The tropical oceans illustrate the effects of close coupling with the atmosphere on many timescales. If you ask "Why are there strong trade winds?", a meteorologist might say "That's simple, there are trade winds because the SST is cold in the east and warm in the west". But if you ask "Why is the SST cold in the east and warm in the west?", an oceanographer might say "That's simple, it's because there are trade winds". The ocean and the atmosphere are inextricably coupled together in the tropics and to understand their dynamics it is necessary to study them together.

Present-day understanding of the tropical oceans is best in the mid-basins, far from the coasts, where the currents flow primarily east or west. This occurs because the trade winds provide a relatively steady westward forcing, and because the Earth's rotation is such a strong influence that it enforces a circulation roughly along constant latitude. This picture breaks down near the coast, where the winds often come from different directions and where friction comes into play. Of course, currents can't flow into the coast, but must turn around, and the mass that they carry must flow elsewhere. We still have only a rudimentary understanding of how the great east-west currents interconnect near the coasts, and the mass and heat exchanged among the currents there has important implications for how phenomena like El Nino might be triggered or modulated.

More information:

The physics of ENSO (El-Nino/Southern Oscillation)

Decadal modulation of the ENSO cycle

Cloud feedback on air-sea coupling

Advanced Courses beyond the Physical Oceanography Core

Faculty

Meghan Cronin

Charlie Eriksen

Ed Harrison

Greg Johnson

Billy Kessler

Mike McPhaden

Dennis Moore