Variability and Energetics of the Kuroshio Extension and Its Recirculation Gyre from the First Two-Year TOPEX Data

Abstract

Abstract Altimetry data from the first 21-month TOPEX mission (September 1992–June 1994) are analysed to investigate the sea surface height (SSH) fluctuations in the Kuroshio Extension and its southern recirculation gyre regions (25°–40°N, 136°E–180°). To separate the time-dependent (SSH) signals associated with the Kuroshio Extension from those associated with the westward recirculating flows, and to study the energetics of these currents, the author first estimated the mean SSH profiles along individual ground tracks by assuming the velocity profile of the Kuroshio Extension to be Gaussian shaped and by successively fitting the synthetic current's height profile to the time-dependent SSH data. The mean SSH field, including the influence from the recirculating flows, is then derived through the constraint from climatological hydrographic data. During the 21-month period of the TOPEX mission, the eddy kinetic energy (EKE) of the Kuroshio Extension had relatively uniform values during three separate stages...