Basic study on baroclinic variations of the Kuroshio estimated from IES data

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Vertical profiles of temperature and salinity are estimated by the GEM (gravest empirical mode) method from the IESs (inverted echo sounders) data deployed on coastal and offshore sites off cape Ashizuri, and then sea-surface dynamic height (SSDH) are calculated from those profiles. From difference of these SSDHs, a time series of baroclinic transport of the Kuroshio between these two stations are obtained. The IES-derived SSDH is compared with CTD-derived one ; the rms (root-mean-square) difference is 3.2 cm on the coastal site and 2.5 cm on the offshore site. Meanwhile, comparison between the SSDH anomaly derived from the CTD data and that obtained from the satellite altimetry data results in 3.6 cm and 2.9 cm rms differences on the coastal and offshore sites, respectively. These results confirm that the SSDH determined from the CTD data is closer to that of the IES data than that of the altimetry data. In addition, the steric height component confined in the surface-layer is estimated from the CTD vertical temperature profile as 5 cm in the altimetry but only 2 cm for the IES data.We also continued to add description on variations of the Kuroshio and to prepare dataset being compared with the IES data. In particular, hydrographic data along the ASUKA observational line off Shikoku are acquired by KT05-23 cruise on R/V Tanseimaru, and the period of the time series is expanded for variations of the Kuroshio axis position estimated from the surface velocity field obtained by combining the altimetry data and surface drifter data. Especially, the latter reveals that variations of the baroclinic transport of the Kuroshio obtained by the IES data are strongly influenced by variations of the Kuroshio axis position.We made a summary report on our achievements during this 3-year period.