Enormous Iceberg May Be In Its Death Throes

TERRADAILY

Smaller icebergs of varying sizes float in a zone between iceberg B-15A and a smaller, but still extremely large berg designated C-16. The collision zone between the two bergs is marked by narrow canyons and wide, ice-choked bays as well as by areas such as those in the center of the picture, where the edges of the bergs have been forced up into peaks by collisions. Photo by Peter West for National Science Foundation. Raw Desktop image

Washington - Feb 14, 2002
For perhaps the last time, a researcher has visited iceberg B-15A, an enormous fragment of ice that broke away from Antarctica's Ross Ice Shelf in March 2000.

During a one-hour visit on Jan. 29 (New Zealand time), Douglas MacAyeal of the University of Chicago upgraded the software of an automated weather station on the enormous piece of ice that helps track the iceberg's position and reports on the microclimate of the ice surface.

Supported by the U.S. Antarctic Program, MacAyeal and other researchers placed weather stations on the iceberg a year ago. This year, MacAyeal flew twice to B-15A on U.S. Coast Guard helicopters to update the software that allows the weather stations to transmit data and to adjust the sensors that measure wind speed.

MacAyeal said that collisions between B-15A and a much smaller, though still impressive, iceberg, dubbed C-16, have begun the process of breaking up the bigger berg. He suspects B15A will crumble into pieces and drift northward away from McMurdo Sound when summer returns to Antarctica, almost a year from now.

"B-15A is ripe" for a breakup, he said. "But it's a 'wait and-see' sort of thing." During the flights to and from the iceberg from McMurdo Station, the main NSF research station in Antarctica, MacAyeal pointed out enormous cracks developing on the berg's surface. He also noted areas where the two icebergs have ground together, generating as much as 4,000 pounds per square inch of pressure.

A zone between the two bergs features both narrow ice canyons 30 meters (100 feet) deep and spacious bays, in which icebergs that ordinarily would be thought of as colossal seem insignificant in comparison with their larger neighbors. MacAyeal noted that few human eyes have seen such phenomena.

The collisions, he said, accelerate the breakup of both bergs and the movement of the remaining fragments out to sea.

By observing B-15A and C-16, "we've learned that collisions of this nature provide a force that helps propel an iceberg on its track," MacAyeal said.

He added that it is possible that scientists may be observing for the first time a cycle in which portions of the Ross Ice Shelf break off and fall into the sea as giant icebergs. The National Ice Center, in Suitland, Md., reported that a new iceberg, dubbed C-17, broke away from the Ross Shelf on Feb. 7. C17, which broke away from the Matusevich Glacier, is estimated to be 58 square miles in area, or roughly the size of Manhattan Island.

Meanwhile, An iceberg newly calved from the Matusevich Glacier Tongue in Antarctica has been discovered by the National Ice Center in Suitland, Md. The Matusevich Glacial Tongue is a large extension of the Matusevich Glacier from the Antarctic mainland into the northwestern Ross Sea.

This new iceberg, named C-17, is roughly 11 nautical miles long and 4 nautical miles wide, and covers an area of approximately 58.24 square statute miles. An analyst at the center spotted the new berg while performing a weekly analysis of the Ross Sea. The berg was located with a satellite image from the Defense Meteorological Satellite Program's Operational Line Scan Visible sensor.

ICEBERGS

Classic Tabular Iceberg Sheds From West Antarctic Glacier

Pasadena - Nov 18, 2001
To the surprise of scientists, a large iceberg has broken off the Pine Island Glacier in West Antarctica well in advance of predictions. The new iceberg detached from the glacier when a crack, which initially formed in mid-2000, spread rapidly until it reached the breaking point. The iceberg's birth was captured in a series of images taken by NASA's Multi-angle Imaging SpectroRadiometer.

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