宗谷暖流の季節変動

抄録

Seasonal variation of Soya Current along the Hokkaido coast in the Sea of Okhotsk was investigated both by the long-term current record obtained at the moored station off Sarufutsu and adjusted sea level record at the tidal stations along the Hokkaido coast. The current record shows significant seasonal variation, i.e., strong in summer and weak in winter. The current variation is closely correlated with the sea level difference between by high sea level in the Japan Sea compared with that in Sea of Okhotsk, while the weak current in winter is due to small difference of the sea level between both seas. This fact strongly depends on the unique seasonal variation of the sea level along the Hokkaido coast in the Sea of Okhotsk, i.e., maximum in winter and minimum in spring. The high sea level in winter is retained by the low salinity water in the subsurface layer of the southern part of the Sea of Okhotsk (Ito, 1997) and found along the southern coast of Hokkaido. The interannual variation of sea level along the Hokkaido coast in the Sea of Okhotsk in winter correlates with the Monsoon-Index (MOI) variation defined as difference of atmosphere pressure between Irkutsk in Russia and Nemuro in Hokkaido.