MODELING MIXED-LAYER DEPTH AND PLANKTON BIOMASS OFF THE WEST-COAST OFSOUTH-ISLAND, NEW-ZEALAND

A model was developed to describe the seasonal cycles in temperature, salinity, nutrient concentration (nitrogen) and phytoplankton biomass in the upper ocean, in an area of the Tasman Sea off the west coast of South Island, New Zealand. A simulation driven by observed weather da ta for 1980-1993 is compared with measurements from several research v oyages, and with a sea surface temperature dataset analysed from in si tu and satellite data. The model produces a realistic seasonal cycle i n sea surface temperature, mixed layer depth and surface nitrate conce ntration. There is a pronounced spring maximum in the modelled phytopl ankton biomass. Owing to a lack of data in late spring, this cannot be confirmed by observations, but in other respects the model agrees wel l with measurements.