Seasonal and Inter-Annual Variability of Wind-Driven Upwelling near the East Coast of Sakhalin Island Based on QuikSCAT/SeaWinds Scatterometer Data

Abstract

In this paper, seasonal and interannual upwelling variability in the Sea of Okhotsk off the eastern coast of Sakhalin Island based on wind data obtained using the QuikSCAT/SeaWinds scatterometer (1999–2009) were studied. The upwelling strength was estimated from the magnitude of the wind-induced Ekman transport directed away from the coast (upwelling index). The obtained results show that upwelling near the eastern coast of Sakhalin Island is mainly associated with summer southerly monsoon winds over the Sea of Okhotsk. In the northern and central parts of the East Sakhalin shelf, upwelling is observed in July–August. In the southern part of the region, off the coast of Cape Patience, it begins in August and continues until September. The variability in the duration and strength of upwelling is due to regional features of the wind forcing. Ekman transfer and pumping contribute approximately equally to the upwelling generation. This shows that upwelling associated with the spatial inhomogeneity of the wind stress vorticity can affect the decrease in water temperature off the eastern coast of Sakhalin Island. The seasonal variability of the southern monsoon winds favorable for the development of upwelling is largely determined by the summer Okhotsk anticyclone (atmospheric center of high pressure over the Sea of Okhotsk). The latter is characterized by significant interannual variability. Its interannual variations correlate well with the upwelling strength near the eastern coast of the island. Upwelling decreases in years with negative atmospheric pressure anomalies in the Okhotsk anticyclone, while enhanced upwelling is associated with a well-developed positive anomaly of this regional high-pressure center.