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Escalating ice loss in Antarctica
Sheets melting in an area once thought to be unaffected by global
warming
By Marc Kaufman
The Washington Post
updated 3:18 a.m. ET, Mon., Jan. 14, 2008
WASHINGTON - Climatic changes appear to be destabilizing vast ice
sheets of western Antarctica that had previously seemed relatively
protected from global warming, researchers reported yesterday, raising
the prospect of faster sea-level rise than current estimates.
While the overall loss is a tiny fraction of the miles-deep ice that
covers much of Antarctica, scientists said the new finding is
important because the continent holds about 90 percent of Earth's ice,
and until now, large-scale ice loss there had been limited to the
peninsula that juts out toward the tip of South America. In addition,
researchers found that the rate of ice loss in the affected areas has
accelerated over the past 10 years -- as it has on most glaciers and
ice sheets around the world.
"Without doubt, Antarctica as a whole is now losing ice yearly, and
each year it's losing more," said Eric Rignot, lead author of a paper
published online in the journal Nature Geoscience.
The Antarctic ice sheet is shrinking despite land temperatures for the
continent remaining essentially unchanged, except for the fast-warming
peninsula.
The cause, Rignot said, may be changes in the flow of the warmer water
of the Antarctic Circumpolar Current that circles much of the
continent. Because of changed wind patterns and less-well-understood
dynamics of the submerged current, its water is coming closer to land
in some sectors and melting the edges of glaciers deep underwater.
"Something must be changing the ocean to trigger such changes," said
Rignot, a senior scientist with NASA's Jet Propulsion Laboratory. "We
believe it is related to global climate forcing."
Rignot said the tonnage of yearly ice loss in Antarctica is
approaching that of Greenland, where ice sheets are known to be
melting rapidly in some parts and where ancient glaciers have been in
retreat. He said the change in Antarctica could become considerably
more dramatic because the continent's western shelf, an expanse of ice
and snow roughly the size of Texas, is largely below sea level and has
broad and flat expanses of ice that could move quickly. Much of
Greenland's ice flows through relatively narrow valleys in mountainous
terrain, which slows its motion.
'Frightening' possibility
The new finding comes days after the head of the Intergovernmental
Panel on Climate Change said the group's next report should look at
the "frightening" possibility that ice sheets in Greenland and
Antarctica could melt rapidly at the same time.
"Both Greenland and the West Antarctic ice sheet are huge bodies of
ice and snow, which are sitting on land," said Rajendra Pachauri,
chief of the IPCC, the United Nations' scientific advisory group. "If,
through a process of melting, they collapse and are submerged in the
sea, then we really are talking about sea-level rises of several
meters." (A meter is about a yard.) Last year, the IPCC tentatively
estimated that sea levels would rise by eight inches to two feet by
the end of the century, assuming no melting in West Antarctica.
The new Antarctic ice findings are based on mapping of 85 percent of
the continent over the past decade using radar data from European,
Japanese and Canadian weather satellites. Previous studies had
detected the beginning of ice loss in West Antarctica and substantial
loss along the peninsula, but the current research found significantly
greater changes.
Rignot and his team found that East Antarctica, which holds a majority
of the continent's ice, has not experienced the same kind of loss --
probably because most of the ice sits atop land rather than below sea
level, as in the west. In several coastal areas of East Antarctica,
however, small but similar losses have been detected, he said.
In all, snowfall and ice loss in East Antarctica have about equaled
out over the past 10 years, leaving that part of the continent
unchanged in terms of total ice. But in West Antarctica, the ice loss
has increased by 59 percent over the past decade to about 132 billion
metric tons a year, while the yearly loss along the peninsula has
increased by 140 percent to 60 billion metric tons. Because the ice
being lost is generally near the bottom of glaciers, the glacier moves
faster into the water and thins further, as a result. Rignot said
there has been evidence of ice loss going back as far as 40 years.
The new findings come as the Arctic is losing ice at a dramatic rate
and glaciers are in retreat across the planet. At a recent annual
meeting of the American Geophysical Union, Ohio State University
professor Lonnie Thompson delivered a keynote lecture that described a
significant speed-up in the melting of high-altitude glaciers in
tropical regions, including Peru, Tibet and Mount Kilimanjaro in
Kenya.
Thompson, who has studied the Quelccaya glacier in the Peruvian Andes
for 30 years, said that for the first half of that period, it
retreated on average 20 feet per year. For the past 15 years, he said,
it has retreated an average of nearly 200 feet per year.
"The information from Antarctica is consistent with what we are seeing
in all other areas with glaciers -- a melting or retreat that is
occurring faster than predicted," he said. "Glaciers, and especially
the high-elevation tropical glaciers, are a real canary in the coal
mine. They're telling us that major climatic changes are occurring."
While the phenomenon of ice loss worldwide is well documented, the
dynamics in the Antarctic are probably the least understood. Glaciers
and ice sheets are sometimes miles deep, and researchers do not know
what might be happening at the bottom of the ice -- but it clearly is
being lost along the peninsula and West Antarctic coast.
Rignot theorizes that the warmer water of the Antarctic Circumpolar
Current is the cause. Douglas Martinson, a senior research scientist
fellow at the Lamont-Doherty Earth Observatory of Columbia University,
has studied the issue and agrees.
Martinson said the current, which flows about 200 yards below the
frigid surface water, began to warm significantly in the 1980s, and
that warming in turn caused wind patterns to change in ways that
ultimately brought more warm water to shore. The result has been an
increased erosion of the glaciers and ice sheets.
Martinson said researchers do not have enough data to say for certain
that the process was set in motion by global warming, but "that is
clearly the most logical answer."
Pachauri, the IPCC's chief of climate science, will visit Antarctica
this week with Norwegian Prime Minister Jens Stoltenberg to get a
firsthand view of the situation.
"You can read as much as you want on these subjects, but it doesn't
really enter your system. You don't really appreciate the enormity of
what you have," Pachauri said.
(c) 2008 The Washington Post Company
URL: http://www.msnbc.msn.com/id/22643132/
Sheets melting in an area once thought to be unaffected by global
warming
By Marc Kaufman
The Washington Post
updated 3:18 a.m. ET, Mon., Jan. 14, 2008
WASHINGTON - Climatic changes appear to be destabilizing vast ice
sheets of western Antarctica that had previously seemed relatively
protected from global warming, researchers reported yesterday, raising
the prospect of faster sea-level rise than current estimates.
While the overall loss is a tiny fraction of the miles-deep ice that
covers much of Antarctica, scientists said the new finding is
important because the continent holds about 90 percent of Earth's ice,
and until now, large-scale ice loss there had been limited to the
peninsula that juts out toward the tip of South America. In addition,
researchers found that the rate of ice loss in the affected areas has
accelerated over the past 10 years -- as it has on most glaciers and
ice sheets around the world.
"Without doubt, Antarctica as a whole is now losing ice yearly, and
each year it's losing more," said Eric Rignot, lead author of a paper
published online in the journal Nature Geoscience.
The Antarctic ice sheet is shrinking despite land temperatures for the
continent remaining essentially unchanged, except for the fast-warming
peninsula.
The cause, Rignot said, may be changes in the flow of the warmer water
of the Antarctic Circumpolar Current that circles much of the
continent. Because of changed wind patterns and less-well-understood
dynamics of the submerged current, its water is coming closer to land
in some sectors and melting the edges of glaciers deep underwater.
"Something must be changing the ocean to trigger such changes," said
Rignot, a senior scientist with NASA's Jet Propulsion Laboratory. "We
believe it is related to global climate forcing."
Rignot said the tonnage of yearly ice loss in Antarctica is
approaching that of Greenland, where ice sheets are known to be
melting rapidly in some parts and where ancient glaciers have been in
retreat. He said the change in Antarctica could become considerably
more dramatic because the continent's western shelf, an expanse of ice
and snow roughly the size of Texas, is largely below sea level and has
broad and flat expanses of ice that could move quickly. Much of
Greenland's ice flows through relatively narrow valleys in mountainous
terrain, which slows its motion.
'Frightening' possibility
The new finding comes days after the head of the Intergovernmental
Panel on Climate Change said the group's next report should look at
the "frightening" possibility that ice sheets in Greenland and
Antarctica could melt rapidly at the same time.
"Both Greenland and the West Antarctic ice sheet are huge bodies of
ice and snow, which are sitting on land," said Rajendra Pachauri,
chief of the IPCC, the United Nations' scientific advisory group. "If,
through a process of melting, they collapse and are submerged in the
sea, then we really are talking about sea-level rises of several
meters." (A meter is about a yard.) Last year, the IPCC tentatively
estimated that sea levels would rise by eight inches to two feet by
the end of the century, assuming no melting in West Antarctica.
The new Antarctic ice findings are based on mapping of 85 percent of
the continent over the past decade using radar data from European,
Japanese and Canadian weather satellites. Previous studies had
detected the beginning of ice loss in West Antarctica and substantial
loss along the peninsula, but the current research found significantly
greater changes.
Rignot and his team found that East Antarctica, which holds a majority
of the continent's ice, has not experienced the same kind of loss --
probably because most of the ice sits atop land rather than below sea
level, as in the west. In several coastal areas of East Antarctica,
however, small but similar losses have been detected, he said.
In all, snowfall and ice loss in East Antarctica have about equaled
out over the past 10 years, leaving that part of the continent
unchanged in terms of total ice. But in West Antarctica, the ice loss
has increased by 59 percent over the past decade to about 132 billion
metric tons a year, while the yearly loss along the peninsula has
increased by 140 percent to 60 billion metric tons. Because the ice
being lost is generally near the bottom of glaciers, the glacier moves
faster into the water and thins further, as a result. Rignot said
there has been evidence of ice loss going back as far as 40 years.
The new findings come as the Arctic is losing ice at a dramatic rate
and glaciers are in retreat across the planet. At a recent annual
meeting of the American Geophysical Union, Ohio State University
professor Lonnie Thompson delivered a keynote lecture that described a
significant speed-up in the melting of high-altitude glaciers in
tropical regions, including Peru, Tibet and Mount Kilimanjaro in
Kenya.
Thompson, who has studied the Quelccaya glacier in the Peruvian Andes
for 30 years, said that for the first half of that period, it
retreated on average 20 feet per year. For the past 15 years, he said,
it has retreated an average of nearly 200 feet per year.
"The information from Antarctica is consistent with what we are seeing
in all other areas with glaciers -- a melting or retreat that is
occurring faster than predicted," he said. "Glaciers, and especially
the high-elevation tropical glaciers, are a real canary in the coal
mine. They're telling us that major climatic changes are occurring."
While the phenomenon of ice loss worldwide is well documented, the
dynamics in the Antarctic are probably the least understood. Glaciers
and ice sheets are sometimes miles deep, and researchers do not know
what might be happening at the bottom of the ice -- but it clearly is
being lost along the peninsula and West Antarctic coast.
Rignot theorizes that the warmer water of the Antarctic Circumpolar
Current is the cause. Douglas Martinson, a senior research scientist
fellow at the Lamont-Doherty Earth Observatory of Columbia University,
has studied the issue and agrees.
Martinson said the current, which flows about 200 yards below the
frigid surface water, began to warm significantly in the 1980s, and
that warming in turn caused wind patterns to change in ways that
ultimately brought more warm water to shore. The result has been an
increased erosion of the glaciers and ice sheets.
Martinson said researchers do not have enough data to say for certain
that the process was set in motion by global warming, but "that is
clearly the most logical answer."
Pachauri, the IPCC's chief of climate science, will visit Antarctica
this week with Norwegian Prime Minister Jens Stoltenberg to get a
firsthand view of the situation.
"You can read as much as you want on these subjects, but it doesn't
really enter your system. You don't really appreciate the enormity of
what you have," Pachauri said.
(c) 2008 The Washington Post Company
URL: http://www.msnbc.msn.com/id/22643132/
