Multibeam Bathymetry Mapping for U.S. UNCLOS Concerns: A Gold Mine for Marine Geology

• Main Authors: Armstrong, Andy, Gardner, James V., Mayer, Larry A.
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2007
• Subjects: Law of the Sea; Oceanography and Atmospheric Sciences and Meteorology; Arctic; Arctic Ocean; Bering Sea; Gulf of Alaska; Bowers; Healy Seamount; Barrow; Alaska
• Online Access: https://scholars.unh.edu/ccom/586; http://abstractsearch.agu.org/meetings/2007/FM/OS53A-0965.html

Since 2003, the University of New Hampshire's Center for Coastal and Ocean Mapping�Joint Hydrographic Center has conducted mapping of several U.S. continental margins in areas where a potential exists for an extended continental shelf as defined under Article 76 of the United Nations Convention on the Law of the Sea. UNH was directed by Congress, through funding to NOAA, to map the bathymetry in areas in the Arctic Ocean, Bering Sea, Gulf of Alaska, Atlantic, Gulf of Mexico, Philippine Sea, and slopes of Kingman Reef and Palmyra Atoll. These new data can be used to accurately locate the 2500-m isobath and to determine the location of the maximum change in gradient at the base of the continental slopes. To achieve these objectives, the area between ~1000 m and ~5000 m isobaths are mapped. The program has mapped >900,000 km2 as of September 2007. The bathymetry data are collected with multibeam echosounders navigated with inertial-aided DGPS and are fully motion compensated. An integral part of the data collection is measurements of the sound-speed profile in the water column to correct for refraction. The data are fully processed at sea. Most cruises also collect 3.5-kHz high-resolution profiles and some have included gravity measurements. All processed bathymetry and associated acoustic backscatter data are immediately available one the web and the raw multibeam datagrams and processed gravity data are archived at NOAA/NGDC. The new data provide a wealth of new information on the geomorphology of the continental margins. The mapping discovered many new features on the U.S. margins, as well as better defined features known to exist but either poorly mapped or mapped with obsolete mapping technology. New features discovered during the surveys include an undiscovered seamount, christened Healy Seamount and a series of huge sediment ridges striking normal to the Barrow margin in the Arctic Ocean; a series of plateaus and ridges north of Bowers Ridge in the Bering Sea; deep-sea channels incising two submarine fans ...