Variability of sea ice in the Okhotsk Sea

Abstract

Sea ice in the Sea of Okhotsk is constrained by land and by season. No sea ice survives summer. The total areal extent of sea ice in winter varies interannually from approximately 1.5/spl times/10/sup 6/ km/sup 2/ to 0.8/spl times/10/sup 6/ km/sup 2/. Some results are discussed on the interannual variability of sea ice extent in the Okhotsk Sea and the SST of the eastern equatorial Pacific, which is negatively correlated with temperature of the western equatorial Pacific. Sea ice distributions are obtained by various methods such as satellite, aircraft, ship and coastal radar observations. Sea ice extent variations can be correlated with La Nina Events. The variations of atmospheric general circulation are important to explain the mechanism of the connection between La Nina events (Anti-El NIno) and the sea ice extent. El Nino events could influence the middle latitude atmospheric general circulation. Whenever El Nino events occur, Hadley circulation becomes more intense in the region of the central or western part of the north Pacific. Therefore, the middle latitude anticyclone is intensified and the middle latitude westerlies in the region of the North Pacific become more zonal. Consequently sea ice is driven by the stress of intensified westerly winds and is extended in the overall area of the Okhotsk Sea. On the other hand, when La Nina events occur, the SST is higher than it during El Nino events in the western Pacific. Sea ice drift southward to the Okhotsk Sea Coast of Hokkaido and the sea ice extent during La Nina is less than it is in normal winters. >