Modification of the western subarctic water by exchange with the Okhotsk Sea

The flow pattern has been investigated around the Kuril Islands using data from synoptic observations in August to September 1989–1992. The Oyashio flows along the Kuril Islands, meandering around the anti-cyclonic eddies. The coastal flow of the Oyashio reaches the Hokkaido coast, while its offshore branch turns southeastward to flow northeastward along the Oyashio Front to join the Oyashio returning northeastward. The outflow from the Okhotsk Sea through Bussol’ Strait in the center of the islands is negligible or very weak, even though it exists. The change of water properties along the Oyashio has been investigated, based on T-S analysis using CTD data at densities greater than 26.8 στ. The water has already been modified when it reaches Bussolʹs Strait by mixing with Okhotsk Sea water. Okhotsk Sea water flowing out through the strait is not important for the modification. The water exchange of the Oyashio with the Okhotsk Sea and the mixing occur in a wide area around Bussol’ Strait and to the northeast. However, the modification is limited to the coastal side of the Oyashio.