Modelling mixed layer depth and plankton biomass off the west coast of South Island, New Zealand

Abstract

Abstract 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 data for 1980–1993 is compared with measurements from several research voyages, and with a sea surface temperature dataset analysed from in situ and satellite data. The model produces a realistic seasonal cycle in sea surface temperature, mixed layer depth and surface nitrate concentration. There is a pronounced spring maximum in the modelled phytoplankton biomass. Owing to a lack of data in late spring, this cannot be confirmed by observations, but in other respects the model agrees well with measurements.