Springtime North Pacific Oscillation and summer sea ice in the Beaufort sea

Abstract

We investigate the linkage between the spring (April–June) North Pacific Oscillation (NPO) and the following summer sea ice in the Beaufort sea. A positive NPO is characterized by an intensified and northeastward extended Aleutian Low, a strong Beaufort High, and enhanced easterly winds in the Beaufort sea. Concomitantly, while the deepening East Asian trough steers more cyclones from Siberia to the sub-polar Pacific and thus fewer cyclones into the western Arctic Ocean; a weak polar vortex and weak baroclinicity in the Beaufort sea does not favor cyclone activity. In addition, the East Asian trough enhances warm air advection from the Pacific to the Northwestern America. The spring NPO accounts for 29% of interannual variability of the following September sea ice cover in the Beaufort sea and can be used as a potential predictor for ice melting in the Beaufort sea. During a positive NPO, the strong easterly winds over the Beaufort sea enhance ice advection and reduce ice thickness; on the synoptic scale, there are more occurrences of the pack ice becoming detached from the coast due to the strong easterly winds. Moreover, increases in shortwave radiation and longwave radiations accelerate the ice melting.