Ocean color variability in the Tasman Sea

Abstract

The Tasman Sea contains the largest noncoastal surface chlorophyll‐a concentrations within the South Pacific Ocean. Observations of ocean color from SeaWiFS demonstrate that the chlorophyll‐a seasonal cycle is characterized by a large austral spring bloom and a much smaller fall bloom separated by periods of lower concentrations, typical of communities within the North Atlantic Ocean. However, the seasonal cycle of the mixed layer depth of the Tasman Sea is much more similar to the North Pacific Ocean, whose persistent winter stratification results in relatively constant chloropohyll‐a concentrations. Examination of eddy kinetic energy from satellite altimetry (TOPEX/Poseidon and ERS‐2 blended product) reveals that the western Tasman Sea contains a large number of eddies originating within the East Australian Current that coincide spatially with the blooms. Upwelling and downwelling associated with these eddies greatly increase vertical mixing within the upper ocean, offsetting the normally shallow winter mixed layer, which leads to a chlorophyll‐a seasonal cycle much like that of the North Atlantic Ocean.