TOPEX/Poseidon: Perspectives on an Ocean Planet

Global Ocean Circulation

Surface circulation carries the warm upper waters poleward from the tropics. Heat is disbursed along the way from the waters to the atmosphere. At the poles, the water is further cooled during winter, and sinks to the deep ocean. This is especially true in the North Atlantic and along Antarctica. Deep ocean water gradually returns to the surface nearly everywhere in the ocean. Once at the surface it is carried back to the tropics, and the cycle begins again. The more efficient the cycle, the more heat is transferred, and the warmer the climate.

Due to the rotation of the earth, currents are deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This effect is known as the "Coriolis force." The deflection leads to highs and lows of sea level directly proportional to the speed of the surface currents. The changes in sea level due to currents are the ocean topography that is observed by TOPEX/Poseidon.

Observations of ocean topography and a knowledge of the Coriolis force permit scientists to map ocean currents using data from the satellite. Every ten days TOPEX/Poseidon produces maps of the currents everywhere in the ocean.

Variations in the ocean’s circulation can lead to variations in heat transport and to variations in weather patterns. One important variation in the circulation is the change in the equatorial circulation known as El Nino which occurs with an irregular period of two to five years. The most recent El Ninos have been observed with unprecedented accuracy by TOPEX/Poseidon.