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

The international Ocean Drilling Program, supported in largepart by the U.S. National Science Foundation (NSF), is conductinga two-month expedition near the edge of the Antarctic continent,the first of a series to probe the historical development of theAntarctic ice sheet and its consequences for earth's climate.

"Scientific drilling in the deep ocean is a window on thepast," explains Bruce Malfait, NSF ocean drilling programdirector. "Using composition, texture, fossil content and othersediment information, scientists can travel back in time." Insome places around Antarctica, for example, it may have taken1,000 years to deposit 10 centimeters of sediment. So drillingone kilometer of those sediment's then, would take researchersback 10 million years. A teaspoonful of mud one centimeter thickwould go back 100 years.

The Antarctic ice sheet is the world's largest, butscientists have many questions about how it grew, when, and why.Researchers aboard the JOIDES Resolution hope this expeditionwill help to answer those questions.

"We all know about the ice sheets of the northernhemisphere, including the very large masses of ice that coveredNorth America and northern Europe and Asia in recent times," saysPeter Barker of the British Antarctic Survey, co-chief scientistof the expedition. "But in geological terms, these ice sheetsare very young at only three million years old, as compared tothe ice surrounding Antarctica. Even the Greenland ice sheet isa comparative newcomer at seven million years old. Ice likelyexisted on Antarctica 35 million years ago."

Northern hemisphere ice sheets are very sensitive to climatechange. Scientists aboard the JOIDES Resolution will attempt todiscover whether that sensitivity holds true for Antarctic ice,and to what extent. Till deposits on the Antarctic margincontain a record of past behavior of the ice sheet. Sampling anddating the till should provide information on when and why theice sheet developed, and its effects on sea level and oceanchemistry through time.

"Mankind is on the edge of having the power to change globalclimate," says Barker. "If we are to make wise decisions onthis, we must understand how climate works -- what drives it, howquickly the various parts of the system respond, and what thefull effect would be of what we might do, or have done. Becauseof its pivotal importance to world climate, we must try tounderstand the history of the Antarctic ice sheet."

The expedition will conclude April 11 with a port call inCape Town, South Africa. The expedition targets the AntarcticPeninsula because its sediments are relatively well-mapped andeasy to interpret. Drilling in future seasons will examine othersectors of the Antarctic margin, if this expedition issuccessful.