Seasonal atmospheric response to Arctic sea-ice loss

Arctic sea-ice plays an important role on the North Hemisphere climate. However, anthropogenic climate change has caused a decline in sea-ice, leading to a higher increase in surface temperatures over the Arctic than at global scale. To analyse how sea-ice loss can affect mid-latitude climate in different seasons, a set of sensitivity experiments performed with the European Consortium Earth-system model (EC-EARTH) version 3P have been analysed, considering standard resolution (SR) and high resolution (HR) configurations. By changing the sea-ice albedo to open-ocean value, sea-ice concentration (SIC) is artificially reduced. The SIC loss is largest during summer and autumn (reaching 80%), consistent with the maximum solar radiation in the seasonal cycle, but still considerable (up to 20-30%) during spring and winter in regions around the sea-ice edge. Surface temperature shows strong positive anomalies over the Arctic in spring and autumn, and positive anomalies over the Hudson Bay in most of the seasons; also, temperature raises 1-1.5 ºC over the northern part of the American and Eurasian continents. Mean sea level pressure robustly decreases over the Hudson Bay, and shows a negative North Atlantic Oscillation (NAO)-like pattern in winter but is not robust. Weak but robust positive precipitation anomalies are found over the Arctic regions. Zonal-mean temperature displays a shallow warming response related to sea-ice loss, with the exception of winter in HR that also shows a lower-stratospheric warming. A mid-stratospheric cooling is robustly found during summer in both model resolutions, probably associated with a reduction of shortwave radiation back to space.