Journal of Oceanography, Vol. 63 (No. 2), pp. 243-253, 2007
Hideyuki Kawamura1*, Jong-Hwan Yoon2 and Toshimichi Ito1
1Research Group for Environmental Science, Division of Environment and Radiation Sciences, Japan Atomic Energy Agency, Shirakata-shirane, Tokai-mura, Ibaraki 319-1195, Japan
2Dynamics Simulation Research Center, Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
(Received 19 May 2006; in revised form 26 October 2006; accepted 26 October 2006)
Abstract: Water masses in the subsurface and the intermediate layer are actively formed due to strong winter convection in the Japan Sea. It is probable that some fraction of pollution is carried into the layer below the sea surface together with these water masses, so it is important to estimate the formation rate and turnover time of water masses to study the fate of pollutants. The present study estimates the annual formation rate and the turnover time of water masses using a three-dimensional ocean circulation model and a particle chasing method. The total annual formation rate of water masses below the sea surface amounted to about 3.53 ± 0.55 Sv in the Japan Sea. Regarding representative intermediate water masses, the annual formation rate of the Upper portion of the Japan Sea Proper Water (UJSPW) and the Japan Sea Intermediate Water (JSIW) were estimated to be about 0.38 ± 0.11 and 1.43 ± 0.16 Sv, respectively, although there was little evidence of the formation of deeper water masses below a depth of about 1500 m in a numerical experiment. An estimate of turnover time shows that the UJSPW and the JSIW circulate in the intermediate layer of the Japan Sea with timescales of about 22.1 and 2.2 years, respectively.