NSF PR 98-11 - February 17, 1998
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Why Is Antarctica So Cold?
Scientists Pursue History of Antarctic
Ice Sheet
Departing Punta Arenas, Chile, in mid-February, 26
scientists representing 10 countries will sail aboard
the ocean drilling ship JOIDES Resolution to collect
core samples from the continental rise and shelf of
the Antarctic Peninsula.
The international Ocean Drilling Program, supported
in large part by the U.S. National Science Foundation
(NSF), is conducting a two-month expedition near the
edge of the Antarctic continent, the first of a series
to probe the historical development of the Antarctic
ice sheet and its consequences for earth's climate.
"Scientific drilling in the deep ocean is a window
on the past," explains Bruce Malfait, NSF ocean drilling
program director. "Using composition, texture, fossil
content and other sediment information, scientists
can travel back in time." In some places around Antarctica,
for example, it may have taken 1,000 years to deposit
10 centimeters of sediment. So drilling one kilometer
of those sediment's then, would take researchers back
10 million years. A teaspoonful of mud one centimeter
thick would go back 100 years.
The Antarctic ice sheet is the world's largest, but
scientists have many questions about how it grew,
when, and why. Researchers aboard the JOIDES Resolution
hope this expedition will help to answer those questions.
"We all know about the ice sheets of the northern
hemisphere, including the very large masses of ice
that covered North America and northern Europe and
Asia in recent times," says Peter Barker of the British
Antarctic Survey, co-chief scientist of the expedition.
"But in geological terms, these ice sheets are very
young at only three million years old, as compared
to the ice surrounding Antarctica. Even the Greenland
ice sheet is a comparative newcomer at seven million
years old. Ice likely existed on Antarctica 35 million
years ago."
Northern hemisphere ice sheets are very sensitive
to climate change. Scientists aboard the JOIDES Resolution
will attempt to discover whether that sensitivity
holds true for Antarctic ice, and to what extent.
Till deposits on the Antarctic margin contain a record
of past behavior of the ice sheet. Sampling and dating
the till should provide information on when and why
the ice sheet developed, and its effects on sea level
and ocean chemistry through time.
"Mankind is on the edge of having the power to change
global climate," says Barker. "If we are to make wise
decisions on this, we must understand how climate
works -- what drives it, how quickly the various parts
of the system respond, and what the full effect would
be of what we might do, or have done. Because of its
pivotal importance to world climate, we must try to
understand the history of the Antarctic ice sheet."
The expedition will conclude April 11 with a port
call in Cape Town, South Africa. The expedition targets
the Antarctic Peninsula because its sediments are
relatively well-mapped and easy to interpret. Drilling
in future seasons will examine other sectors of the
Antarctic margin, if this expedition is successful.
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