IMPACT OF REMOVED ARCTIC SUMMER SEA ICE ON ATMOSPHERE AND OCEAN CIRCULATION IN AN ENSEMBLE OF COUPLED MODEL SIMULATIONS

Arctic sea ice has undergone substantial decline in the last 3 decades and climate model studies show that Arctic could be ice-free in the late summer even by the middle of this century. Sea ice plays an important role in the climate system, therefore, it is important to investigate the sole influence of the Arctic sea ice loss on the atmosphere and ocean circulations. In the present study, results of the experiments carried out with the coupled global model ECHAM6-FESOM were analyzed. In an ensemble of 100 members, Arctic sea ice thickness was reduced by 80% on 1st of June in the sensitivity experiments, and changes through the following year were compared to the reference experiments. The reduction in the Arctic sea ice thickness led to an ice-free Arctic for the next 5 months in the sensitivity experiments and, as a consequence, it led to a strong increase in the surface temperature over the Arctic region in the following autumn and winter, making the response of other parameters most pronounced in those seasons. Strong baroclinic circulation anomalies were found over the Arctic, while barotropic response was found over north-eastern and southern parts of Europe. Precipitation increased over central Arctic area and also Mediterranean area in the winter, which resembles the synoptic activity shift in the same season from the northern Atlantic towards southern Europe. Changes in wind-driven ocean circulation were found in the Mediterranean Sea.