Simulations of coastal upwelling on the Sydney continental shelf

Two-dimensional numerical simulations of the response of the coastal waters of Sydney, south-eastern Australia, to idealized upwelling-favourable wind s are presented. The spin up of the upwelling circulation is investigated, in particular the structure of the nearshore circulation. The intensity of the final upwelling state is found to be strongly linked to the activation of the return flow through the bottom boundary layer, which is also related to the strength of imposed alongshore pressure gradients. Results from a s imulation of upwelling forced by a deep-ocean alongshore-current jet also s how the final upwelling state to be weak in comparison with upwelling state s produced by the action of the local wind stress. Bottom boundary layer sh ut-down in the presence of such a forcing jet is also discussed. A simulati on of a real upwelling event was also performed and good agreement was foun d between the simulation and observations from a field experiment performed during summer 1994 in the Sydney coastal ocean.