Predominant modes of winter surface wind variability over the Gulf of Alaska

Abstract

AbstractTwo distinct modes extracted from winter (Dec.–Mar.) monthly mean surface wind variability over the Gulf of Alaska (GOA) and part of the northeast Pacific Ocean have been identified along with their associations with sea surface temperature (SST), coastal downwelling, surface air temperature (SAT) and sea level pressure (SLP). The leading mode of surface wind variability, accounting for 45% of the variance, is characterized by two distinct and alternating modes or their linear combination, and shows strong interannual and interdecadal variations with the transition years in the mid‐1970s and the beginning and late of 1990s. One mode (M1) features a coherent cyclonic or anticyclonic surface wind anomaly in the GOA and part of the northeast Pacific Ocean, and reflects wind field variability related to the intensity of large scale atmosphere‐ocean interactions associated with the Aleutian Low, the Pacific/North American (PNA) pattern, the Pacific decadal oscillation (PDO), and the South Oscillation (SO). This mode significantly influences SAT over the GOA and the entire northeast Pacific and influences downwelling along the eastern and southeastern GOA. It does not significantly influence SST in the northern GOA. The other (M2) characterizes dominant southerly or northerly anomalies, and significantly influences coastal downwelling in the northern and southeastern GOA. It is also correlated with SAT over the GOA, the Bering Sea shelf, and much of Alaska. The impact of M2 on SST is greater than that of M1 in the GOA and the Bering Sea. M1 and M2, respectively, correspond to the PNA pattern and a dipole pattern, and the later is characterized by the third mode of the empirical orthogonal function (EOF) analysis of winter SLP variability over the domain 20° –70°N and 160°E–100°W, accounting for 13% of the variance. The dipole pattern is a new mode of winter atmospheric variability, with opposite anomalous centres over the southern Bering Sea and the west coast of the USA and part of the northeast Pacific Ocean. Copyright © 2009 Royal Meteorological Society