The great polar melt

The Arctic sea ice is dwindling at dizzying speed. Researchers of the Alfred Wegener Institute, Bremerhaven, assume that the cause lies in the interplay of ice, ocean and atmosphere. Using models, process studies and long-term observations, they hope to identify the precise mechanisms of this process. They are joining forces with colleagues from 13 countries and 48 partner institutes within the framework of the EU project DAMOCLES (Developing Arctic Modelling and Observing Capabilities for Long-term Environment Studies). To carry out observations independently of expeditions, for example, autonomous buoys deployed on ice flows regularly transmit information about currents, temperature and salinity via satellite. An important quantity of the sea ice budget, the thickness, is studied by the AWI sea ice experts. Besides melting, also wind piling up ice floes decreases the area of sea ice, but does not change the quantity. In the regions studied by DAMOCLES, the ice has become thinner. Since natural climate variation is overlaying the greenhouse effect, the very abrupt sea ice decline in recent years suggests that the northern polar region is particularly sensitive due to a positive feedback: When the white ice cover decreases more dark sea surface can absorb sunlight, which speeds up the melting. “Also the temperature of the Arctic Ocean has increased markedly to a depth of several kilometres due to warmer inflow from low latitudes.

Yet we don’t know exactly if this is an independent development or if there are links to the sea ice decrease,” explains Professor Ursula Schauer. The goal of DAMOCLES is the exact quantification of the interplay of various influences. This is a prerequisite to improve climate models, which finally will enable more reliable predictions of future climate.