Work package POL 3: Variations of the Arctic physical environment
Our aim is to investigate the origin and structure of the variability of the Arctic Ocean
circulation and its heat and fresh water fluxes in present and past climate states. In the
recent past significant changes were observed in the Arctic: A warmer atmosphere was
associated with thawing of Siberian permafrost and glaciers, increase of precipitation and of
river discharge, and at the same time warming of intermediate water, decrease of the ice
cover, changes in the ocean circulation patterns and weakening of the stability of the water
column (“retreat of the halocline”) occurred. These changes are closely linked to the
variability of hemispheric atmospheric patterns like the NAO or the AO. All these changes
impose substantial consequences for the biological system and for the climate on a global
scale. According to model results, the Arctic fresh water balance has a strong influence on
the meridional overturning circulation in the Atlantic. River runoff/ocean/ice changes are
also expected to have a strong feedback to the atmosphere through changes in the heat
exchange between ocean and atmosphere. The recent variations have been qualitatively
reproduced by atmospherically driven ice/ocean GCMs. Yet it is unclear whether the Arctic
environment is shifting into a state different from the past decades or if we observe a phase
of an oscillatory pattern.