On the total geostrophic circulation of the Pacific Ocean: flow patterns, tracers, and transports

The large-scale circulation of the Pacific Ocean consists of two great anticyclonic gyres that contract poleward at increasing depth, two high-latitude cyclonic gyres, two westward hows along 10 degrees to 15 degrees north and south that are found from the surface to abyssal depths, and an eastward flow that takes place just north of the equator at the surface and at about 500m, but lies along the equator at all other depths. This pattern is roughly symmetric about the equator except for the northward flow across the equator in the west and the southward how in the east. As no water denser than about 26.8 in sigma(0) is formed in the North Pacific, the denser waters of the North Pacific are dominated by the inflow from the South Pacific. Salinity and oxygen in the deeper water are higher in the South Pacific and the nutrients are lower. These characteristics define recognizable paths as they move northward across the equator in the west and circulate within the North Pacific. Return flow is seen across the equator in the east. Part of it turns westward and then southward with the southward limb of the extended cyclonic gyre, and part continues southward along the eastern boundary and through the Drake Passage. The important differences from earlier studies are that the equatorial crossings and the deep paths of flow are defined, and that there are strong cyclonic gyres in the tropics on either side of the equator. (C) 1997 Elsevier Science Ltd. All rights reserved.