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Tsunami Broke Antarctic Ice Shelf
By Kieran Mulvaney | Tue Aug 9, 2011 07:03 AM ET
http://news.discovery.com/earth/japan-tsunami-broke-antarctic-ice-shelf-110809.html
Anyone who saw any of the footage of the
devastation wreaked upon Japan by the March 11
earthquake and tsunami - as most of us have done -
can have no doubt about the overwhelming power they
contained and unleashed. Now researchers have found
that the force of the tsunami was so great that it
was able to break several pieces of ice, totaling
more than twice the size of Manhattan, from an
Antarctic ice shelf 8,000 miles from the quake's
epicenter.
Writing in the online version of the Journal of
Glaciology, Kelly Brunt of NASA's Goddard Space
Flight Center and colleagues describe how
researchers have long suspected that repeated
flexing of an ice shelf as a result of forces from
a seismic event could lead to the calving of
icebergs, but there had been no observations to
confirm the theory. And so, shortly after the March
11 earthquake struck, Brunt and colleagues
calculated the likely path the tsunami would follow
throughout the Pacific basin in anticipation of
such an event occurring.
BLOG: Behold, The Floating Ice Island
They focused their attention on the Sulzberger Ice
Shelf, on the northeast coast of the Ross Sea south
of New Zealand. Remarkably, approximately 18 hours
after the tsunami struck Japan, a gap in the clouds
above the ice shelf revealed the presence of one
large iceberg that had broken off. Recourse to
cloud-penetrating radar satellites uncovered the
existence of another large iceberg with several
smaller ones also breaking away behind them. Brunt
and colleagues estimate that by the time the
tsunami reached the Antarctic coast, waves were
only a foot or so high, but even so, the scientists
say the consistency of the swell was enough to
cause the icebergs to fracture from an outcrop of
ice that had apparently stood unbroken since at
least 1965, when it was captured by aerial
photographs.
"In the past we've had calving events where we've
looked for the source. It's a reverse scenario – we
see a calving and we go looking for a source,"
Brunt said in a press release. "We knew right away
this was one of the biggest events in recent
history – we knew there would be enough swell. And
this time we had a source."
Images by the European Space Agency/Envisat.
Video by NASA/Goddard
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