CSIRO Marine and Atmospheric Research
Past Seminars

11.30 am, Tuesday 18 November 2003 (Tas time)

CSIRO Auditorium, Hobart

K Katsumata
University of NSW at ADFA

Water exchange and tidal currents through the Bussol Strait
revealed by direct current measurements

The Sea of Okhotsk is a marginal sea of the North Pacific. Recent observations point out its unique role in ventilating the intermediate layer of the Pacific. It is this ventilation that forms the salinity minimum in the Pacific known as the North Pacific Intermediate Water. ‘Transports’ between these two basins is, however, hardly known. This seminar provides results from an intensive survey in Bussol Strait, the main connection point between the Okhotsk Sea and the North Pacific.

Yo-yo casts of a lowered acoustic Doppler current profiler were performed at 13 stations across the narrowest part of the strait. Time series covering no less than 25 hours were obtained for each station and the semi-diurnal and diurnal tides were separated. The diurnal tide at the spring tide shows a remarkable peak of the amplitude of 1.1 metres per second at the depth below 1,000 metres in the western channel of the strait. The upper part of the residual component flows toward the Pacific and the lower part flows in the opposite direction. The outflow is in excess of the inflow and net transport through the strait is 8.2 to 8.8 Sv. Outflow is strong in two density ranges. The upper peak around 26.8 sigma-theta corresponds to the density of North Pacific Intermediate Water. Heat and salt transports through the strait are also calculated. Based on these, net heat and salt exchanges between the Sea of Okhotsk and the North Pacific are estimated - net heat flux of -34 TW and net salt flux of -1.9 ton/s are exchanged from the Sea of Okhotsk to the North Pacific.

[Authors: K. Katsumata (UNSW at ADFA), K. I. Ohshima (Hokkaido University),
T. Kono (Hokkaido Tokai University), M. Itoh (Japan Marine Science and Technology Center),
I. Yasuda (University of Tokyo), M. Wakatsuchi (Hokkaido University)]

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