Researchers supported by the National Science Foundation (NSF) are sailing aboard a U.S. Navy nuclear submarine in April to map the oceanic ridges and basins beneath the Arctic ice cap and study ocean currents that may have an affect on global climate.
NSF is mounting Scientific Ice Expedition (SCICEX) '99 in cooperation with the U.S. Navy and the Office of Naval Research. The exercise is the fifth in a series of annual SCICEX missions, all of which have employed some of the world's stealthiest and most maneuverable warships. "This is a capability that is not available anywhere else in the world," stressed Thomas E. Pyle, head of Arctic Sciences in NSF's Office of Polar Programs.
SCICEX '99 will be conducted aboard USS Hawkbill (SSN 666), which is able to travel almost at will under the ice, making it a unique platform for a sophisticated sonar system dubbed the Seafloor Characterization and Mapping Pods (SCAMP).
SCAMP consists of two separate, but complimentary devices. The Sidescan Swath Bathymetric Sonar (SSBS) produces an image of the sea floor on either side of the submarine. A second sonar, the High-Resolution Sub-bottom Profiler (HRSP), sends signals into the upper 200 meters of the seabed to make images of the structure of underlying sediments. "The fundamental problem that we're trying to solve is how to do high-resolution imaging of the sea floor in the Arctic in a fashion that is similar to what we do in the open ocean from surface vessels," said Dale Chayes, a senior staff associate at Columbia University's Lamont-Doherty Earth Observatory (LDEO).
Chief scientist for SCICEX '99 Margo H. Edwards, of the University of Hawaii, said SCAMP will help investigate the character of the ocean-floor in waters that ice cover previously made largely inaccessible to civilian researchers. The SCICEX team will examine the Gakkel Ridge, the slowest spreading mid-ocean ridge in the world. Although the ridges usually are sites of volcanic activity, scientists expect to find fewer eruptions there. Less volcanism may make it possible to better understand the other processes that contribute to the creation of oceanic crust. Scientists also will look for evidence of glacial scouring on the Chukchi Borderland off Alaska that could provide evidence of the extent and depth of ice cover during the last Ice Age. They also will examine the Lomonosov Ridge to obtain clues as to how the Amerasian basin, one of several basins in the Arctic, may have formed. This year's SCICEX mission includes an unusual venture into Norwegian territorial waters to study
Sensors mounted on the submarine's "sail", probes launched into the water that transmit data by wire and chemical analyses of water samples collected while underway will help determine the temperature, salinity and composition of a strong circumpolar current that flows around the boundary of the Arctic Ocean, said Tom Weingartner, a marine scientist at the University of Alaska-Fairbanks. The current transports water from the Atlantic and Pacific oceans throughout the Arctic, he noted. "Those water masses play a very important role in the present-day status of the ice pack and changes in the delivery would have an influence and effect on ice distribution," he added. Such changes could affect how much heat is reflected and absorbed by the ice pack, which could, in turn, have global implications.
Aboard Hawkbill, measurements of temperature and salinity that can be made at very closely spaced increments of time over a period of five days, would probably require at least a month to conduct on an icebreaker, he said. Such drastic differences in the duration and frequency of the sampling could dramatically affect its usefulness, he noted.
Editor: For more information, including abstracts of previous SCICEX research, see: http://www.ldeo.columbia.edu/scicex/
Materials provided by National Science Foundation. Note: Content may be edited for style and length.
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