Transport |
Transports per unit depth (TPUD) are calculated at two mid-depths, 650 and 1500 m, and at the sea surface.
It is estimated by integrating the velocity component normal to the ASUKA-line from the coast to the offshore edge of the eastward flowing surface Kuroshio, which is determined from Topex/Poseidon (T/P) altimeter data shown as a white line in the last figure in variability.html.
TPUD of the Kuroshio is estimated to be 60 to 170 Sv/km at the surface, 15 to 70 Sv/km at 650 m depth, and -5 to 20 Sv/km at 1500 m depth (Sv=106m3s-1).
The correlation coefficient between the sea surface and 650 m depth is very high, 0.92. This suggests that the horizontal structure along the ASUKA line is vertically coherent from the sea surface to 650 m depth.
The correlation between the other depths is not high. One reason of this low correlation is the
occasional presence of westward flow at 1500 m depth.
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Time series of TPUD of the Kuroshio. The upper, middle, and lower lines indicate TPUD at the sea surface, 650 m, and 1500 m depth, respectively. The upper line is estimated from T/P altimeter data; lower lines are estimated from current meters. The transport of recirculation due to the coastal cyclonic eddy is subtracted by fixing the onshore extent to the coast. The solid circles indicate cases when accurate estimates are obtained for all the three layers. The dotted line indicates cases
when horizontally interpolated data are used for the missing array of second year CM08, which locates near the offshore edge of the Kuroshio most of the time when it meanders, while the solid line indicates no interpolation for CM08 required.
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Scatter diagrams of TPUD of the Kuroshio. All the data used are the same as those shown by solid circles above. Left (middle) panel shows the diagram between the values at the sea surface and 650 m (1500 m) depth. The right shows that for the 650 m and 1500 m depths. The solid line is the regression line.
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