TOPEX/POSEIDON-derived space-time variations of the Kuroshio Current: applications of a gravimetric geoid and wavelet analysis

Using TOPEX/POSEIDON (T/P) altimeter data and a gravimetric geoid, we derived 7-year time-series of Kuroshio's volume transport, axis velocity, width and axis locations northeast and southeast of Taiwan. For northeastern and southeastern Taiwan, the mean volume transports are 19 and 26 Sv, the mean widths are 112 and 96 km and the mean axis velocities are 50 and 82 cm s−1, respectively. The T/P-derived volume transports agree well with in situ result. Drifter d21160 almost passes through the T/P-derived axes of the Kuroshio. The time-series show intraseasonal, semi-annual, annual and interannual variations but the frequency characteristics at the two locations are different owing to monsoon, bottom topography and other factors. Wavelet analyses show that the amplitudes and phases of the frequency components vary with time. A biennial component is found in almost all time-series and may be excited by the tropical quasi-biennial oscillation of the atmosphere. The volume transport northeast of Taiwan has a positive correlation (0.6) with ENSO with a 1-month lag, and both the volume transport and velocity southeast of Taiwan have a negative correlation (−0.6) with ENSO with a 9–10 months lead.