Photo/John McConnico) In this July 19, 2007 file photo, an iceberg melts
off Ammassalik Island in Eastern Greenland. More than 2 trillion tons of
land ice in Greenland, Antarctica and Alaska have melted since 2003,
according to new NASA satellite data that show the latest signs of what
scientists say is global warming
WASHINGTON (Map, News) - More than 2 trillion tons of land ice in
Greenland, Antarctica and Alaska have melted since 2003, according to
new NASA satellite data that show the latest signs of what scientists
say is global warming.
More than half of the loss of landlocked ice in the past five years
has occurred in Greenland, based on measurements of ice weight by NASA's
GRACE satellite, said NASA geophysicist Scott Luthcke. The water melting
from Greenland in the past five years would fill up about 11 Chesapeake
Bays, he said, and the Greenland melt seems to be accelerating.
NASA scientists planned to present their findings Thursday at the
American Geophysical Union conference in San Francisco. Luthcke said
Greenland figures for the summer of 2008 aren't complete yet, but this
year's ice loss, while still significant, won't be as severe as 2007.
The news was better for Alaska. After a precipitous drop in 2005,
land ice increased slightly in 2008 because of large winter snowfalls,
Luthcke said. Since 2003, when the NASA satellite started taking
measurements, Alaska has lost 400 billion tons of land ice.
In assessing climate change, scientists generally look at several
years to determine the overall trend.
Melting of land ice, unlike sea ice, increases sea levels very
slightly. In the 1990s, Greenland didn't add to world sea level rise;
now that island is adding about half a millimeter of sea level rise a
year, NASA ice scientist Jay Zwally said in a telephone interview from
Between Greenland, Antarctica and Alaska, melting land ice has raised
global sea levels about one-fifth of an inch in the past five years,
Luthcke said. Sea levels also rise from water expanding as it warms.
Other research, being presented this week at the geophysical meeting
point to more melting concerns from global warming, especially with sea
"It's not getting better; it's continuing to show strong signs of
warming and amplification," Zwally said. "There's no reversal taking
Scientists studying sea ice will announce that parts of the Arctic
north of Alaska were 9 to 10 degrees warmer this past fall, a strong
early indication of what researchers call the Arctic amplification
effect. That's when the Arctic warms faster than predicted, and warming
there is accelerating faster than elsewhere on the globe.
As sea ice melts, the Arctic waters absorb more heat in the summer,
having lost the reflective powers of vast packs of white ice. That
absorbed heat is released into the air in the fall. That has led to
autumn temperatures in the last several years that are six to 10 degrees
warmer than they were in the 1980s, said research scientist Julienne
Stroeve at the National Snow and Ice Data Center in Boulder, Colo.
That's a strong and early impact of global warming, she said.
"The pace of change is starting to outstrip our ability to keep up
with it, in terms of our understanding of it," said Mark Serreze, senior
scientist at the National Snow and Ice Data Center in Boulder, Colo., a
co-author of the Arctic amplification study.
Two other studies coming out at the conference assess how Arctic
thawing is releasing methane - the second most potent greenhouse gas.
One study shows that the loss of sea ice warms the water, which warms
the permafrost on nearby land in Alaska, thus producing methane, Stroeve
A second study suggests even larger amounts of frozen methane are
trapped in lakebeds and sea bottoms around Siberia and they are starting
to bubble to the surface in some spots in alarming amounts, said Igor
Semiletov, a professor at the University of Alaska in Fairbanks. In late
summer, Semiletov found methane bubbling up from parts of the East
Siberian Sea and Laptev Sea at levels that were 10 times higher than
they were in the mid-1990s, he said based on a study this summer.
The amounts of methane in the region could dramatically increase
global warming if they get released, he said.
That, Semiletov said, "should alarm people."
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