Abstract. In 1993-1995, we carried out observations of the Kuroshio south of Japan, including direct current measurements and repeated hydrographic surveys along a satellite track of the TOPEX/POSEIDON altimeter. The velocity field of the Kuroshio is determined by geostrophic calculation using the repeated hydrographic survey data, referenced to velocities observed at mid and abyssal depths. The volume transport of the Kuroshio is estimated from this velocity field. The estimated transports of the Kuroshio have a high correlation with sea-surface height differences across the Kuroshio. Having this relationship and using the altimeter data, we obtained a time series of the Kuroshio transport over seven years at ten-day intervals. The Kuroshio transport, excluding contributions by local recirculations, is estimated to be 42 x 10 6 m3/sec on average. The correlation between sea-surface height difference and transport provides a practical method of long-term monitoring of the Kuroshio transport using satellite altimetry.

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[1] The Affiliated Surveys of the Kuroshio off Ashizuri-Misaki (ASUKA) project is a collaboration between scientists in Japan and the United States to improve our understanding of the structure and dynamics of the Kuroshio off the coast of southwest Japan. In this project an array of nine inverted echo sounders and nine current meter moorings were deployed for 2 years (1993)(1994)(1995) along a line extending 1000 km from Shikoku. Numerous hydrographic profiles along this section were used to determine the regional gravest empirical modes (GEMs), which relate vertical profiles of temperature and specific volume anomaly to vertical acoustic echo time. These GEMs were used in conjunction with the inverted echo sounder data to calculate 2-year time series of entire sections of relative geostrophic velocity and temperature. Current meter data provided absolute velocity references for the geostrophic velocity sections. In addition, a time series of Kuroshio position was determined from the GEM temperature sections. It shows three big (>80 km displacement) and three little offshore meanders of the Kuroshio occurring in February, May/June, and October of both years. This suggests a 4-month periodicity, possibly phase-locked to the annual cycle. The meanders may be caused by mesoscale eddies arriving from the east. The observed meanders were preceded by low Kuroshio volume transport and were followed by high Kuroshio volume transport. The Kuroshio volume and temperature transports were highly variable, with respective means of 65 ± 4 Sv and 3.7 ± 0.2 PW and standard deviations of 20 Sv and 0.9 PW.INDEX TERMS: 4576

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Combining surface drifter and satellite altimeter data,we estimate Eulerian mean sea‐surface velocity with a resolution of quarter degrees in both latitude and longitude. The Eulerian mean velocity is calculated by subtracting the altimeter‐derived velocity anomaly (i.e., deviation from the temporal mean) at the time when a drifter measured the surface velocity, from this drifter‐measured velocity. The method is applied to the surface flow of the North Pacific, using TOPEX/POSEIDON and ERS‐1/2 altimeter data, and WOCE‐TOGA surface drifter data obtained during October 1992 to January 2001. The estimated Eulerian mean velocities for the Kuroshio south of Japan and the Kuroshio Extension region tend to be smaller than simple averages of drifter‐derived velocities by 20 to 50 cm sec−1. The instantaneous velocities are obtained every ten days as sums of the Eulerian mean velocities and velocity anomalies. They agree well with in situ surface velocities measured by acoustic Doppler current profilers.

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