Mean and temporal variability in Kuroshio geostrophic transport south of Taiwan (1993-2001)

Observations of the Kuroshio south of Taiwan have been carried out on a quarterly basis since late 1992 as part of the basin-wide High Resolution expendable bathythermograph/expendable conductivity-temperature-depth (XBT/XCTD) network. Mean geostrophic transport in the Kuroshio, 0-800 m, from 34 cruises is 22.0 Sv +/- 1.5, consistent with previous results from moorings and geostrophic calculations in the upstream Kuroshio region. The mean core of the current has speed about 90 cm (-1)(S) and is located close to Taiwan. At this location the Kuroshio appears to be confined mainly to the upper 700 m, and there is no evident tight recirculation of the current. Eddy variability is substantial, and large eddies can be seen propagating westward for thousands of kilometers in TOPEX/Poseidon altimetric data, impinging on the current and altering its structure and transport. The annual range in transport is about 8 Sv +/- 6, with maximum in summer. Interannual variability is about 12 Sv +/- 6, with transport maxima in 1995 and 2000 and a minimum in 1997-1998. Interannual variability in the upstream Kuroshio may be uncorrelated with that in the downstream region south of Japan, where the transport is much greater. Our quarterly sampling aliases high frequency variability of the current, and an improved boundary-current observation program would include more frequent transects and occasional deeper measurements.