Recently observed change in Arctic temperatures and sea
ice cover may be a harbinger of global climate changes to
come, according to a recent NASA study. Satellite data — the
unique view from space — are allowing researchers to more
clearly see Arctic changes and develop an improved
understanding of the possible effect on climate worldwide.

The Arctic warming study, appearing in the November 1 issue
of the American Meteorological Society’s Journal of Climate,
shows that compared to the 1980s, most of the Arctic warmed
significantly over the last decade, with the biggest
temperature increases occurring over North America.

“The new study is unique in that, previously, similar studies
made use of data from very few points scattered in various
parts of the Arctic region,” said the study’s author, Dr.
Josefino C. Comiso, senior research scientist at NASA’s
Goddard Space Flight Center, Greenbelt, Md. “These results
show the large spatial variability in the trends that only
satellite data can provide.” Comiso used surface temperatures
taken from satellites between 1981 and 2001 in his study.

The result has direct connections to NASA-funded studies
conducted last year that found perennial, or year-round, sea
ice in the Arctic is declining at a rate of nine percent per
decade and that in 2002 summer sea ice was at record low
levels. Early results indicate this persisted in 2003.

Researchers have suspected loss of Arctic sea ice may be
caused by changing atmospheric pressure patterns over the
Arctic that move sea ice around, and by warming Arctic
temperatures that result from greenhouse gas buildup in the
atmosphere.

Warming trends like those found in these studies could
greatly affect ocean processes, which, in turn, impact Arctic
and global climate, said Michael Steele, senior oceanographer
at the University of Washington, Seattle. Liquid water
absorbs the Sun’s energy rather than reflecting it into the
atmosphere the way ice does. As the oceans warm and ice
thins, more solar energy is absorbed by the water, creating
positive feedbacks that lead to further melting. Such
dynamics can change the temperature of ocean layers, impact
ocean circulation and salinity, change marine habitats, and
widen shipping lanes, Steele said.

In related NASA-funded research that observes perennial sea-
ice trends, Mark C. Serreze, a scientist at the University of
Colorado, Boulder, found that in 2002 the extent of Arctic
summer sea ice reached the lowest level in the satellite
record, suggesting this is part of a trend. “It appears that
the summer 2003 — if it does not set a new record — will be
very close to the levels of last year,” Serreze said. “In
other words, we have not seen a recovery; we really see we
are reinforcing that general downward trend.” A paper on this
topic is forthcoming.

According to Comiso’s study, when compared to longer term
ground-based surface temperature data, the rate of warming in
the Arctic over the last 20 years is eight times the rate of
warming over the last 100 years.

Comiso’s study also finds temperature trends vary by region
and season. While warming is prevalent over most of the
Arctic, some areas, such as Greenland, appear to be cooling.
Springtimes arrived earlier and were warmer, and warmer
autumns lasted longer, the study found. Most importantly,
temperatures increased on average by 1.22 degrees Celsius per
decade over sea ice during Arctic summer. The summer warming
and lengthened melt season appears to be affecting the volume
and extent of permanent sea ice. Annual trends, which were
not quite as strong, ranged from a warming of 1.06 degrees
Celsius over North America to a cooling of .09 degrees
Celsius in Greenland.

If the high latitudes warm, and sea ice extent declines,
thawing Arctic soils may release significant amounts of
carbon dioxide and methane now trapped in permafrost, and
slightly warmer ocean water could release frozen natural
gases in the sea floor, all of which act as greenhouse gases
in the atmosphere, said David Rind, a senior researcher at
NASA’s Goddard Institute of Space Studies, New York. “These
feedbacks are complex and we are working to understand them,”
he added.

The surface temperature records covering from 1981 to 2001
were obtained through thermal infrared data from National
Oceanic and Atmospheric Administration satellites. The
studies were funded by NASA’s Earth Science Enterprise, which
is dedicated to understanding the Earth as an integrated
system and applying Earth System Science to improve
prediction of climate, weather and natural hazards using the
unique vantage point of space.

For more information and images on the Internet, visit:
http://www.gsfc.nasa.gov/topstory/2003/1023esuice.html
and
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