TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 51 (No. 4), pp. 471-488, 1995

Modeling of Spring Bloom in the Western Subarctic Pacific (off Japan) with Observed Vertical Density Structure

A. Yoshimori1, J. Ishizaka2, T. Kono3, H. Kasai3, H. Saito3, M. J. Kishi4 and S. Taguchi3

1Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-01, Japan
2National Institute for Resources and Environment, Tsukuba 305, Japan
3Hokkaido National Fisheries Research Institute, 116 Katsurakoi, Kushiro 085, Japan
4Ocean Research Institute, University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164, Japan

(Received 22 September 1994; in revised form 12 January 1995; accepted 8 March 1995)

Abstract: Effects of vertical stability on spring blooms of phytoplankton were investigated for the western subarctic Pacific ocean using a one-dimensional (depth) ecosystem model. In the model, vertical stability was expressed by diffusion constants calculated from observed density distribution. Dynamics of phytoplankton in blooms was calculated by the model using the vertical diffusion. Then, the calculated results were compared with the Coastal Zone Color Scanner (CZCS) data. The comparison shows that the shallow surface mixed layer causes early start days of spring blooms at inshore (northern) stations. In addition, spring blooms continue long at inshore (northern) stations since a water column has weak stability. This is because weak stability of a water column causes large nutrient supply from a deep layer and large diffusive transport of phytoplankton biomass from the subsurface maximum.

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