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Ross Ice Shelf Breaks, As ExpectedBig Berg Loosed | |||
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The new iceberg is partially obscured by cloud on the first satellite
image that shows it. If the iceberg is all one piece, it is about as long
as the current B-15-A, roughly 200 km (about 125 miles) long. Emeritus Professor Charles Stearns is Principal Investigator for the
AMRC, and has studied and visited the continent for decades. He noted,
That crack has been there about as long as people have been going
to Antarctica. In 1987, I saw it from an icebreaker. He explained
that the edge of the ice moves down from the high Antarctic plateau covering
most of the continent at the rate of a kilometer a year and is fed by
glaciers and ice streams. The ice is 2000 to 4000 meters thick on the
plateau. It slowly moves down to the ice shelves, at the edges of the
continent, where it gradually sloughs off, or calves, in the form of icebergs.
The chunk now calving from the Ross Ice Shelf has been moving for 30
years, Stearns noted. He added, Ice flows down hill, feeding the
ice shelf. It would pile up if it did not break off. This latest
calving brings the Ross Ice Shelf to the size it was in about 1911, when
Scott's team first mapped it.
Since the current crop of calving events (icebergs being born are called
calvings) began in March 2000, Antarctic researchers have worried about
possible impacts on shipping in the southern oceans. The concern continues
with one more super-size iceberg broken free.
Keller notified the National Ice Center, which announces new icebergs,
of her discovery. They have named the new iceberg C-19.
When the AMRC receives reasonably clear images of the icebergs, they
are posted on the Web
site.
A technical paper on iceberg calvings is available in Polar Geography,
1999, No. 3, by M. Lazzara, K. Jezek, T. Scambos, D. MacAyeal and C. van
der Veen.
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