Profiling float measurements of the recirculation gyre south of the Kuroshio Extension in May to November 2004

Abstract

During May to November 2004, 20 profiling floats were deployed in the recirculation gyre (RG) region south of the Kuroshio Extension (KE). With the KE and RG being in a stable state, most of these floats remained within the RG, resulting in a large number of satellite position fixes for estimating the velocities at the parking depth (1500 db) and a large number of temperature/salinity profiles for estimating the geostrophic velocities above the parking depth. The flows of the RG at different depths in the upper 1500 db are found to be approximately parallel to each other, with the speed at the surface (35 cm. s-1) being about three and a half times larger than that at the parking depth (10 cm s-1). By analyzing the full-depth conductivity-temperature-depth profiles in the RG, in addition to the velocity estimates, we found that the vertical structure of the RG velocity field was dominated by the barotropic and first baroclinic modes. The two modes are combined in such a way that the resulting RG circulates anticyclonically in the same direction from the surface to the bottom and has an anticyclonic bottom velocity on the order of 5 cm s-1. From the barotropic component (depth-averaged) of the RG velocity field, the RG transport with one standard error is estimated at 101 ± 8 × 106 m3 s-1. Copyright 2007 by the American Geophysical Union.