Vol. 24., No. 11	December 23, 1998

Traveling Under Arctic Ice, Columbia Engineers Collect Unprecedented Images of Sea Floor

By Hannah Fairfield

Two Columbia engineers traveling under the Arctic ice aboard a U.S. Navy submarine have collected unprecedented high-precision images of the largely unmapped Arctic Ocean seafloor.

The expedition, which concluded this fall, featured a new civilian sonar system mounted on the hull of the nuclear-powered USS Hawkbill.

Dale Chayes and Jay Ardai, both of Columbia's Lamont-Doherty Earth Observatory in Palisades, N.Y., designed the new sonars, called Seafloor Characterization and Mapping Pods (SCAMP), and operated them during the cruise, which lasted from June 1 to Sept. 15. The engineers hailed the data collection as an overwhelming success. "It was a very aggressive effort to use a system of this complexity," said Chayes, who spent several years developing SCAMP in anticipation of the cruise. "Swath bathymetry had never been done in the arctic. Before this, maps were drawn with just sparse point soundings; now, we have data showing rugged topography, including peaks rising to within 1,000 meters of the sea surface."

SCAMP's swath mapping system measured seafloor depths across a zone that extended up to six miles on either side of the submarine as it advanced. These measurements are stitched together to create continuous, large-scale maps of the ocean floor. The swath mapping system also collected backscatter data, which illuminates seafloor textures such as lava flows. SCAMP's second sonar is a sub-bottom profiling system that mapped structures below the seafloor to approximately 100 meters.

"It is pleasing when several systems can support each other and provide an answer that an individual system could not," Ardai said.

Chayes and Ardai were part of the four-man civilian scientific crew aboard the USS Hawkbill. Other institutions represented were Earth and Space Research in Seattle, and the University of Hawaii. The scientific crew gathered data for 12 on-going research projects, mostly funded by the National Science Foundation, the Palisades Geophysical Institute and the Geological Survey of Canada.

One project may contribute to global warming research. Water temperature and salinity data collected during this mission aboard the Hawkbill is several tenths of a degree Celsius warmer than data collected from the same areas at the same time of year in previous years. "The indications for more heat than normal are there," said Ardai, who has built geophysical equipment for arctic and antarctic research for 26 years. "But it is so hard to generalize comparisons from year to year."

The research projects are part of the Scientific Ice Expedition (SCICEX), which started in 1993, when the Navy permitted unclassified research aboard its nuclear-powered submarines.

The last SCICEX cruise in this series is scheduled for 1999. SCAMP will be on board again, and though this year was a success, Chayes and Ardai are already planning improvements on the equipment in hopes of extending the maps on the ridges that cross the arctic basins.