The interaction of southwest monsoon upwelling, advection and primary production in the northwest Arabian Sea

A biological model comprising phytoplankton, Zooplankton, detritus, and nitrogen pools has been coupled to a 3-layer reduced-gravity ocean circulation model of the Arabian Sea through the vertical mixing and horizontal transport fields. Coupled biophysical interactions during the southwest monsoon have been investigated using experiments with progressively more physical forcing: (1) initial-value biological calculations with no forcing; (2) upwelling simulations for the southwest monsoon that incorporate vertical forcing only; and (3) coupled physical-biological model experiments that use both upwelling and horizontal advection, and are forced by monthly varying climatological wind stresses and density profiles for the Arabian Sea. The initial-value and upwelling experiments indicate the roles of grazing pressure and remineralization of detritus when physical forcing is present. The coupled model experiments demonstrate the importance of coastal upwelling and offshore advection in determining patterns of total nitrogen in surface waters, both near the coast and offshore. Offshore jets are significant as sources of both transported nutrients and biomass in open waters far from coastal upwelling areas.