[Homestead] Dynamics of global climate system
tvoivozd at infionline.net
Tue Sep 21 11:59:00 EDT 2004
University Of California - Santa Barbara <http://www.ucsb.edu/>
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Past Antarctic Ice Sheet Development Linked To Ocean Temperatures
And Carbon Dioxide
Santa Barbara, Calif.) –– New research published in the September 17
issue of the journal Science sheds light on the evolution of Earth's
climate system by identifying changes in temperature, ocean circulation,
and global carbon cycling associated with the rapid growth of Antarctic
ice sheets approximately 14 million years ago.
/View of East Antarctic Ice Sheet from Australia's Mawson Station.
(Photo Credit: Katharine Burgdorff)/
*Why Is Antarctica So Cold? Scientists Pursue History Of Antarctic Ice
*Global Warming Could Trigger Cascade Of Climatic Changes
*Antarctica Key To Sudden Sea Level Rise In The Past
/> more *related stories
*Earth & Climate <http://www.sciencedaily.com/news/earth_climate.htm>*
By studying chemical changes in deep sea sediments, scientists at the
University of California, Santa Barbara discovered that high-latitude
Southern Ocean cooling helped to trigger this major expansion of
Antarctic ice sheets, which have since become a permanent feature of the
global climate system. These results document ice sheet history and
supply crucial insight into the dynamics of the global climate system.
Scientists have long recognized that the Southern Ocean and the
development of Antarctic ice sheets play a major role in the evolution
of Earth's present climate system. Only now have researchers been able
to obtain a clearer picture of the relationship between high-latitude
temperatures, global carbon cycling and the size of Antarctic ice sheets.
Southern Ocean temperature data exhibits a rapid 7 degree cooling of
surface waters around 14 million years ago and suggests a strengthening
of the Antarctic Circumpolar Current in response to changes in the
geometry of Earth's orbits. As a result, Antarctica became increasingly
isolated from tropical heat and moisture sources. Records of Antarctic
ice volume indicate that following this cooling ice sheets expanded
rapidly to near present-day size, which suggests that changes in the
Southern Ocean directly influence the size of the Antarctic ice sheet.
UCSB researchers speculate that the climate system responded quickly to
orbital variations because of generally low atmospheric carbon dioxide
levels and plate tectonic changes north and south of Australia.
"Our study indicates that the sensitivity of Earth's climate system can
shift rapidly when climate boundary conditions, such as atmospheric
greenhouse gas levels or the configuration of the continents, change,"
said Amelia Shevenell, the lead author of the Science study and a Ph.D.
candidate at UCSB.
"Our results suggest that scientifically it is somewhat incidental
whether these boundary conditions are altered via natural or
human-induced processes," she said. "If the boundary conditions change,
we should expect Earth's climate system to respond."
Shevenell and co-authors Jim Kennett and David Lea, both professors of
Geological Sciences at UCSB, developed the records of Southern Ocean sea
surface temperature change, Antarctic ice volume, and global carbon
cycling by measuring chemical changes in the fossilized skeletal remains
of marine plankton contained in deep-sea sediments. Shevenell and
Kennett collected these sediments south of Tasmania when they sailed as
scientists on the Ocean Drilling Program's drill ship, the JOIDES
This research was supported by the National Science Foundation and Joint
*Editor's Note:* The original news release can be found here
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