Simulated Interannual Variations of Freshwater Content and Sea Surface Height in the Beaufort Sea

The authors investigate the interannual variations of freshwater content (FWC) and sea surface height (SSH) in the Beaufort Sea, particularly their increases during 2004-09, using a coupled ice-ocean model (CIOM), adapted for the Arctic Ocean to simulate the interannual variations. The CIOM simulation exhibits a (relative) salinity minimum in the Beaufort Sea and a warm Atlantic water layer in the Arctic Ocean, which is similar to the Polar Hydrographic Climatology (PHC), and captures the observed FWC maximum in the central Beaufort Sea, and the observed variation and rapid decline of total ice concentration, over the last 30 years. The model simulations of SSH and FWC suggest a significant increase in the central Beaufort Sea during 2004-09. The simulated SSH increase is about 8 cm, while the FWC increase is about 2.5 m, with most of these increases occurring in the center of the Beaufort gyre. The authors show that these increases are due to an increased surface wind stress curl during 2004-09, which increased the FWC in the Beaufort Sea by about 0.63 m yr(-1) through Ekman pumping. Moreover, the increased surface wind is related to the interannual variation of the Arctic polar vortex at 500 hPa. During 2004-09, the polar vortex had significant weakness, which enhanced the Beaufort Sea high by affecting the frequency of synoptic weather systems in the region. In addition to the impacts of the polar vortex, enhanced melting of sea ice also contributes to the FWC increase by about 0.3 m yr(-1) during 2004-09.