Propagation of subinertial variations in the Soya Warm Current revealed by HF ocean radars

Abstract

Propagation of subinertial variations in the Soya Warm Current (SWC), which flows through the Soya Strait located between Hokkaido, Japan and Sakhalin Island, Russia, is investigated using data from HF ocean radars together with in situ observations, such as bottom-mounted acoustic Doppler current profilers (ADCPs) and coastal tide gauges. The subinertial variations with periods from 5 to 20 days were captured by the HF radars. The subinertial variations were significantly correlated with the meridional wind stress component over the region, suggesting that the sea level difference through the strait caused by wind-generated coastally-trapped waves on the east coast of Sakhalin and west coast of Hokkaido are considered to be a possible mechanism casing the subinertial variations in the SWC. Propagation of the subinertial variations was also clearly captured by the HF radars. The estimated phase velocity suggests that the subinertial variations propagate downstream along the coast as the 3rd-mode barotropic continental shelf waves.