The Northeastward current southeast of Okinawa Island observed during November 2000 to August 2001

Abstract

In order to estimate the variability of current structure and mean geostrophic volume transport in the southeast of Okinawa Island, the round‐trip acoustic travel times between sea bottom and surface at nine sites were measured by Inverted Echo Sounder with pressure gauge (PIES) from November 2000 to August 2001. Vertical sections of geostrophic velocity are calculated by using vertical profiles of specific volume anomaly derived by the Gravest Empirical Mode method from the PIES data. In the upper 500 m layer over a slope shallower than 1000 m depth, the northeastward current reached up to 60 cm s −1 during the occupation of an anticyclonic eddy, and decreased to −15 cm s −1 during the occupation of a cyclonic eddy, around the mean of 20 cm s −1 . The temporal mean geostrophic volume transport relative to the 2000 dbar level was estimated to be 6.1 Sv (1 Sv ≡ 10 6 m 3 s −1 ) northeastward in the west of 128.85°E.