Winter Precipitation Responses to Projected Arctic Sea-Ice Loss and Global Ocean Warming and Their Opposing Influences over Northeast Atlantic region

Abstract

Using a large ensemble of simulations from the Polar Amplification Model Intercomparison Project (PAMIP) and Coupled Model Intercomparison Project Phase 6 (CMIP6), we compare the response of winter-mean precipitation and daily extremes across the North Hemisphere in response to future Arctic sea-ice loss and global ocean warming. North Atlantic is simulated to become drier in response to future Arctic sea-ice loss, with reduced precipitation intensity and more dry days. A wetting response to sea-ice loss is simulated over the midlatitude Atlantic Ocean. These responses are robust across the eight models analysed, albeit with differences in their magnitude and spatial pattern. The precipitation response to global ocean warming is broadly opposite in sign, but larger in magnitude, compared to the response to sea-ice loss, over these regions. The precipitation responses to both sea-ice loss and ocean warming are strongly related to coincident changes in storm density and intensity. More specifically, there is an equatorward shift of the North Atlantic storm track in response to sea-ice loss, and northeastern extension of the North Atlantic storm track and weakening of Mediterranean storm track in response to ocean warming. The linear combination of the responses of future Arctic sea-ice loss and global ocean warming explain well the spatial pattern of the precipitation change at 2 °C global warming projected in CMIP6. Our results suggest that projected future precipitation change over North Atlantic reflects a ‘tug-of-war’ between Arctic sea-ice loss and global ocean warming, but the latter dominates over the former.