Impact of decreasing sea ice cover and warming Arctic surface temperature on the Northern mid-latitude climate – comparison of coupled with uncoupled EC-Earth simulationsud

摘要

Idealized atmosphere-only simulations with reduced and removed Arctic sea-ice cover and increased Arctic surface temperatures are compared with fully coupled atmosphere-ocean-sea-ice simulations for 1850-2100 including increases in greenhouse gas and aerosol concentrations. While the uncoupled simulations only contain surface forcing in the areas of Arctic sea-ice of the reference simulation, the coupled simulations show warming over the whole globe although in the Arctic the strongest signal occurs in all seasons but summer. A warming of more than 21 °C over the northern Barents Sea in winter 2001-2100 compared to winter 1851-1950 is simulated according to the strong RCP 8.5 scenario. The weakest warming within the area north of 40 ºN can be seen south of Greenland and Iceland with even a slight cooling simulated in spring according to the moderate RCP 4.5 scenario, due to a weakened Atlantic Meridional Overturning Circulation. Common sea level pressure responses between the idealized sensitivity studies and the coupled simulations are decreases in the Central and Western Arctic. While in the idealized studies sea level pressure increases can be seen over Eastern Europe, increases in the coupled simulations occur over Ireland and the UK or west thereof.