Page 62: of Maritime Reporter Magazine (October 1997)

TECHNOLOGY UPDATE

Scientists Develop New Map Of The World's Sea Floors

Scientists have used gravity data from satellites in addition to depth soundings from ships to produce a more defined, high-resolution map of the world's ocean floors, the U.S.

National Oceanic and Atmospheric

Administration (NOAA) announced.

The new map provides estimations of the ocean depths from gravity data from satel- lites.

An older version of the map, produced in 1995, was based on gravity data, but did not provide estimations of ocean depths.

Scientists Walter H.F. Smith of NOAA's

National Oceanographic Data Center and

David T. Sandwell of the Scripps Institution of Oceanography, University of California,

San Diego, report on their project in the

September 26 issue of Science magazine.

Filling In The Gaps

Conventional sea floor mapping using echo sounding data from ships has been difficult because of the large gaps between surveys in remote areas. "There are places as large as the State of

Oklahoma where no soundings are avail- able," said Mr. Smith. "Traditionally, bathy- metric contours are drawn by hand, so that human intuition (or prejudice) fills the gaps in coverage," both scientists wrote in Science. "Recent developments allow a new approach to this problem."

Mr. Smith and Mr. Sandwell used gravity data from satellites to estimate depths in unsurveyed areas, thus filling the gaps in the map in an objective and high-resolution man- ner.

The new topography reveals all of the intermediate and large-scale structures of the ocean basins, including new mountain ranges such as the

Foundation Seamounts in the South

Pacific.

These were not found by conventional mapping but were revealed by the satel- lite gravity data.

The pair of scientists showed that unchart- ed seamounts are a significant source of topo- graphic variation, and information from satellite gravity can reduce the error in esti- mated topographic variation by more than half.

Knowledge of sea floor topography is vital for understanding physical oceanography, marine biology, chemistry and geology.

Topography influences currents, tides, and mixing and upwelling of nutrient-rich water.

The new topographic features portrayed by

Mr. Smith and Mr. Sandwell reveal new fish habitats, and should influence computer sim- ulations of ocean circulation.

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Engine Extend Cooperation

Wartsila NSD Corp. and

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Maritime Reporter/Engineering News