Scientists Crack Iceberg Mystery
Date: 28-Nov-08
Country: NORWAY
Scientists Crack Iceberg Mystery Photo: Michael Kappeler/Pool
Picture
shows a fjord behind the town of Ilulissat in Greenland August 16, 2007.
Photo: Michael Kappeler/Pool
OSLO - US scientists have figured out how icebergs break off Antarctica and
Greenland, a finding that may help predict rising sea levels as the climate
warms.
Writing in Friday's edition of the journal Science, they said icebergs
formed fast when parent ice sheets spread out quickly over the sea.
"It won't help the Titanic, but a newly derived, simple law may help
scientists improve their climate models" and predict ice sheet break-up,
they said in a statement. The Titanic sank in 1912 after hitting an iceberg,
killing 1,500 people.
Ice cracking off into the ocean from Antarctica and Greenland could be the
main contributor to global sea level rises in the future. If all the ice in
Greenland and Antarctica melted, seas would rise by more than 60 meters (196
ft).
The formation rate of icebergs was less linked to factors such as ice
thickness, width of the ice flow, distance from land or waves, the
scientists said.
Ice sheets are giant frozen rivers, caused by snowfall, that slowly flow to
the sea and then break up.
In Antarctica, the Ross Ice Shelf extends 500 miles over the ocean before
the edges snap off and form icebergs. Many other ice sheets stretch just a
mile or two.
Computer models that predict how ice sheets behave in warmer weather
generally gloss over exactly how icebergs break off because researchers have
failed to understand the mechanism, known as calving.
"For iceberg calving, the important variable -- the one that accounts for
the largest portion of when the iceberg breaks -- is the rate at which ice
shelves spread," the study said.
A fast spread means cracks form throughout the shelf and make it crack up. A
slower spread means that deep cracks do not form as fast and the ice sticks
together.
"The problem of when things break is a really hard problem because there is
so much variability," lead author Richard Alley, of Pennsylvania State
University, said.
"Anyone who has dropped a coffee cup knows this. Sometimes the coffee cup
breaks and sometimes it bounces," he said of the problems of understanding
cracking.
The UN Climate Panel predicts seas will rise by 18 to 59 cm (7-23 inches)
this century because of warming stoked by human use of fossil fuels.
-- For Reuters latest environment blogs go to: blogs.reuters.com/environment/
(Editing by Catherine Bosley)
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