Characteristics of the cold-water belt formed off Soya Warm Current

We examined the data obtained by acoustic Doppler current profiler, conductivity-temperature-depth profiler, and expendable bathythermograph observations, which were collected in the summers of 2000, 2001, and 2002, to clarify the characteristics of the cold-water belt (CWB), i. e., lower-temperature water than the surrounding water extending from the southwest coast of Sakhalin along the offshore side of Soya Warm Current (SWC) and to confirm one of the formation mechanisms of the CWB as suggested by our previous study, i. e., the upwelling due to the convergence of bottom Ekman transport off the SWC region. The CWB was observed at about 30 km off the coast, having a thickness of 14 m and a minimum temperature of 12 degrees C at the sea surface. The CWB does not have the specific water mass, but is constituted of three representative water types off the northeast coast of Hokkaido in summer, i. e., SWC water, Fresh Surface Okhotsk Sea Water, and Okhotsk Sea Intermediate Water. In a comparison of the horizontal distributions of current and temperature, the CWB region is found to be advected to the southeast at an average of 40 +/- 29% of the maximum current velocity of the SWC. The pumping speed due to the convergence of the bottom Ekman transport is estimated as (1.5 -3.0) x 10(-4) m s(-1). We examined the mixing ratio of the CWB, and the results implied that the water mass of the CWB is advected southeastward and mixes with a water mass upwelling in a different region off SWC.