Gravity Recovery and Climate Experiment
GRACE, twin satellites launched in March 2002, are making detailed
measurements of Earth's gravity field which will lead to discoveries
about gravity and Earth's natural systems. These discoveries could have
far-reaching benefits to society and the world's population.
Ocean currents transport mass and heat between different regions of the
Earth. Knowledge of these currents is therefore vitally important for
Earth climate sciences. Some of the more familiar currents include the
Gulf Stream off the eastern seaboard of the USA, the Kuroshio Current
in the western Pacific off the coast of Japan; the Antarctic
Circumpolar Current (ACC), which is the only current to travel through
all major ocean basins; and the Equatorial Currents.
Historically, knowledge of these currents has
come from measurements from very limited number of current meters or
drifter buoys (which measure the current directly at selected points in
the oceans), or indirectly from the knowledge of slopes of the dynamic
ocean topography. The dynamic ocean topography, and thus the currents,
can be computed in two ways: 1) from measurements through the ocean
depth of temperature and salinity, using instruments dropped from ships
or from moored buoys, or 2) the difference between sea surface height
measured by satellite altimeters and a geoid model from GRACE. This independent knowledge of absolute surface currents from altimetry
and GRACE can now be used in combination with the temperature and
salintiy profiles to extract the currents as a function of depth. This
in turn will improve our knowledge of mass and heat transported by
these current systems.
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