July 01, 1994
The seas of Earth are in constant motion. Large systems
of highs and lows (liquid hills and valleys) develop in the
oceans' surface as a result of ocean currents. These highs
and lows are permanent features of ocean circulation; their
existence and basic structure do not change, but the details
of these systems are constantly changing. Scientists measure
these changes by defining the oceans' dynamic (changing)
topography as a measure of sea level relative to Earth's
geoid, a surface on which Eaarth's gravity field is uniform.
With TOPEX/Poseidon data, oceanographers monitor ocean
circulation similar to how meteorologists have used
atmospheric pressure maps to predict weather for decades.
In this image, ocean currents are shown by white arrows.
The longer the arrow, the greater the speed of the current.
Speeds greater than 10 centimeters per second are
represented by thick arrows.
In the northern hemisphere, ocean current flow clockwise
around highs in ocean topography and counterclockwise around
the lows. This process is reversed in the southern
JPL Identification #: P-44076
Source: Jet Propulsion Laboratory
Return to News Archive