TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 63 (No. 4), pp. 573-588, 2007

Seasonal Variations of Water System Distribution and Flow Patterns in the Southern Sea Area of Hokkaido, Japan

Ana Luisa Rosa1*, Yutaka Isoda1, Kazuyuki Uehara2 and Tomokazu Aiki1

1Graduate School of Fisheries Sciences, Hokkaido University, Minato-cho, Hakodate 041-8611, Japan
2Fisheries Research Agency, Fukuura, Kanazawa-ku, Yokohama 236-8648, Japan

(Received 12 June 2006; in revised form 13 January 2007; accepted 19 February 2007)

Abstract: Hydrographic data and composite current velocity data (ADCP and GEK) were used to examine the seasonal variations of upper-ocean flow in the southern sea area of Hokkaido, which includes the "off-Doto" and "Hidaka Bay" areas separated by Cape Erimo. During the heating season (April–September), the outflow of the Tsugaru Warm Current (TWC) from the Tsugaru Strait first extends north-eastward, and then one branch of TWC turns to the west along the shelf slope after it approaches the Hidaka Shelf. The main flow of TWC evolves continuously, extending eastward as far as the area off Cape Erimo. In the late cooling season (January–March), part of the Oyashio enters Hidaka Bay along the shallower part of the shelf slope through the area off Cape Erimo, replacing almost all of the TWC water, and hence the TWC devolves. It is suggested that the bottom-controlled barotropic flow of the Oyashio, which may be caused by the small density difference between the Oyashio and the TWC waters and the southward migration of main front of TWC, permits the Oyashio water to intrude along the Hidaka shelf slope.

*Corresponding author E-mail: ana@sola3.fish.hokudai.ac.jp

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