An inverse method for estimating absolute velocities of the Kuroshio

An inverse method for estimating absolute velocities of the Kuroshio in the East China Sea and south of Japan was applied using hydrographic section data collected from January 19 to February 27 2006. By assuming the water mass to be conserved in four computational boxes, an undetermined system of linear equations was built. A family of solutions was firstly obtained by the “tapered least squares” method and then the optimal solution was selected based on two principles which are no large absolute velocities in deep layer and small residuals remained. The inversion results showed a good mass conservation and the residuals in each layer were below 1.50 Sv (1 Sv=10⁶ m³s⁻¹). The absolute velocities in the deep part of the computational region were below 0.01ms⁻¹. The maximum velocities of the Kuroshio calculated by the inverse method were 1.06 ms⁻¹ at Tokara Strait and 1.48 ms⁻¹ at south of Japan. The net volume transports of the Kuroshio in PN section and TK section were 24.23 Sv and 22.76 Sv, respectively.