Abstract A general circulation model (GCM) of the ocean is used to study the effects of changes in the monsoon winds of present day and 9000 yr B.P. on the upwelling in the Arabian Sea. The vertical transport from the ocean GCM is used as a measure of upwelling strength to assess the relative abundance of Globigerina bulloides at present and 9000 yr B.P., during the climatic optimum. The high abundance of G. bulloides at 9000 yr B.P. is probably a result of a doubling of the vertical transport at that time.