M
mary collins
Guest
September 25, 2007 http://earthobservatory.nasa.gov/Newsroom/NasaNews/2007/2007092525665.html
'REMARKABLE' DROP IN ARCTIC SEA ICE RAISES QUESTIONS
Melting Arctic sea ice has shrunk to a 29-year low, significantly
below the minimum set in 2005, according to preliminary figures from
the National Snow and Ice Data Center, part of the University of
Colorado at Boulder. NASA scientists, who have been observing the
declining Arctic sea ice cover since the earliest measurements in
1979, are working to understand this sudden speed-up of sea ice
decline and what it means for the future of Earth's northern polar
region.
"The decline in the amount of thick ice that survives the summer melt
season this year is quite remarkable," said Josefino C. Comiso, senior
scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "The
extent of this 'perennial' sea ice and the area it covers are both
nearly 38 percent lower than average. Compared to the record low in
2005, the extent and area are 24 percent and nearly 26 percent lower
this year, respectively."
"From what we know of how Arctic sea ice behaves after nearly 30 years
of continuous satellite observations, this kind of drop in sea ice
usually takes more than three years to happen. The rapid trend of the
perennial ice previously reported in 2002 appears now to be in an
accelerated mode," Comiso observed.
Because Arctic ice cover varies so much year to year, it can be
dangerous to look at any one year and draw too much of a conclusion
from it," said Waleed Abdalati, head of Goddard's Cryospheric Sciences
Branch. "But this year, the amount of ice is so far below that of
previous years that it really is cause for concern. The trend in
decreasing ice cover seems to be getting stronger and stronger as time
goes on."
NASA developed the original capability to observe the extent and
concentration of sea ice from space using passive microwave sensors.
More recently, NASA launched an advanced microwave instrument in 2002
-- the Advanced Microwave Scanning Radiometer (AMSR-E) on the Aqua
satellite -- that provides a view of sea ice dynamics in greater
detail than has ever been seen before. Researchers use this
information to study polar bear habitats and the unique movements of
sea ice from season to season. AMSR-E is a joint project of NASA and
the National Space Development Agency of Japan.
The accelerating decline in sea ice may be due to changes in climate
brought on by the lack of sea ice itself, Comiso believes. "When there
is less sea ice in the summer, the Arctic Ocean receives more heat.
The warmer water makes it harder for the ice to recover in the winter,
and, therefore, there is a higher likelihood that sea ice will retreat
farther during the summer. This process repeats itself year after
year," Comiso said.
"The longer this process continues, the less likely recovery becomes,"
Abdalati believes. "The implications on global climate are not well
known, but they have the potential to be quite large, since the Arctic
ice cover exhibits a tremendous influence on our climate. It really is
imperative that we try to understand the interactions between the ice,
ocean and atmosphere. And satellites hold the key to developing this
understanding."
Current satellites, however, can map sea ice in two dimensions, but it
is much more difficult to find out how the thickness of the ice
contributes to the change in the total volume of the ice. NASA's
ICESat spacecraft (Ice, Cloud, and land Elevation Satellite), launched
in 2003, with the primary goal of determining how much ice sheets are
contributing to sea-level rise. ICESat is also collecting data that
enables scientists to make estimates of sea ice thickness with
unprecedented detail.
"What we need to truly understand the interaction of the ice, ocean
and atmosphere in the Arctic is sea ice thickness information," said
Abdalati. "The new capability we have with ICESat is expected to be
extended into the next decade based on recent recommendations by the
National Research Council for a follow-on mission. Ultimately, like
the 29-year record we have now of sea ice cover, a long-term ice
thickness record will help scientists understand these complex
interactions and what the changes in the ice cover will mean to the
ecology of the Arctic and to life on Earth."
For more information, visit:
http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html
http://www.nasa.gov/vision/earth/environment/seaice_meltdown.html
http://www.jpl.nasa.gov/news/news.cfm?release=2006-107
http://icesat.gsfc.nasa.gov/
'REMARKABLE' DROP IN ARCTIC SEA ICE RAISES QUESTIONS
Melting Arctic sea ice has shrunk to a 29-year low, significantly
below the minimum set in 2005, according to preliminary figures from
the National Snow and Ice Data Center, part of the University of
Colorado at Boulder. NASA scientists, who have been observing the
declining Arctic sea ice cover since the earliest measurements in
1979, are working to understand this sudden speed-up of sea ice
decline and what it means for the future of Earth's northern polar
region.
"The decline in the amount of thick ice that survives the summer melt
season this year is quite remarkable," said Josefino C. Comiso, senior
scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "The
extent of this 'perennial' sea ice and the area it covers are both
nearly 38 percent lower than average. Compared to the record low in
2005, the extent and area are 24 percent and nearly 26 percent lower
this year, respectively."
"From what we know of how Arctic sea ice behaves after nearly 30 years
of continuous satellite observations, this kind of drop in sea ice
usually takes more than three years to happen. The rapid trend of the
perennial ice previously reported in 2002 appears now to be in an
accelerated mode," Comiso observed.
Because Arctic ice cover varies so much year to year, it can be
dangerous to look at any one year and draw too much of a conclusion
from it," said Waleed Abdalati, head of Goddard's Cryospheric Sciences
Branch. "But this year, the amount of ice is so far below that of
previous years that it really is cause for concern. The trend in
decreasing ice cover seems to be getting stronger and stronger as time
goes on."
NASA developed the original capability to observe the extent and
concentration of sea ice from space using passive microwave sensors.
More recently, NASA launched an advanced microwave instrument in 2002
-- the Advanced Microwave Scanning Radiometer (AMSR-E) on the Aqua
satellite -- that provides a view of sea ice dynamics in greater
detail than has ever been seen before. Researchers use this
information to study polar bear habitats and the unique movements of
sea ice from season to season. AMSR-E is a joint project of NASA and
the National Space Development Agency of Japan.
The accelerating decline in sea ice may be due to changes in climate
brought on by the lack of sea ice itself, Comiso believes. "When there
is less sea ice in the summer, the Arctic Ocean receives more heat.
The warmer water makes it harder for the ice to recover in the winter,
and, therefore, there is a higher likelihood that sea ice will retreat
farther during the summer. This process repeats itself year after
year," Comiso said.
"The longer this process continues, the less likely recovery becomes,"
Abdalati believes. "The implications on global climate are not well
known, but they have the potential to be quite large, since the Arctic
ice cover exhibits a tremendous influence on our climate. It really is
imperative that we try to understand the interactions between the ice,
ocean and atmosphere. And satellites hold the key to developing this
understanding."
Current satellites, however, can map sea ice in two dimensions, but it
is much more difficult to find out how the thickness of the ice
contributes to the change in the total volume of the ice. NASA's
ICESat spacecraft (Ice, Cloud, and land Elevation Satellite), launched
in 2003, with the primary goal of determining how much ice sheets are
contributing to sea-level rise. ICESat is also collecting data that
enables scientists to make estimates of sea ice thickness with
unprecedented detail.
"What we need to truly understand the interaction of the ice, ocean
and atmosphere in the Arctic is sea ice thickness information," said
Abdalati. "The new capability we have with ICESat is expected to be
extended into the next decade based on recent recommendations by the
National Research Council for a follow-on mission. Ultimately, like
the 29-year record we have now of sea ice cover, a long-term ice
thickness record will help scientists understand these complex
interactions and what the changes in the ice cover will mean to the
ecology of the Arctic and to life on Earth."
For more information, visit:
http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html
http://www.nasa.gov/vision/earth/environment/seaice_meltdown.html
http://www.jpl.nasa.gov/news/news.cfm?release=2006-107
http://icesat.gsfc.nasa.gov/
