies’, which addresses avalanche dynamics, risk assessment and mitigation strategies.

Water stored in the snow pack and in glaciers represents an important component of the hydrological budget in many regions of the world, as well as a sustainment to life during dry seasons. Predicted impacts of climate change in catchments covered by snow or glaciers (including a shift from snow to rain, earlier snowmelt, and a decrease in peak snow accumulation) will reflect both on water resources availability and water uses at multiple scales, with potential implications for energy and food production.

The generation of runoff in catchments that are impacted by snow or ice, profoundly differs from rainfed catchments. And yet, our knowledge of snow/ice accumulation and melt patterns and their impact on runoff is highly uncertain, because of both limited availability and inherently large spatial variability of hydrological and weather data in such areas. This translates into limited process understanding, especially in a warming climate.

This session aims at bringing together those scientists that define themselves to some extent as cold region hydrologists, as large as this field can be. Contributions addressing the following topics are welcome:
- Experimental research on snow-melt & ice-melt runoff processes and potential implementation in hydrological models;
- Development of novel strategies for snowmelt runoff modelling in various (or changing) climatic and land-cover conditions;
- Evaluation of remote-sensing or in-situ snow products and application for snowmelt runoff calibration, data assimilation, streamflow forecasting or snow and ice physical properties quantification;
- Observational and modelling studies that shed new light on hydrological processes in glacier-covered catchments, e.g. impacts of glacier retreat on water resources and water storage dynamics or the application of techniques for tracing water flow paths;
- Studies on cryosphere-influenced mountain hydrology, such as landforms at high elevations and their relationship with streamflow, water balance of snow/ice-dominated mountain regions;
- Studies addressing the impact of climate change on the water cycle of snow and ice affected catchments.

The cryosphere and polar regions have changed dramatically in recent years. Perhaps nowhere has this been more clear than in sea ice, which has seen significant decline; however, there remain challenges in developing models to understand and project further changes. Such ongoing changes in the polar regions and cryosphere have been linked to climate change but formal attribution studies have only just begun to emerge. Our new session focuses on these two aspects: sea ice modelling and the nascent field of polar & cryosphere attribution.

The first part of the session will focus on attribution studies – which involves making quantitative statements about likely causes of climate change and how climate change affects the likelihood of individual weather events – of the polar regions and cryosphere. Contributions are from a variety of aspects under the entire cryospheric and polar attribution umbrella: ranging across time scales from individual events to long term change, and from historical and paleo studies to future changes; from local to global; from ice sheets to river ice; from anthropogenically induced to focussed on a specific forcing or range of different forcings; and from methods to applications.

In the second part of the session, we will discuss new model approaches and mathematical techniques to simulate sea ice. Sea ice is governed by a variety of small-scale processes that affect the large-scale dynamics of the system. Recently, a number of new approaches have been developed including new rheologies, discrete element models and machine learning techniques to model and parametrize nonlinear relationships governing sea-ice behaviour.

The polar climate system is strongly affected by interactions between the atmosphere and the cryosphere. Processes that exchange heat, moisture and momentum between land ice, sea ice and the atmosphere, such as katabatic winds, blowing snow, ice melt, polynya formation and sea ice transport, play an important role in local-to-global processes. Atmosphere-ice interactions are also triggered by synoptic weather phenomena such as cold air outbreaks, polar lows, atmospheric rivers, Foehn winds and heatwaves. However, our understanding of these processes is still incomplete. Despite being a crucial milestone for reaching accurate projections of future climate change in Polar Regions, deciphering the interplay between the atmosphere, land ice and sea ice on different spatial and temporal scales, remains a major challenge.

This session aims at showcasing recent research progress and augmenting existing knowledge in polar meteorology and climate and the atmosphere-land ice-sea ice coupling in both the Northern and Southern Hemispheres. It will provide a setting to foster discussion and help identify gaps, tools, and studies that can be designed to address these open questions. It is also the opportunity to convey newly acquired knowledge to the community.

We invite contributions on all observational and numerical modelling aspects of Arctic and Antarctic meteorology and climatology, that address atmospheric interactions with the cryosphere. This may include but is not limited to studies on past, present and future of:
- Atmospheric processes that influence sea-ice (snow on sea ice, sea ice melt, polynya formation and sea ice production and transport) and associated feedbacks,
- The variability of the polar large-scale atmospheric circulation (such as polar jets, the circumpolar trough and storm tracks) and impact on the cryosphere (sea ice and land ice),
- Atmosphere-ice interactions triggered by synoptic and meso-scale weather phenomena such as cold air outbreaks, katabatic winds, extratropical cyclones, polar cyclones, atmospheric rivers, Foehn winds and heatwaves,
- Role of clouds in polar climate and impact on the land ice and sea ice through interactions with radiation,
- Teleconnections and climate indices and their role in land ice/sea ice variability.

The interactions between the atmosphere, ocean and sea ice play an important role in shaping the polar climates. However, existing knowledge of the physical, chemical, and biogeochemical processes that underly the exchanges of mass, energy and momentum between these components remain poorly understood.

Closing knowledge gaps on the interactions between the atmosphere, ocean and sea-ice can considerably advance our ability to understand recent changes, and anticipate future changes in the Arctic and Antarctic climate systems. In particular, closing these knowledge gaps will improve our ability to represent them in our modelling systems and increase confidence in projections of future climate change in the polar regions.

This session will highlight 1) recent advances in our knowledge of atmosphere-ocean-sea ice interactions and 2) new and emerging tools and datasets that can close these knowledge gaps.

We welcome observational and numerical modelling studies of physical and chemical atmospheric and ocean processes that underly interactions in the coupled climate system in both the Arctic and Antarctic. This includes but is not limited to:

Cloud microphysics and aerosol-cloud interactions, and their role in the coupled system;
Atmospheric Boundary Layer (ABL) dynamics and its interactions with the sea-ice surface;
Sea ice dynamics and thermodynamics, e.g. wind driven sea-ice drift, snow on ice;
Upper ocean mixing processes;
Sea ice biogeochemistry and interactions at interfaces with sea ice;
Snow on sea ice and it’s role in the coupled ocean-ice-atmosphere system;
Surface energy budget of the coupled system, including contributions of ABL-dependent turbulent fluxes, clouds and radiative fluxes, precipitation and factors controlling snow/sea ice albedo.
Presentations showcasing recent or emerging tools, observational campaigns, or remote sensing datasets are encouraged.

Atmosphere and Cryosphere are closely linked and need to be investigated as an interdisciplinary subject. Most of the cryospheric areas have undergone severe changes in last decades while such areas have been more fragile and less adaptable to global climate changes. This AS-CR session invites model- and observational-based investigations on any aspects of linkages between atmospheric processes and snow and ice on local, regional and global scales. Emphasis is given on the Arctic and Antarctic regions, high latitudes and altitudes, mountains, sea ice and permafrost regions. In particular, we encourage studies that address aerosols (such as Black Carbon, Organic Carbon, dust, volcanic ash, microplastics, pollen, sea salt, diatoms, bioaerosols, bacteria, etc.) and changes in the cryosphere, e.g., effects on snow/ice melt and albedo. The session also focuses on dust transport, aeolian deposition, and volcanic dust, including health, environmental or climate impacts at high latitudes, high altitudes and cold Polar Regions. We include contributions on biological and ecological sciences including dust-organisms interactions, cryoconites, bio-albedo, eco-physiological, biogeochemical and genomic studies. Related topics are light absorbing impurities, cold deserts, dust storms, long-range transport, glaciers darkening, polar ecology, and more. The scientific understanding of the AS-CR interaction needs to be addressed better and linked to the global climate predictions scenarios.

In 2015, the UN Sustainable Development Goals and the Paris Agreement on climate recognized the deteriorating resilience of the Earth system, with planetary-scale human impacts constituting a new geological epoch: the Anthropocene. Earth system resilience critically depends on the nonlinear interplay of positive and negative feedbacks of biophysical and increasingly also socio-economic processes. These include dynamics and interactions between the carbon cycle, the atmosphere, oceans, large-scale ecosystems, and the cryosphere, as well as the dynamics and perturbations associated with human activities.

With rising anthropogenic pressures, there is an increasing risk we might be hitting the ceiling of some of the self-regulating feedbacks of the Earth System, and cross tipping points which could trigger large-scale and partly irreversible impacts on the environment, and impact the livelihood of millions of people. Potential domino effects or tipping cascades could arise due to the interactions between these tipping elements and lead to a further decline of Earth resilience. At the same time, there is growing evidence supporting the potential of positive (social) tipping points that could propel rapid decarbonization and transformative change towards global sustainability.

In this session we invite contributions on all topics relating to tipping points in the Earth system, positive (social) tipping, as well as their interaction and domino effects. We are particularly interested in various methodological approaches, from Earth system modelling to conceptual modelling and data analysis of nonlinearities, tipping points and abrupt shifts in the Earth system.