A coupled physical-biological model of a warm core ring

Abstract

A study was initiated to examine the questions: 1) Is the high phytoplankton productivity associated with warm core rings the result of a circulation associated with he frictional decay of the ring? 2) What is the relative importance of physical and biological factors in controlling production in and around the model ring? 3) Which is the more relevant grazing formulation for warm core ring plankton: that of Ivlev (1955) or that of Mayzaud and Poulet (1978)? Two biological models were formulated: a two box phytoplankton-nutrient model, and a three - box phytoplankton-zooplankton-nutrient model. The steady-state solutions of the P-Z-N model were similar with the two different grazing formulations, but the time-dependent behaviour of the two models differed markedly. The Ivlev model showed strong oscillations when the grazing pressure was high . The Mayzaud and Poulet formulation, which takes into account the changing maximum grazing rate as the zooplankton acclimate to surrounding food concentrations, showed only small, highly damped oscillations as it approached steady-state. It was felt that the Mayzaud and Poulet formulation exhibited more desirable behaviour, and was more appropriate for this model. This is the first mathematical exploration of the Mayzaud and Poulet formulation described in the literature.