NSF PR 02-46 - May 23, 2002
Huge Antarctic Icebergs Break Away Near NSF Research
Two new and very large icebergs broke away from the
Ross Ice Shelf in Antarctica earlier this month in
a natural "calving" process that returned the edge
of the shelf to its pre-exploration position of the
early 1900's, researchers say.
The icebergs were designated C-18 and C-19 by the Suitland,
Md.-based National Ice Center (NIC), a joint operation
of the U.S. Navy, the National Oceanic and Atmospheric
Administration, and the U.S. Coast Guard.
Using data collected from the Defense Meteorological
Satellite Program, NIC said that C-19, the larger
of the two icebergs, is 199 kilometers (108 nautical
miles) long by 30.5 kilometers (17 nautical miles)
wide. C-18 is roughly 75.9 kilometers (41 nautical
miles) long by 7.4 kilometers (4 nautical miles) wide.
Researchers at the National Science Foundation (NSF)-funded
Antarctic Meteorological Research Center (AMRC) at
the University of Wisconsin-Madison and meteorologists
at McMurdo Station, NSF's logistics hub in Antarctica,
almost simultaneously noticed the break in the Ross
Shelf where C-19 calved.
Linda Keller of the university's department of atmospheric
and oceanic sciences noticed the crack while posting
daily images on the AMRC Web site. Both the forecasters
and the university subsequently notified the National
The AMRC makes daily composite images from weather-satellite
data available on the World Wide Web. It also monitors
icebergs and has tracked the large iceberg B-15 since
it calved in March 2000.
Douglas MacAyeal, an NSF-funded researcher at the University
of Chicago, who placed automated weather stations
and tracking devices on B-15A, a enormous fragment
of the larger iceberg, said that the satellite and
other technologies are allowing science for the first
time in history to observe the calving of large icebergs
like C-19 and B-15. The process, he noted, is part
of a natural cycle in which ice shelves grow and then
calve icebergs over geological time scales.
Researchers also noted that the developments on the
Ross Shelf are markedly different from the process
underlying the widely publicized collapse of the Larsen
B ice shelf much farther north on the Antarctic Peninsula
early this year. While still not fully understood
in terms of glaciological history, scientists believe
that the Larsen B collapse is tied to a documented
temperature increase on the Antarctic Peninsula. NIC
reported that another huge iceberg, roughly 30 nautical
miles (55.5 kilometers) long by six nautical miles
(11.1 kilometers) wide, calved in the Weddell Sea
on May 17. It was designated iceberg D-17.
Unlike B-15, which calved from a different point on
the Ross shelf, C-19 broke away relatively close to
Ross Island, where McMurdo Station is located. B-15A
and C-19 are now sitting at right angles to each other,
adjacent to Ross Island.
Although the fate of the C-19 is unknown, Charles Stearns,
emeritus professor of meteorology at the University
of Wisconsin, said the calving brings the Ross Ice
Shelf to roughly the size it was in 1911, when members
of British explorer Robert Falcon Scott's party first
mapped it. Stearns also noted that while the calving
of C-19 was fairly rapid, the fissure from which the
iceberg broke away from the shelf has been known to
scientists since the 1980's.
For updated satellite images of iceberg C-19 from AMRC,