The North Pacific: A Global-Scale Estuary

The atmospheric net flow of water from the Atlantic to the Pacific Ocean is supposed to maintain the salinity difference between the two oceans. Assuming the existence of a subsurface level of no horizontal pressure gradient in the ocean, the mean sea level in the northern Pacific must be higher than in the Arctic Ocean. This mean sea level difference is supposed to drive the observed mean flow through the Bering Strait. The estimated flow of freshwater through the Bering Strait is approximately equal to the estimated atmospheric net flow of water from the North Atlantic to the North Pacific. This justifies the formulation of a simple estuary model for the North Pacific in which the “brackish” water exits through the Bering Strait. The salinity difference between the two oceans is shown to be controlled by the topography of the Bering Strait. The estuary model gives residence times for water in the upper layer (∼1000 m thick) of approximately 1000 years and in the lower layer of approximately 4000 years.