Prediction of phytoplankton growth in a Warm-Core Ring using three dimensional ecosystem model

Abstract

In order to simulate the response of the primary production dynamics to the decay of the Warm-Core Ring (WCR) 86-B off the east coast of Japan, we made a numerical model which consists of a three dimensional physical model (modified GCM) and we used the same biological model that Frankset al. (1986) did. According to the three dimensional model, the well known sub-surface chlorophyll maximum was reproduced but horizontal distributions of Chl.a and NO₃ ⁻-N showed different patterns corresponding to different initial conditions of nutrient. This is because the weak vertical velocity in the WCR does not play an important role on the ecosystem but only the light intensity and the balance between uptake and vertical diffusion of dissolved nutrient is important. This result differs from that of Frankset al. (1986). The two WCRs interaction model suggests that a weak upwelling could exist between two WCRs accompanied by baroclinic instability.