In this research section an improved understanding of polar climate changes will be reached through measurements and modelling.
Polar regions are key players in the climate system because of the strong modification of the surface energy budget through snow and ice cover, which is tightly coupled to the global circulation of the atmosphere and the ocean. The climate of the Arctic is subject to visible changes and the sea-ice albedo feedback mechanism acts as an amplifier of climate change. The observed decrease of Arctic summer sea ice cover over the last decades is best viewed as a combination of strong natural variability due to large-scale dynamics and regional feedbacks in the coupled ice-ocean-atmosphere system and a growing radiative forcing associated with rising concentrations of atmospheric greenhouse gases. The attribution of ongoing changes in the Arctic and Antarctic is difficult because natural variability is large, masking the evidence of anthropogenic influences.
Atmospheric measurements of surface energy balance, heat and moisture fluxes, cloud and aerosol properties, water vapour and ozone are essential for the understanding of key processes in the Arctic and Antarctic climate system. Major gaps and uncertainties exist in the knowledge of processes governing e .g. the build-up of aerosols in the Arctic and its role for climate change. Processes in polar regions, connected with a variety of feedbacks, including cloud-, aerosol-, ozone-, planetary boundary layer-, and sea ice processes introduce implications on the global scale and are not well represented in climate models. Therefore improvements of a variety of sub-grid scale process parameterizations including sea ice- and soil processes, surface fluxes, albedo, clouds and aerosols are needed. Changes in the polar energy sink region exert a strong influence on the mid- and high-latitude climate by modulating the strength of the sub-polar westerlies, the atmospheric teleconnection patterns and storm tracks. Disturbances in the wintertime Arctic sea-ice and snow cover induce perturbations in planetary wave train and atmospheric teleconnection patterns and impacts on the strength of European winters.
We focus on coupled atmosphere-sea ice-ocean feedbacks, atmosphere-surface-frozen soil interactions, linkages between boundary layer and baroclinic cyclones, aerosol- and cloud feedbacks and stratospheric ozone layer-climate interactions.