Journal of Oceanography, Vol. 62 (No. 5), pp. 731-744, 2006
Hiroshi Kuroda1*, Yutaka Isoda2, Hidetaka Takeoka3 and Satoshi Honda4
1National Research Institute of Fisheries Science, Sanbashi-dori, Kochi 780-8010, Japan
2Graduate School of Fisheries Science, Hokkaido University, Minato-cho, Hakodate, Hokkaido 041-8611, Japan
3Center for Marine Environmental Studies, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
4Hokkaido National Fisheries Research Institute, Katsurakoi, Kushiro, Hokkaido 085-0802, Japan
(Received 17 October 2005; in revised form 22 March 2006; accepted 6 June 2006)
Abstract: In order to examine seasonal variation in a coastal current and the dynamics of the current, we carried out a mooring current measurement near the coast on the eastern shelf of Hidaka Bay from December 2002 to July 2003. There seemed to be two current regimes during the observed period; one a southeastward current from December to March, and the other a northwestward current after April. Arrested topographic wave dynamics was used to understand along-shore steady momentum balance at the mooring site. It was found that the friction term was negligible during the former regime, that is, the wind stress term roughly counterbalanced the pressure gradient term. On the other hand, the contribution of each term to the momentum balance was sensitive to the resistance coefficient value during the latter regime. A numerical study showed that wind forcing alone could not reproduce the observed current velocity and momentum balance during the former regime. One possible interpretation of the observed results is superposition of the arrested topographic waves forced by the along-shore wind stress and downstream extension of the Coastal Oyashio. Numerical experiments using combined forcing of the wind stress and an inflow associated with the Coastal Oyashio supported the expected dynamics.