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SATELLITE DATA REVEAL NEW VIEW OF 

 OCEAN BOTTOM 



Scientists at U.C. San Diego's Scripps Institution of Oceanography (SIO) and the 

 National Oceanic and Atmospheric Administration (NOAA) have used satellite 

 measurements to develop the most detailed picture to date of the global sea floor. 

 The computerized image of the sea floor opens new doors to imderwater 

 exploration, including identifying previously unknown volcanoes, studying the 

 tectonic history of the oceans, and searching for untapped petrolevun reserves. 



David Sandwell, a professor at SIO's Institute of Geophysics and Planetary Physics, 

 and Walter Smith of NOAA created the new map by combining newly declassified 

 measurements from the Navy's Geosat satellite with data collected by a European 

 satellite, ERS-1. Scientists have been attempting to map the Earth's underwater 

 terrain using shipboard sonar since the 1920s; however, they were only able to chart 

 about five percent of the global seafloor from ships. Sandwell estimates it would 

 take approximately 125 years to chart the ocean basins using the latest sonar tools. 



Fortunately, such a costly undertaking is no longer necessary because scientists have 

 devised a new way to explore the ocean bottom from space. Although satellite 

 sensors are incapable of imaging the seafloor directly, scientists can use satellites to 

 measure the height of the sea surface to fractions of an inch. The gravitational 

 attraction generated by geological structures such as mountains and valleys on the 

 seafloor cause broad bumps and dips on the sea surface. By analyzing the surface 

 gravity fields such structures create, Sandwell and Smith were able to infer what the 

 topography of the sea floor looks like. This analysis provides us with the first 

 overall view of 70 percent of the Earth's surface in very fine detail. 



Sophisticated satellite data on the sea surface have only recently been made 

 available to oceanographers. The Geosat data began to be declassified in response to 

 requests from scientists as part of the activities of the Environmental Task Force 

 (ETF). ETF and its follow-on effort, MEDEA, reviewed the feasibility of declassifying 

 intelligence and defense data and systems for use by scientists to address serious 

 global environmental problems. SIO scientists look forward to continuing to work 

 with the national security community on this effort. 



SCRIPPS INSTITUTION OF OCEANOGRAPHY 

 UNIVERSITY OF CALIFORNIA, SAN DIEGO 



