Newly Equipped Navy Sub Departs for 75-Day Mapping Cruise

A U.S. Navy nuclear-powered submarine has been fitted with a sophisticated new civilian sonar system that will provide scientists with unprecedented three-dimensional images of the largely unmapped seafloor beneath the Arctic Ocean.

The new sonars, know together as the Seafloor Characterization and Mapping Pods (SCAMP) have been mounted on the underside of the USS Hawkbill, which is en route to the Arctic for the Navy's fourth annual unclassified science cruise.

Two Columbia engineers were on board when the USS Hawkbill sailed June 1st from Pearl Harbor for the 75-day cruise. Dale Chayes and Jay Ardai, both of Columbia's Lamont-Doherty Earth Observatory, Palisades, N.Y., will operate the sonars and oversee acquisition of geophysical data during the cruise.

"We can now do mapping in the Arctic that has never been done before," said Mr. Chayes, who has spent several years developing SCAMP in anticipation of the cruise. "The sub can go farther and faster under the ice than any icebreakers can go through it. And because the sub is so much quieter and more stable, we can get much higher quality sonar data that will reveal a picture of the Arctic seafloor that we have never had before."

SCAMP is made of two sonar mapping systems, designed to take advantage of the submarineÕs unique characteristics. One is a swath mapping system, which measures seafloor depths across a zone extending up to about six miles on either side of the advancing submarine. These measurements can be stitched together to create continuous, large-scale maps of the ocean floor. The swath mapping system also collects backscatter data, which illuminates seafloor textures such as scarps and lava flows. SCAMP's other sonar is a sub-bottom profiling system that will profile structures down to about 100 meters below the seafloor.

Lamont geophysicists Bernard Coakley and James Cochran will use SCAMP data to obtain 3-D images of seafloor features, such as the Gakkel Ridge, a spreading center between North American and Eurasian tectonic plates where new seafloor is created. "Data collected will help us to understand how oceanic crust is formed at spreading centers and the processes by which magma is brought to the surface," Dr. Cochran said.

The SCAMP system attached to the sub will allow scientists to "collect data like mowing the lawn," said Dr. Coakley, who took part in the first two SCICEX (Scientific Ice Expedition) cruises in 1993 and 1995, the first time the Navy permitted unclassified research aboard its nuclear-powered submarines. Subsequent SCICEX cruises took place in 1995, 1996 and 1997, and another is planned for 1999.

The Hawkbill will also collect water samples, which will be used to study Arctic Ocean circulation by two Lamont geochemists, William Smethie and Peter Schlosser. The Arctic Ocean plays an important, but still poorly understood, role in regulating the EarthÕs climate. Dr. Smethie uses chlorofluorocarbons and Dr. Schlosser uses isotopes of hydrogen and helium to trace the direction and speed of waters circulating through the ocean.

Aside from Mssrs. Chayes and Ardai, three other researchers from the University of Hawaii, Oregon State University, and Earth and Space Research, a private non-profit research agency in Seattle, will be aboard the Hawkbill.

The systems were funded by the National Science Foundation's Arctic Sciences Section with assistance from the Palisades Geophysical Institute and the Geological Survey of Canada. Research by Drs. Coakley, Cochran, Schlosser and Smethie is also funded by NSF. Funding for participation of Lamont scientists and engineers in the SCICEX program comes from the U.S. NavyÕs Office of Naval Research and NSF's Office of Polar Programs, the Palisades Geophysical Institute, Inc., and the Geological Survey of Canada.

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