NASA satellite shows 'dramatically thinned' Arctic ice
Arctic sea ice thinned dramatically between the winters of 2004 and
2008, with thick older ice shrinking by the equivalent of Alaska's land
area, a study using data from a NASA satellite showed Tuesday.
Using information from NASA's Ice, Cloud and Land Satellite (ICESat),
scientists from the US space agency and the University of Washington in
Seattle estimated both the thickness and volume of the Arctic Ocean's
ice cover.
ICESat allows scientists to measure changes in the thickness and
volume of Arctic ice, whereas previously scientists relied only on
measurements of area to determine how much of the Arctic Ocean is
covered in ice.
Scientists found that Arctic sea ice thinned some seven inches (17.8
centimeters) a year, or 2.2 feet (67 centimeters) over four winters,
according to the study by NASA and the University of Washington,
published in the Journal of Geophysical Research-Oceans.
They also found that thicker, older ice, which has survived one or
more summers, shrank by 42 percent.
"Between 2004 and 2008, multi-year ice cover shrank 595,000 square
miles (1.5 million square kilometers) - nearly the size of Alaska's land
area," a report of the study's findings said.
The Arctic ice cap grows each winter, when the northerly region grows
intensely cold as the sun sets for several months.
Then, in the summer, wind and ocean currents cause some of the ice to
flow out of the Arctic, while warmer temperatures make much of it melt
in place.
Thicker, older ice is less vulnerable than thinner ice to melting in
the summer months. But in recent years, the amount of ice replaced in
the winter has not been sufficient to offset summer ice losses, the
ICESat study showed.
That makes for more open water in summer, which absorbs more heat,
warming the ocean and further melting the ice, the report of the
scientists' findings said.
The research team attributed the changes in the overall thickness and
volume of Arctic Ocean sea ice to recent warming and anomalies in
patterns of sea ice circulation.
"The near-zero replenishment of the multi-year ice cover, combined
with unusual exports of ice out of the Arctic after the summers of 2005
and 2007, have both played significant roles in the loss of Arctic sea
ice volume," said Ron Kwok of NASA's Jet Propulsion Laboratory in
California who led the study.
Data from the study will help scientists to better understand how
fast the volume of Arctic ice is decreasing and how soon the region
might be "nearly ice-free in the summer," said Kwok.
A study published in April by the Colorado-based National Snow and
Ice Data Center (NSIDC) also showed that the Arctic ice cap is thinner
than ever and the maximum extent of Arctic ice was at an all-time low.
The same month, US researchers warned that the Arctic could be almost
ice-free within 30 years, not 90 as scientists had previously estimated.
WASHINGTON, AFP |