Title : PR 93-57 World's Deepest Ice Core Yields Unique Climate Archive
Type : Press Release
NSF Org: OD / OPP
Date : July 15, 1993
File : pr9357
Lynn Simarski June 29, 1993
(202) 357-9498 NSF PR 93-57
WORLD'S DEEPEST ICE CORE THROUGH GREENLAND ICE SHEET
YIELDS UNIQUE CLIMATE ARCHIVE
After five years of drilling through the Greenland ice sheet, National Science
Foundation (NSF)-sponsored researchers have extracted the world's deepest ice
core reaching 3052 meters (10,013 feet) on June 29 and are about to hit rock
bottom. The 5.2" diameter core through the summit of the ice sheet, along
with a European core completed last year 30 kilometers (18.6 miles) away, is
furnishing the longest, most detailed record available of the Northern
Hemisphere's climate, reaching back about 250,000 years. Together, the cores
are altering ideas about the very nature of the earth's climate system. The
cores reveal a climate history whose dynamism has startled researchers. "The
biggest surprise so far is that climate changes much more rapidly and frequently
than we ever believed before," said Paul Mayewski, chief scientist for the
Greenland Ice Sheet Project (GISP 2), which includes scientists from more than
20 U.S. universities and laboratories, and is part of NSF's Arctic Systems
Science initiative. Patterns of past climate stored in the ice show that
climate changed substantially every few thousand years, until the end of the
last ice age.
One climatic interlude recorded in the ice, the so-called Younger Dryas, has
drawn great scientific attention because of its abrupt onset and conclusion,
as described by Richard B. Alley of Pennsylvania State University and coauthors
in the April 8, 1993, issue of the journal Nature. The last ice age ended
about 15,000 years ago and warmer temperatures reigned; about 2,000 years
later, climate chilled again dropping 7 degrees C in Greenland during the
Younger Dryas. Then, the earth switched very rapidly, in perhaps as little as
three years, to the relatively balmy conditions that have persisted until
What is more, climatic conditions over central Greenland also fluctuated back
and forth within just a few decades well within a human lifespan before
finally settling into a new state. These findings were described by Ken C.
Taylor of the Desert Research Institute and coauthors in the February 4, 1993,
issue of Nature. The swings in temperature and atmospheric chemistry recorded
inthe ice may reflect massive shifts in the circulation of the atmosphere and
oceans, researchers suggest.
The GISP core was drilled over five summers, during which about 50 scientists,
drillers, and camp staff have lived atop the flat, white expanse of the ice
meet, extracting and processing lengths of core. All staff and supplies are
flown in on ski-equipped LC-130 planes of the 109th Air National Guard of
Scotia, N.Y. The Polar Ice Coring Office of the University of Alaska-Fairbanks
developed the drill and outfitted the camp, while the GISP 2 Science Management
Office of the University of New Hampshire developed the core-processing
facility and coordinates the project.
The American and European ice cores harbor the best records of climate
obtainable--more continuous and with finer detail than the information stored
in tree rings, coral growth layers, or the annual sediments of lakes. The ice
archive was created as snow fell over Greenland year after year, trapping the
gases, chemicals, and dust of the atmosphere, which are valuable clues to
volcanic activity, biological productivity, desertification, and atmospheric
circulation at the time the snow fell. The layers of snow eventually
compressed together into the massive ice cap.
The Greenland cores comprise a unique record for the Northern Hemisphere,
particularly in light of evidence that the circulation of the north Atlantic
Ocean seems to play a key role in climate dynamics--possibly even triggering
the switch-overs between glacial and interglacial periods. The cores also
contain greater detail than the Antarctic cores currently available: the
annual ice layers in the cores from Antarctica, extracted at locations with
less snowfall than at the Greenland site, are thinner and harder to read.
The cores reveal that climate has been remarkably stable during the Holocene,
the period since the last ice age ended. "But the richly detailed record also
shows climate fluctuations during this time," Mayewski said. "These were
relatively minor compared to changes in glacial times, but had a significant
impact on human society." The Medieval Warm Period, for example, coincided
with Viking expansion into Iceland, Greenland, and Newfoundland, while the
Little Ice Age, from about 1400-1900 A.D., contributed to the abandonment of
colonies in the north Atlantic and northern Europe.
The cores may also shed light upon the consequences of the global warming
apparently being fostered by human activity. "It's clear that our climate
system has been capable of rapid change in the past," said Michael Morrison,
associate director of the GISP 2 Science Management Office, "while human
impact on the atmosphere is also obvious in the ice core.
"Industrial activity has actually changed the same constituents in the
atmosphere such as carbon dioxide, sulfate, nitrate, and methane that have
varied with natural climate changes in the past."
The climate history housed in such fine detail by the Greenland cores may
ultimately permit researchers to unravel the mechanisms of climate change and
help to assess whether human activity might once again set off such changes.
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