Dynamic Topography of Earth's Oceans

Ocean Topography is a measure of sea level relative to Earth's geoid, a surface on which the gravity field is uniform. Oceanographers use ocean topography maps to calculate the speed and direction of ocean currents in the same way meteorologists use maps of atmospheric pressure to calculate the speed and direction of winds. TOPEX/Poseidon is the first space mission that allows scientists to map ocean topography with sufficient accuracy to study the large-scale current systems of the world's oceans.

The total relief of ocean topography shown in this image is about 2 meters. The color scale corresponds to the grades of the relief in centimeters. The vertical scale is greatly exaggerated to illustrate the three-dimensional perspective of the topography. In this image, the maximum sea level (shown in white) is located in the western Pacific Ocean and the minimum sea level (indicated by magenta and dark blue) is shown around Antarctica. In the northern hemisphere, ocean currents flow clockwise around the highs of ocean topography and counterclockwise around the lows; this process is reversed in the southern hemisphere. These highs and lows are the oceanic counterparts of atmospheric circulation systems. While the basic structure of these ocean systems is constant, the details of the systems are constantly changing.

Although this image was constructed from only 10 days of TOPEX/Poseidon data (October 3 to October 12, 1992), it reveals most of the current systems that have been identified by shipboard observations collected over the last 100 years. For instance, major current systems such as Kuroshio (the current south of Japan), the Gulf Stream and the Antarctic Circumpolar Current, among others, are clearly visible.

The ocean topography data used in this image were calculated by scientists at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center. The image was produced by the Jet Propulsion Laboratory (JPL) Oceanography Group.

NASA/JPL/Caltech
JPL Identification #: P-42106