C01 Advances in Modelling Glaciers and Ice Caps – Past Reconstructions, Future Projections, and Process-Based Studies

Convener(s): Daniel Farinotti (Switzerland)

Co-Convener(s): Yongmei Gong (Norway) Mathieu Morlighem (USA) Harry Zekollari (Switzerland)

"Mountain glaciers and ice caps are important freshwater resources, contribute significantly to present-day sea level rise, and can be a significant source of hazard. Numerical models of glaciers and ice caps are needed to understand past changes, to project future evolutions, and to quantify associated impacts. This symposium focuses on all aspects of modelling glaciers and ice caps other than the ice sheets, including but not limited to the following topics:
- Coupling of glacier mass balance models with ice flow models;
- Integration of physical processes, such as subglacial drainage or glacier calving, into existing models;
- Inverse modelling of subsurface characteristics;
- Inference of glacier ice thickness from surface measurements.
Studies on all spatial and temporal scales, including past reconstructions and future projections are solicited, with particular emphasis on regional-scale studies and high-mountain environments. "

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C02 Glacier Changes in High Mountain Asia and the Karakoram Anomaly: Latest Insights From the Atmosphere and Cryosphere

Convener(s): Frank Paul (Switzerland)

Co-Convener(s): Emily Collier (Austria) Daniel Farinotti (Switzerland) Pankaj Kumar (India)

Snow cover and glacier changes in High Mountain Asia (HMA) have been intensely studied over the past two decades, mostly using satellite data, numerical models, and an increasing number of field observations. The interest in the region is high, as snow and glacier melt are of high importance for the water resources of millions of people living downstream of major mountain ranges. Of similar interest are the still poorly understood reasons for the high spatial variability of cryospheric changes, and amongst these, the so-called ‘Karakoram Anomaly’ is of particular interest. Marking a region with stable or advancing (and often surging) glaciers, balanced mass budgets, and decreasing (summer) temperatures, the glacier evolution in the Karakoram is in stark contrast to the strong retreat and mass loss observed elsewhere in HMA and most other glacierized regions on earth. With limited availability of temperature and precipitation observations, an extremely steep and high topography, a strong influence of the monsoon and westerly climate regimes, and nearly absent glacier mass balance measurements, our understanding of the governing processes are still vague. The combination of atmospheric and glaciological modelling with remote sensing observations has a great potential to improve our knowledge, and further progress is required if the future of the cryosphere and the water cycle are to be predicted correctly. For this symposium, we invite contributions reporting on the latest findings on cryospheric and atmospheric changes in HMA. We invite contributions based on remote sensing observations, field surveys or numerical modelling. We envision a special focus on the Karakoram Anomaly, but invite contributions from nearby regions as well. We particularly welcome studies that synergistically combine atmospheric and cryospheric modelling with remote sensing data or studies that investigate possible drivers of observed changes.

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C03 Debris Covered Glaciers

Convener(s): Francesca Pellicciotti (Switzerland)

Co-Convener(s): David Rounce (USA) Mike McCarthy (Switzerland) Lindsey Nicholson (Austria)

Rock debris accumulating on glacier surfaces alters glacier energy balance, melt, mass balance and ice dynamics. The structure of debris cover is unique to each glacier and sensitive to climate, and an ever-growing body of research has embraced this complexity by looking at debris and its effects across scales. Research on debris-ice interactions spans point scale observations and simulations to mapping efforts at regional and global scales. While we are increasingly able to model ice melt under a static debris layer, and the knock-on effects of this for mass balance and ice dynamics, simulating the transit of debris through a glacier from its supply slopes is a major challenge, and debris remobilisation on the glacier surface remains elusive. The role of debris in the hydrology of single glaciers and entire catchments remains little understood. Despite advances in our understanding of surface processes, mass balance, hydrology, dynamics and long-term evolution of debris-covered glaciers, many open questions remain. This session aims to bring together results from numerical modelling, field observations and remote sensing to understand debris-ice interactions across scales. We invite contributions that include: i) the formation, characteristics and movement of supraglacial debris, including debris supply (e.g. headwall and subglacial erosion, avalanching), transport (englacial and supraglacial) and export; ii) studies of debris-covered glacier energy and mass balance, including at surface features such as supraglacial ponds and ice cliffs; iii) the hydrology of debris-covered glaciers and debris’ role in altering catchment hydrographs at annual to decadal scales; iv) debris-covered glacier dynamics; v) remote-sensing observations and numerical modelling of debris-covered glaciers and prediction of their changes in response to future climate forcing; vi) long term evolution of debris-covered glaciers and reconstructions of former glaciers; and vii) hazards associated with debris-covered glaciers such as glacial lake outburst floods and debris flows.

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C04 Fast Glacier Flow: Processes, Observations and Modelling of Ice Streams, Tidewater Glaciers and Surging Glaciers

Convener(s): Christine Hvidberg (Denmark)

Co-Convener(s): Ralf Greve (Japan) Ronja Reese (UK)

Fast flowing ice streams and glaciers are important in maintaining the overall mass balance of the Greenland and Antarctic ice sheets, yet the conditions that facilitate and regulate their fast flow remain poorly understood. The mechanics that govern fast flow and surging appear to be very responsive to changing conditions in the subglacial environment and at the front with effects on the whole glacier system. This symposium welcomes contributions from studies of ice streams, tidewater glaciers and surging glaciers, including the subglacial hydrology, shear margin processes, grounding line dynamics, the buttressing role of ice shelves and floating tongues, calving, the influence of surface meltwater and lake drainage, and other ice deformation and mechanical studies related to fast flow. Process studies, observations and/or numerical modelling investigations are all welcome.

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C05 Tropical Glaciers: Mass Changes, Climate Forcing and Impacts on Indigenous Communities

Convener(s): Nicolas Cullen (New Zealand)

Co-Convener(s): Jean Emmanuel Sicart (France) Thomas Mölg (Germany) Rainer Prinz (Austria) Marion Réveillet (France)

"The recent changes to tropical glaciers have been dramatic and, given their importance to ecosystems, agriculture, freshwater, energy production and local communities, it remains critical that we continue to assess their sensitivity to climate change. This symposium will focus on the latest efforts and techniques to detect recent changes to tropical glaciers using observations, atmospheric and glaciological modelling and remote sensing, as well as recognising the importance of local, indigenous knowledge to understand the impact of these changes over different spatial and temporal scales. Topics may include but are not limited to:
- glacier energy and mass balance and their linkages to climate variability and change in the tropics
- the importance of atmospheric and climate dynamics in controlling tropical glaciers
- assessment of changes in the area and hypsometry of tropical glaciers using historical archives and/or integrating field-based observations with remote sensing
- reconstruction of tropical climate from ice cores and other natural archives
- the effects of mass changes on hazards and water resources and related natural and socio-economic systems in the recent past, present and future
- using indigenous knowledge to understand how changes to tropical glaciers are impacting people and the landscape We especially welcome contributions that integrate local, indigenous knowledge with observations, modelling and remote sensing."

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C06 New Frontiers in Paleoclimate Reconstructions and Proxy Interpretations From Ice Cores

Convener(s): Ji-Woong Yang (France)

Co-Convener(s): Mathieu Casado (France) Barbara Stenni (Italy) Christo Buizert (USA)

The last IPCC report highlighted remaining large uncertainties in the future evolution of the cryosphere with direct consequences on global sea level rise. Understanding past climate variability and sensitivity from glacial archives is thus fundamental for placing the current changes in a longer-term context. The scientific ice core community is currently putting an enormous effort towards (1) retrieving the oldest continuous ice core from Antarctica (Project Beyond EPICA) and (2) training a new generation of ice core scientists capable of analysing, interpreting, and modelling the new records that will be obtained (ITN DEEPICE project). In addition, the ice cores retrieved in high-altitude/low-latitude glaciers are offering a wealth of paleoclimate information covering the last centuries and millennia, preserved in what is called the third pole. We invite contributions reporting new results or data/model studies related to ice cores drilled in both polar regions and mid-low latitude glaciers and covering temporal scales spanning from the last decades to glacial-interglacial cycles. Contributions presenting novel techniques for (1) advances in new proxies and increasing temporal resolution, (2) interpreting the paleoclimate records with new statistical techniques, (3) understanding the post-depositional processes potentially affecting the integrity of the records as well as new tools for (4) dating and (5) modelling paleoclimatic signals are welcomed.

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C07 Mass Changes of The Cryosphere – The Need for and Lessons Learned From Intercomparison Exercises

Convener(s): Michael Zemp (Switzerland)

Co-Convener(s): Kari Luojus (Finland) Julienne Stroeve (USA) Annett Bartsch (Austria) Inès Otosaka (UK)

Climate change has strongly impacted the Earth’s cryosphere over the past decades. These changes strongly affect the planetary radiative forcing, global sea level, oceanic conditions, atmospheric circulation, and freshwater resources. Satellite observations have pushed the monitoring of the cryosphere and resulted in numerous global estimates of changes in ice sheets, glaciers, sea ice, snow, and permafrost. However, the latest IPCC assessment reports (IPCC SROCC and AR6) highlighted the shortcomings of the current methods: while an increasing number of estimates are now becoming available from various sources, there are large variations between some of these assessments, beyond stated uncertainties. This call for coordinated intercomparison exercises of mass-change estimates derived from various remote sensing sources for each of the cryospheric components. The present session invites contributions presenting global and regional assessments of mass-change estimates from the different cryospheric components and various sources, discussing lessons learned from existing intercomparison exercises such as the Ice Sheet Mass-Balance Intercomparison Exercise (www.imbie.org) or the Glacier Mass-Balance Intercomparison Exercise (www.glambie.org), and demonstrating the need for similar activities for the other cryosphere components.

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C08 Challenges in Modeling, Monitoring and Predicting Alpine Mass Movements

Convener(s): Johan Gaume (Switzerland)

Co-Convener(s): Jessica Much (Switzerland) Alessandro Cicoira (Switzerland) Julia Kowalski (Germany) Jan-Thomas Fischer (Austria) Alec van Herwijnen (Switzerland)

Climate change is particularly affecting the high-mountain cryosphere, which includes glaciers, permafrost and snow. These changes affect the frequency and intensity of alpine mass movements, requiring updated risk management procedures and resilient mitigation measures. Such adaptation strategies would strongly benefit from a deeper understanding of the underlying mechanical processes at play, improved monitoring capabilities, and suitable and efficient modeling approaches. This session aims to improve our understanding of the crucial processes in the initiation and dynamics of alpine mass movements with the ultimate focus to improve prediction and mitigation measures. We thus welcome novel contributions related to the modeling, monitoring and prediction of alpine mass movements, including glacier and permafrost instabilities, snow/ice/rock avalanches and cascading processes such as glacial lake outburst floods. We propose to foster discussions around topics including (but not limited to) constitutive and rheological models, depth-averaged and particle-based methods, model parameter estimation, event detection and monitoring, data-driven / machine learning approaches, surrogate models and uncertainty quantification. Concerning processes, of particular interest is the role of water in solid and/or liquid states on slope stability and flow rheology/mobility, entrainment of glacier ice or saturated sediments, liquefaction, interaction with obstacles, forests or mitigation structures.

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C09 Mountain Snow Cover Under Climate Change: From Past to Future

Convener(s): Wolfgang Schoener (Austria)

Co-Convener(s): Lijuan Ma (China) Shawn Marshall (Canada)

Climate change has a significant impact on the amount and spatial and temporal distribution of snow cover in mountain regions across the globe. Several studies show that this response of snow cover to climate change in different mountain regions is not a simple effect of temperature change, but depends on several factors, such as geographical location (climate zone), latitude and regional atmospheric influences (e.g. interaction with synoptic-scale atmospheric flows). However, the observational capacities and process understanding of these interactions are very different for the individual mountain regions. Often there are inventories of snow cover changes designated as global (but excluding mountain regions), e.g. based on satellite data (ESA-GCW Snow-Watch, etc.), as well as numerous process studies and selected data for some mountain regions. Despite the great importance of snow in mountain regions, a comprehensive inventory of mountain snow cover on a global scale based on robust data is missing so far. Regional inventories are limited in particular to a few well-monitored mountain regions such as the US Rockies and the European Alps. Overcoming this research gap is a major motivation for the recently established Joint Body "Status of Mountain Snow Cover", as a joint effort of IACS, WMO and MRI. The aim of the session is to bring together the knowledge and experience of researchers from different mountain regions of the world working on climate change-induced changes in snow cover, to present the current state of knowledge and to identify research gaps. Given the overall importance of snow for ecology, the economy and human life in general, researchers from diverse and also interdisciplinary fields are called upon to contribute, and these are encouraged for all mountain regions of the world and using a wide variety of data sources and analytical methods.

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C10 Satellite-Derived Snow Cover Products and Their Applications in Hydrology

Convener(s): Ali Arslan (Finland)

Co-Convener(s): Zuhal Akyurek (Turkey) Carlo de Michele (Italy) Aynur Şensoy Şorman (Turkey) Matias Takala (Finland)

Satellite-derived snow cover products are crucial because they provide aerial/spatial information. The satellite-derived snow cover products are used for flood forecasting in snow dominated basins for short or medium range forecasting periods. These are useful for planning and management of water resources, reservoir control in the sense of floods or droughts, and hydropower generation. Snow storage in terms of aerial coverage and snow water equivalent are highly important in support for decision making. With longer data records, these products also serve for climate change impact analyses in hydrology. In this session, we welcome presentations of all new, improved, and future satellite-derived snow products and their applications in hydrology.

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C11 Light Absorbing Particles on Snow and Ice

Convener(s): Maria Gritsevich (Finland)

Co-Convener(s): Marie Dumont (France) Outi Meinander (Finland) McKenzie Skiles (USA) Biagio Di Mauro (Italy) Pavla Dagsson Waldhauserova (Iceland)

Light absorbing particles such as black carbon, volcanic ashes, mineral dust or algae modify the albedo of snow and ice. Consequently, the amount of solar radiation absorbed by snow or ice is increased, potentially accelerating melt and triggering potent feedbacks. This session invites any contribution related to light absorbing particles on snow and ice, be they related to the impacts of light absorbing particles, the transport or the deposition processes. This includes measurement studies at small or large scales as well as modelling studies.

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C12 Spotlighting Divergence: Climate Change Refugia Within Snow-Dominated Catchments and Where to Find Them

Convener(s): Alfonso Fernández (Chile)

Co-Convener(s): Mario Lillo (Chile) Deigo Rivera (Chile) Marcelo Somos-Valenzuela (Chile) Edilia Jacque (Chile) Ana Huaico (Chile)

Under current rates of climate warming, glaciers and snow continue a rapid shrinkage almost everywhere. Most glacierized mountain areas are already showing the impacts of ice and snow loss on streamflow, hazards, tourism, and hydropower, among others. However, although fluctuations in temperature and precipitation are intrinsically linked to dynamics of mass loss and gain, there are several examples of mountain regions with similar size and elevation range, and located within broadly homogenous climatic regimes, that have shown differential climatic responses in recent decades. These seemingly anomalous climatic sensitivities can be linked to topographic constraints leading to particular hypsometric distributions. Collectively, these conditions may allow glaciers and snow to remain providing ecosystem functions even in the most extreme climatic scenarios. Under these circumstances, some snow-dominated watersheds may constitute climate change refugia in hydrological terms. In this session, we aim to attract studies that are looking at regional to local topoclimatic conditions controlling resistance to climate warming within snow-dominated catchments. Studies involving glacier-climate sensitivity, snow hydrology, debris-cover impact on the surface energy balance, paleoglacier extents, geomorphometry, and streamflow from glacierized environments are welcome. We expect to fuel a discussion on how to pinpoint locations most likely to host refugia under different climatic projections.

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C13 Data Driven Cryospheric Sciences: Machine Learning, Data Assimilation and Inverse Methods for the Cryosphere

Convener(s): Fabien Maussion (Austria)

Co-Convener(s): Jordi Bolibar (Netherlands) Celia Baumhoer (Germany) Hui Tang (Germany) Facu Sapienza (USA)

The recent exponential increase in Earth observations together with important advances in data science and statistics/machine learning are opening the door to new ways of exploring and understanding physical processes and interactions within the cryosphere. These new tools have been used to exploit large remote sensing datasets for image segmentation, causal analysis, inverse methods, physics-informed learning and to design more efficient surrogate models. With the quick rise of all these approaches, there is a need to bring them together in a common space of discussion in order to track what progress has been made so far. With this in mind, in this session we welcome studies which combine novel data-driven efforts to better understand and quantify physical processes within the different subfields of the cryosphere. These include - but are not limited to - (i) computer vision studies focusing on image classification, (ii) inverse and physics-informed learning methods to better constrain and understand physical processes, (iii) pure data-driven methods to explore alternative modelling approaches, and (iv) surrogate models to accelerate simulations as well as new ways of exploring models (e.g. probabilistic methods).

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C14 Cryospheric Processes and Related Socioeconomic Impacts

Convener(s): Cunde Xiao (China)

Co-Convener(s): Wouter Buytaert (UK) Christian Huggel (Switzerland) Xiaoming Wang (Australia)

Cryospheric Processes and Related Socioeconomic Impacts "Significant human populations live within or adjacent to polar and alpine regions. The cryosphere provides water resources that support irrigation, hydropower generation, and other economic benefits such as tourism. This symposium focuses on all aspects of “cryospheric impacts” that include both services (benefits that humanity gains from cryospheric systems) and hazards. We seek submissions including, but not limited to, the following topics:
- Services that are provisioned, regulated or supported by the cryosphere
- Hazards that are originated, connected or amplified by the cryosphere
- Cryospheric processes that influence the above services and hazards
- Changes in the cryosphere including tipping points or thresholds that may result in putting services at risk, and/or cascading hazards
- Methods or assessments of the social and/or economic value of cryospheric services. "

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C15 Progress in Quantifying Ice-Sheet Surface Mass Balance: Past, Present and Future

Convener(s): Cécile Agosta (France)

Co-Convener(s): Miren Vizcaino (Netherlands) Yetang Wang (China)

"We focus on the surface mass balance (SMB) of ice-sheets, including individual mass balance components, feedbacks and associated uncertainties, and advancing process understanding from models (regional and global) and/or observations (ground-based and remote). Topics include but are not limited to
- Quantification of ice-sheet SMB and its uncertainties for paleoclimate and the recent past (1850-present) including melt, runoff, sublimation, refreezing, and snow accumulation.
- Advances in the understanding of key processes relevant for surface mass fluxes, including for example, surface and firn hydrology, drifting snow, and the effect of impurities on melt
- Quantification of feedbacks between ice sheet SMB and components of the climate system at decadal to centennial time scales, including mass balance/elevation feedbacks, linkages to sea surface conditions, and impacts of storm tracks and large-scale circulation patterns.
- Projections of ice sheet SMB for the next decades to the next few centuries and beyond, and associated uncertainties, from regional and global climate models. "

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