Simulated Pathways of the Northwestern Pacific Water in the Okhotsk Sea

Water exchange between the Pacific Ocean and the Okhotsk Sea through the Kuril Straits and transport of Pacific waters into and from the Okhotsk Sea are studied. These studies are based on retrospective simulation for the period from 1991 to 2000 by eddy-permitting OGCM RIAMOM and Lagrangian analysis. The volume transport occurs mainly through the seven straits, Bussol, Kruzenshtern, Friz, Ekaterina, Fourth, Nadezhda and Urup straits (in decreasing order of significance). These straits were shown to be responsible for about 95% of total water exchange. We found that the contribution of the Bussol and Kruzenshtern straits in the ocean-sea exchange was considerably overestimated previously. In the active upper 200 m layer, the contribution of the Fourth, Friz and Ekaterina straits is comparable with that of the Kruzenshtern and Bussol straits. Estimations of the depth-integrated transport and transport in the representative model layers in different seasons show that the Northwestern Pacific Water enters the Okhotsk Sea mainly through the northern Kuril Straits, namely, the Kruzenshtern and Fourth straits. The Okhotsk Sea Mode Water flows from the Sea in the upper 200 m layer mainly through the Friz, Ekaterina, Bussol and Urup straits (in decreasing order of significance). Lagrangian simulation reveals the main transport pathways of ocean water into and from the Okhotsk Sea. In the surface and near surface layers, this water is transported to the northwestern shelf of the Sea by the West Kamchatka Current (especially in winter and spring) and by the over slope branch of the North Okhotsk Current. Then it is transferred by the coastal branch of the North Okhotsk Current and flows into the East Sakhalin Current. At depth below 200 m, the ocean water does not reach the northern shelf anyway. At depths of 500 m and deeper, the water exchange between the ocean and the Okhotsk Sea is insignificant because of weak currents at such depths. The simulation results are found to be in a reasonable agreement with instrumental measurements and satellite data.