Division V: Cryosphere, Atmosphere, and Climate

Division Head: Anais Orsi

Within the climate system, frozen water is present in different forms (snow, sea ice, lake and river ice, glaciers, ice sheets, icebergs and frozen ground) altogether defined as the cryosphere. The state of the cryosphere strongly depends on and interacts with atmospheric conditions, on local to hemispheric spatial scales, and on hourly to glacial-interglacial scales. The cryosphere has a non linear response to changes in temperature, due to threshold effects associated with melt. Many interactions take place between the cryosphere and the climate system. For instance, land ice meltwater fluxes affect ocean salinity, density and circulation, and, vice versa, ocean circulation affects subsurface melting of ice shelves. The cryosphere also strongy impacts surface energy, greenhouse gases and water fluxes. Changes in Arctic sea ice and snow cover may affect the mid-latitude atmospheric circulation. Changes in albedo associated with reduced snow and ice cover result in positive feedbacks amplifying climate change. Together with ocean thermal expansion, melting and calving from glaciers and ice sheets drive changes in the global mean sea level on timescales up to thousands of years. The cryosphere is therefore a key component of the global climate system. Past and and present changes in the state of the cryosphere provide sensitive indicators of climatic changes. Ice cores offer comprehensive records of past changes in polar climate and water cycle, aerosol deposition, natural forcings (including solar and volcanic activity), and global atmospheric composition. Paleoclimate reconstructions and simulations allows to learn from past « natural experiments » on the climate system, and to identify the response and role of the cryosphere. They also provide benchmark information to test the realism of Earth system models. Observations and modelling are needed to understand the cryosphere – atmosphere – climate interactions. Present-day monitoring is critical for process-based understanding and regional climate-cryosphere model assessment and development. Methodological developments are needed for the comparison between model results and observations, for the coupling between e.g. climate and ice sheet models, and for assessing regional impacts of climate change in cold regions.

The Division Cryosphere, Atmosphere, and Climate aims at promoting collaborative work and discussion among cryosphere, atmosphere and climate scientists, stimulate model-data comparisons and exchange of information throughout different space time scales. It works in collaboration with the Scientific Committee on Antarctic Research (SCAR), Climate of the Cryosphere (WRCP/CLIC), the Paleoclimate Modelling Intercomparison Project (PMIP), with the IUGG Commission on Climate and Environmental Change (CCEC), the IAMAS International Commission on Climate (ICCL), and with the International Partnerships in Ice Core Drilling (IPICS).