NASA data: Greenland, Antarctic ice melt worsening
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Oct 20, 2009, 2:08:35 AM10/20/09
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NASA data: Greenland, Antarctic ice melt worsening
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Yahoo! Bookmarks Print By SETH BORENSTEIN, AP Science Writer Seth
Borenstein, Ap
Science Writer – Wed Sep 23, 1:01 pm ET
WASHINGTON – New satellite information shows that ice sheets in
Greenland and
western Antarctica continue to shrink faster than scientists thought
and in some
places are already in runaway melt mode.
British scientists for the first time calculated changes in the height
of the
vulnerable but massive ice sheets and found them especially worse at
their
edges. That's where warmer water eats away from below. In some parts
of
Antarctica, ice sheets have been losing 30 feet a year in thickness
since 2003,
according to a paper published online Thursday in the journal Nature.
Some of those areas are about a mile thick, so they've still got
plenty of ice
to burn through. But the drop in thickness is speeding up. In parts of
Antarctica, the yearly rate of thinning from 2003 to 2007 is 50
percent higher
than it was from 1995 to 2003.
These new measurements, based on 50 million laser readings from a NASA
satellite, confirm what some of the more pessimistic scientists
thought: The
melting along the crucial edges of the two major ice sheets is
accelerating and
is in a self-feeding loop. The more the ice melts, the more water
surrounds and
eats away at the remaining ice.
"To some extent it's a runaway effect. The question is how far will it
run?"
said the study's lead author, Hamish Pritchard of the British
Antarctic Survey.
"It's more widespread than we previously thought."
The study doesn't answer the crucial question of how much this
worsening melt
will add to projections of sea level rise from man-made global
warming. Some
scientists have previously estimated that steady melting of the two
ice sheets
will add about 3 feet, maybe more, to sea levels by the end of the
century. But
the ice sheets are so big it would probably take hundreds of years for
them to
completely disappear.
As scientists watch ice shelves retreat or just plain collapse, some
thought the
problem could slow or be temporary. The latest measurements eliminate
"the most
optimistic view," said Penn State University professor Richard Alley,
who wasn't
part of the study.
The research found that 81 of the 111 Greenland glaciers surveyed are
thinning
at an accelerating, self-feeding pace.
The key problem is not heat in the air, but the water near the ice
sheets,
Pritchard said. The water is not just warmer but its circulation is
also adding
to the melt.
"It is alarming," said Jason Box of Ohio State University, who also
wasn't part
of the study.
Worsening data, including this report, keep proving "that we're
underestimating"
how sensitive the ice sheets are to changes, he said.
___
On the Net
Nature: http://www.nature.com/
Buzz up!32 votes Send
Email IM Share
Delicious Digg Facebook Fark Newsvine Reddit StumbleUpon Technorati
Yahoo! Bookmarks Print By SETH BORENSTEIN, AP Science Writer Seth
Borenstein, Ap
Science Writer – Wed Sep 23, 1:01 pm ET
WASHINGTON – New satellite information shows that ice sheets in
Greenland and
western Antarctica continue to shrink faster than scientists thought
and in some
places are already in runaway melt mode.
British scientists for the first time calculated changes in the height
of the
vulnerable but massive ice sheets and found them especially worse at
their
edges. That's where warmer water eats away from below. In some parts
of
Antarctica, ice sheets have been losing 30 feet a year in thickness
since 2003,
according to a paper published online Thursday in the journal Nature.
Some of those areas are about a mile thick, so they've still got
plenty of ice
to burn through. But the drop in thickness is speeding up. In parts of
Antarctica, the yearly rate of thinning from 2003 to 2007 is 50
percent higher
than it was from 1995 to 2003.
These new measurements, based on 50 million laser readings from a NASA
satellite, confirm what some of the more pessimistic scientists
thought: The
melting along the crucial edges of the two major ice sheets is
accelerating and
is in a self-feeding loop. The more the ice melts, the more water
surrounds and
eats away at the remaining ice.
"To some extent it's a runaway effect. The question is how far will it
run?"
said the study's lead author, Hamish Pritchard of the British
Antarctic Survey.
"It's more widespread than we previously thought."
The study doesn't answer the crucial question of how much this
worsening melt
will add to projections of sea level rise from man-made global
warming. Some
scientists have previously estimated that steady melting of the two
ice sheets
will add about 3 feet, maybe more, to sea levels by the end of the
century. But
the ice sheets are so big it would probably take hundreds of years for
them to
completely disappear.
As scientists watch ice shelves retreat or just plain collapse, some
thought the
problem could slow or be temporary. The latest measurements eliminate
"the most
optimistic view," said Penn State University professor Richard Alley,
who wasn't
part of the study.
The research found that 81 of the 111 Greenland glaciers surveyed are
thinning
at an accelerating, self-feeding pace.
The key problem is not heat in the air, but the water near the ice
sheets,
Pritchard said. The water is not just warmer but its circulation is
also adding
to the melt.
"It is alarming," said Jason Box of Ohio State University, who also
wasn't part
of the study.
Worsening data, including this report, keep proving "that we're
underestimating"
how sensitive the ice sheets are to changes, he said.
___
On the Net
Nature: http://www.nature.com/
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