Modeling the physical and biogeochemical response of a marine shelf system to a tropical cyclone

Abstract

We describe the first use of a fully integrated biogeochemical model to explore the response of a marine shelf system to a tropical cyclone. Ocean currents, nutrients, sediments and plankton dynamics were simulated under conditions representative of Tropical Cyclone Bobby, which traversed the Australian North West Shelf in February 1995. Results show strong upwelling of nutrients and a phytoplankton bloom. While chlorophyll changes were similar to those estimated from satellite data in other coastal systems exposed to cyclonic conditions, the overall phytoplankton response was limited by cyclone induced sediment resuspension and the net contribution to annual primary production on the shelf was relatively small. In contrast, sediment loads exported off the shelf during Bobby were found to be more than 50 times modeled annual loads in years with little cyclone exposure and equivalent to at least 20 years of annual river‐loads to the North West Shelf.