Spatial and temporal variability of the Kuroshio water based on a net work of the long-term repeat sections

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Downstream changes of the transport and water characteristics of the Kuroshio were investigated with the long-term repeat hydrographic sections. We also use the new climatological data constructed by our group and the high-resolution hydrograhic data obtained by our extensive survey of the Kuroshio by R/V Hakuho Maru, the cruise KH-96-4. The main results are as follows.1. Long-term mean geostrophic fluxes of the Kuroshio relative to 800 dbar or 1000 dbar were calculated by the potentrial density classes of 0.1 siguma_<theta> interval. Ii was shown that the downstream increase of the transport from the East China Sea to the south of Japan depends on the density classes. The increase in the density classes of North Pacific Subtropical Mode Water (NPSTMW) and North Pacific Intermediate Water (NPIW) is remarkable. The water of these classes shows downstream changes of the water characteristics, which indicates vigorous inflow of relatively new NPSTMW and NPIW into the Kuroshlo.2. Differences in the water characteristics of the density classes of NPSTMW and NPIW were detected, which is consistent with the previous hypothesis that the advection of these water masses from the east is severely reduced during the large-meander periods of the Kuroshio. The consistent differences in the water properties over the Kuroshio recirculation region were also detected based on our new climatological data.3. The spatial structures of the Kuroshio water, revealed by the repeat hydrographic sections described above, were confirmed and refined by the snapshot data obtained by our extensive survey, KH-96-4.