Iceberg Poses Threat To Mariners In Southern Ocean

A large iceberg has entered shipping lanes between the Antarctic Peninsula and South America. The iceberg, named B-10A, measures 24 by 48 statute miles and could pose a hazard for mariners operating in the Southern Ocean, the National Ice Center reported. B-10A is presently located in the vicinity of Latitude 58 degrees, 36 minutes South, Longitude 57 degrees West, and is drifting southeast at approximately 7 to 9 miles per day. Smaller icebergs are breaking off B-10A as it moves into relatively warmer water. A cautionary zone has been established 165 miles in radius around the center point of B-10A. B-10, the “parent” iceberg from which B-10A formed, was once a piece of the Thwaites Ice Tongue, an extension of the Thwaites Glacier. The Thwaites Glacier flows into the Amundsen Sea about 30 miles East of Mount Murphy, Marie Byrd Land. Seaward of the glacier is a large, floating glacier tongue, part of which broke off or “calved” over a decade ago, forming B-10. Ice shelves and outlet glaciers, which move seaward on a decadal time scale, are floating extensions of a grounded ice sheet. They are composed of fresh water ice that originally fell as snow and are largely considered geographically permanent features. When an ice shelf or an outlet glacier extends far enough seaward to be affected by tides and currents, a tabular or irregular piece calves and floats away. The National Ice Center has been tracking B-10 since January, 1992. In the summer of 1995, the iceberg broke into two pieces; the larger of which became B-10A. The smaller iceberg drifted west in and along the Antarctic ice pack and eventually became too small to warrant tracking. The National Ice Center, located in Suitland, Maryland, is a tri-agency operational activity with representation from the U.S. Navy, the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Coast Guard. Its mission is to provide world-wide operational sea ice analyses and forecasts tailored to meet the requirements of U.S. national interests. The center tracks icebergs using remotely sensed data provided in part by satellites operated by NOAA and the Department of Defense. Imagery from the new Seawinds instrument aboard NASA’s QuikSCAT satellite, which uses active radar pulses, helped in identifying B-10A’s recent activity. Iceberg names are derived from the Antarctic quadrant in which they were originally sighted. The quadrants are divided counter-clockwise in the following manner: A = 0 to 90 degrees West longitude (Bellinghausen/Weddell Sea) B = 90 West to 180 (Amundsen/Eastern Ross Sea) C = 180 to 90 East (Western Ross Sea/Wilkesland) D = 90 East to 0 (Amery/Eastern Weddell Sea) When an iceberg is first sighted, the National Ice Center documents its point of origin. The letter of the quadrant, along with a sequential number, is assigned to the iceberg. For example, A-38 is the 38th iceberg the ice center has found in the Antarctica in Quadrant A.