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The
most precise record of Antarctic snowfall ever generated
shows there has been no real increase in precipitation
over the southernmost continent in the past half-century,
even though most computer models assessing global climate
change call for an increase in Antarctic precipitation
as atmospheric temperatures rise.
"The year-to-year and decadal variability of the
snowfall is so large that it makes it nearly impossible
to distinguish trends that might be related to climate
change from even a 50-year record," said Andrew Monaghan,
a research associate with Ohio State University's Byrd
Polar Research Center and lead author of an article on
the topic published in the Aug. 10 edition of Science
magazine.
"There were no statistically significant trends
in snowfall accumulation over the past five decades, including
recent years for which global mean temperatures have been
warmest," Monaghan said.
The findings also suggest thickening of Antarctica's
massive ice sheets haven't reduced the slow-but-steady
rise in global sea levels, as some climate-change critics
have argued.
The study looked at both the West Antarctic Ice Sheet
(WAIS), a marine ice sheet with a base below sea level,
and the much thicker East Antarctic Ice Sheet (EAIS) that
sits atop dry land. In recent years, large volumes of
ice along the WAIS coast have melted at a faster rate
than previously seen. Some observers have blamed global
warming for the melting and for the increased calving
of icebergs along the continent's margin.
The 16 researchers from nine institutions in seven countries
wanted to assemble a half-century-long record of snowfall
back to the International Geophysical Year, or IGY. Work
during the IGY began the first real modern study of the
Antarctic continent and substantive research has continued
there ever since. That work will continue in 2007-2008
during the upcoming International Polar Year (IPY), including
NSF-funded studies of ice-sheet dynamics.
The research team coupled data from existing ice cores
in the region, snow pits and networks of snow stakes,
and meteorological observations. To these they added numerous
new ice core records obtained by the International Transantarctic
Scientific Expedition (ITASE), a 12-nation research program
begun in 1990 and tasked with reconstructing the continent's
climate history. NSF funded the U.S. component of ITASE.
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National
Science Foundation -
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