Seasonal characteristics of the surface mixed layer in the Australasian region: implications for primary production regimes and biogeography

The seasonal cycle of physical, chemical, and biological properties of the surface ocean mixed layer in the Australasian region ( 0 to 50 degrees S, 90 to 180 degrees E) were described on the basis of a range of data products, some of which are described for the first time. They include seasonal fields of temperature, salinity, mixed layer depth, nitrate, phosphate and silicate from the CSIRO Atlas of Regional Seas ( CARS), as well as estimates of chlorophyll from SeaWiFS ocean colour data, and a range of supplementary information taken from published studies. Seasonal chlorophyll cycles were interpreted within the context of variability in nutrient concentrations and mixed layer depths. This interpretation included a biogeographical description, which was compared with related regional and global products. Such descriptions provide a baseline for future investigations of interannual variability and long-term trends in mixed layer properties, as well as contributing to the development of spatial frameworks for management of the region's resources.