-
- An analysis of sediments from the subtropical Atlantic
Ocean deposited during Earth's last glacial period indicate sudden
temperature
fluctuations were as large as those seen in the warming at
the end of the
last ice age, raising concerns about future climate
change.
-
- Scott Lehman, a research associate at CU-Boulder's Institute
of
Arctic and Alpine Research, said the study indicated the temperature
of
the Sargasso Sea between the West Indies and the Azores fluctuated
repeatedly
by up to 9 degrees Fahrenheit from 60,000 to 30,000 years
ago.
-
- "What is new here is clear evidence that the warm
Atlantic, like the polar Atlantic, was undergoing very large and very
rapid
temperature changes during the last glacial period."
-
- Instrumental climate
records and models indicate changes
in warm ocean temperatures are
likely to produce widespread, global climate
impacts, he said. The
impacts are due in part to the vast surface area
of Earth's warm oceans
and the fact that warm oceans create much more water
vapor, increasing
atmospheric heat trapping.
-
- "The temperature of the warm ocean realm regulates
the water vapor content of the atmosphere and its greenhouse
capacity,"
he said. Past temperature records and climate models
suggest ocean circulation
changes, like those in the last glacial
period, can be triggered by human
activity, showing that "the
impact of possible future circulation
changes may be more dramatic and
widespread than suspected."
-
- A paper on the subject by
Lehman and Julian Sachs, a
former CU-Boulder researcher at INSTAAR now
at Columbia University's Barnard
College, will appear in the Oct. 22
issue of Science, the nation's premier
weekly science magazine.
-
- Lehman and Sachs
reached their conclusions after studying
50 meters of sediment cores
hauled up from several miles deep in the Sargasso
Sea near Bermuda by
French scientists as part of an international project.
The CU
researchers analyzed the saturation state of organic molecules from
planktonic algae over the past 100,000 years, providing sea-surface
temperatures
during that period.
-
- "The warming at the end of
the last ice age about
10,000 years ago was supported by the
disappearance of enormous ice sheets,
a one-third increase in
atmospheric carbon dioxide levels and changes in
the seasonal
distribution of the sun's energy," Lehman said. "But
the
abrupt changes we documented during the last ice age seem to be almost
entirely ocean driven."
-
- Freshening of Earth's oceans is believed to have the
ability to trigger abrupt and long-lasting cooling events, including ice
ages, by interfering with the conveyor belt of water carrying heat from
the tropics to temperate regions. "Numerical modeling studies show
that similar changes can be triggered by warming associated with human
emissions as well," said Lehman.
-
- "Trapping more heat in the
atmosphere has the potential
to kill major parts of ocean circulation,
with the effects reverberating
throughout the world," he
said.
-
- A
1999 study by INSTAAR's Don Barber and colleagues showed
the collapse
of two gigantic glacial lakes near Hudson Bay about 8,000
years ago
poured enough fresh water into the Northern Atlantic to shut
down the
ocean circulation for several centuries, cooling Europe and Greenland
by some 6 degrees F.
-
- The last 8,000 years have been remarkably stable in
terms
of climate, considering the large temperature fluctuations, said
Lehman.
"By altering the environment through greenhouse gas
emissions, we
will likely find out how fragile the stability of Earth's
climate really
is. We may well find out we are dealing with a hair
trigger."
-
- The next step is to determine if similar changes occurred
in
the much larger Pacific Ocean, said Lehman. "If so, any human-induced
changes to the ocean's plumbing are likely to affect everyone on Earth,
not just Greenlanders and Northern Europeans."
-
-
- Editor's Note: The original news release can be found
at http:/
/www.colorado.edu/PublicRelations/NewsReleases/1999/334.html
-
- Note: This story has
been adapted from a news release
issued by University Of Colorado At
Boulder for journalists and other
members of the public. If you wish
to quote from any part of this story,
please credit University Of
Colorado At Boulder as the original source.
You may also wish to
include the following link in any citation: http://www.scien
cedaily.com/releases/1999/10/991025080116.htm
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