Chapter 4.3 The tropical ocean circulation

Publisher Summary This chapter highlights the tropical ocean circulation. It describes the observations and some modeling results relating to the main flows near the equator and their water mass sources, in the Pacific, Atlantic and Indian Ocean. The presentation varies for each ocean, since the issues and available data vary among the three basins. The Indian Ocean is qualitatively different from the other two. The comparison between the three equatorial oceans seems to confirm that the qualitative resemblance between current systems in the Pacific and Atlantic covers a wide variety of phenomena. Both have south equatorial current (SEC), equatorial undercurrent (EUC), and north equatorial counter current (NECC) with an annual cycle of similar phase, though the EUC display some marked quantitative differences. In addition, the Atlantic northern equatorial undercurrent (NEUC) and southern equatorial undercurrent (SEUC) seem to be somewhat similar to the northern subsurface counter current (NSCC) and southern subsurface counter current (SSCC) in the Pacific. One major difference between the Atlantic and the other two oceans is that the entire equatorial Atlantic circulation from the surface to the North Atlantic Deep Water outflow is part of an overturning cell, which transports large amounts of heat northward across the equator. In the Pacific and Indian Oceans, overturning cells are confined to the thermocline with weaker deep cells below.