Near‐surface circulation and tidal currents of the Okhotsk Sea observed with satellite‐tracked drifters

Abstract

Near‐surface circulation of the Okhotsk Sea was observed with ARGOS drifters from August 1999 to February 2000. The drifters clearly revealed the existence of the southward boundary current (the East Sakhalin Current) off the east Sakhalin. This current is strongly controlled by bottom topography and confined to the region shallower than 1000 m. The volume transport of this current is estimated to be in the range of 4–9 Sv (1 Sv = 106m3 s−1), with the increase from summer to winter. The current appears to consist of two cores: one exists near the coast (50–150 m depths) with typical speeds of 0.3–0.4 m s−1 and the other exists over the shelf slope (300–900 m depths) with typical speeds of 0.2–0.3 m s−1. A part of this southward current continues as far as the southern tip of Sakhalin Island, while another part turns to the east around Terpeniya Bay (∼48°N) flowing eastward as far as Bussol' Strait. Most of the drifters that survived in the Okhotsk Sea went out to the Pacific through Bussol' Strait by less than a half year, suggesting that Bussol' Strait is the main pathway for the surface water to flow out from the Okhotsk Sea. Mesoscale anticyclonic eddies with diameters of 100–200 km are dominant in the Kuril Basin. Diurnal shelf waves were identified over the shelf in the northern part of the east Sakhalin shelf. Large amplification of diurnal tidal currents (order of 1.0 m s−1) was observed over Kashevarov Bank along with the residual anticyclonic circulation. Both diurnal and semidiurnal tidal currents were found to be enhanced in and around Bussol' Strait.