Why Is Antarctica So Cold? Scientists Pursue History Of Antarctic Ice Sheet

February 17, 1998

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.

National Science Foundation

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