IUGG 2003 Abstract

P01 Western Boundary Currents Friday, July 4 AM Location: Site B, Room 18 Presiding Chairs:H. Ichikawa, S. Imawaki

TIME [ 1040 ] [ P01/04A/B18-006 ]

TIME SERIES OF BAROCLINIC TRANSPORT OF THE KUROSHIO SOUTH OF JAPAN ESTIMATED BY INVERTED ECHO SOUNDERS

Koji KAKINOKI(Department of Earth System Science & Technology, Interdisciplinary Graduate School of Engineering Sciences)

Hiroshi UCHIDA(Japan Marine Science and Technology Center, Japan) Shiro IMAWAKI ( Research Institute for Applied Mechanics, Kyushu University, Japan ) Shin-ichiro UMATANI ( Research Institute for Applied Mechanics, Kyushu University, Japan ) Hiroshi ICHIKAWA ( Faculty of Fisheries, Kagoshima University, Japan ) Mark WIMBUSH ( Graduate School of Oceanography, University of Rhode Island, USA )

The Kuroshio is the western boundary current associated with the subtropical gyre of the North Pacific. The Kuroshio plays a significant part in the earth′s climate through the northward transport of mass and heat. In 1993-1995, the ASUKA (Affiliated Surveys of the Kuroshio off Cape Ashizuri) group carried out intensive oceanographic observations of the Kuroshio south of Japan, including direct current measurements and frequently repeated hydrographic surveys along subsatellite track of TOPEX/POSEIDON. They obtained a time series of the Kuroshio transport for upper 1,000 m over nine years (1993-2001) by combining these in-situ data and altimeter data. To better understand the estimate variation of the Kuroshio transport, we need to estimate the variation of baroclinic transport associated with density fluctuation accurately. Inverted Echo Sounders (IESs) have been maintained on both the coastal side and offshore side of the Kuroshio since the ASUKA intensive survey. The IES is moored on the sea floor and measures round-trip acoustic travel time between the sea floor and the sea surface. It is known that a linear relationship exists between the acoustic travel time and depth of the main thermocline, and also that the gravest empirical mode (GEM) can relate the acoustic travel time to vertical profiles of temperature. In this study, we obtain a 10-year long time series of the sea-surface dynamic height anomaly on each side of the Kuroshio, applying the GEM method. A time series of baroclinic transport of the Kuroshio is estimated from those dynamic height anomaly data. The estimated dynamic height anomaly on each side agrees well with dynamic height anomaly calculated from hydrographic data.