|Gravity Field Atlas of the S. Ocean
|This Gravity Field Atlas of the Southern Ocean from GEOSAT is MGG Report 7. In many
areas of the global ocean, the depth of the seafloor is not well known because survey
lines by ships are hundreds of kilometers apart. Satellites carrying radar altimeters
have measured the shape of the ocean along tracks only 3-4 km apart, and from these
data we can make very accuratore (+/-3mGal) and high resolution (15km) maps of the
marine gravity field. The gravity field mimics the seafloor topography in the 15-160
km wavelength band if sediment cover on the ocean floor is thin. Long-wavelength (greater
than 160 km) topography is isostatically compensated and is not correlated with the
gravity field. In addition, the satellite gravity field and the available depth measurements
were used to determine the correlation between gravity and the seafloor topography.
By applying this correlation to the gravity field we predict seafloor topography in
the 15-160 km wavelength band. This topography is combined with a long-wavelength
component estimated directly from ship depth measurements. The result reveals many
new features and is within +/- 100m of actual depths in many cases. The Predicted
Seafloor Topography derived from the depths estimated from Satellite Altimetry in
combination with measured trackline bathymetry is an inferred data set and is not
true bathymetry. It is, however, the best estimate of seafloor topography available
resulting from satellite gravity data and actual ship depth measurements. These data
are intended for scientific research and should not be used for navigational purposes.
Additional software is required in order to manipulate the data or produce your own
graphic images. Poster and CD-ROM products are available for both gravity anomaly
and estimated seafloor topography of several regions. Please refer to URL http://www.ngdc.noaa.gov/mgg/fliers/92mgg04.html
more information, and to download sample images.