Millions Of Years Of Climate Clues

Scientists believe a 50-million-year record of the Earth's climate lies in an underwater mountain chain in the ice-clogged waters near the North Pole.

Beginning this month, an international team is drilling deep into the Arctic Ocean ridge for the first time, in a technically complex effort to extract sediment that will provide a climatic history, and may help explain how humans are changing the planet.

"Think of it as a book," said Kate Moran, an associate professor in the ocean engineering department at the University of Rhode Island and a co-chair of the Arctic Coring Expedition. "We're turning back the pages of time."

Scientists have wanted to make this trip for decades, but have never had the combination of icebreaking ships and advanced drilling equipment used by the oil industry to pull it off.

For much of the expedition, which is expected to end in mid-September, researchers will be perched above the Lomonosov Ridge, about 155 miles from the North Pole. They'll drill three 1,640-foot holes beneath the sea floor to extract the sediments needed to get a complete historical record. The cores will be taken to the University of Bremen, in Germany, for further analysis.

The team hopes the sediment samples will help them better understand two major components housed in the Arctic that are widely believed to determine the Earth's climate. The first is freshwater runoff and its effect on deep water currents that regulate ocean temperatures, and the second is sea ice that reflects the sun and acts as the Earth's thermostat.

Glaciers, the sun and the Earth's rotation and orbit are considered the other main factors affecting climate.

Theories as to how the Arctic affects climate have been mostly "educated guesswork," say the expedition's leaders on the trip's Web site. Moran calls the Arctic a "big black box" because of the region's importance to climate and scholars' lack of knowledge about it.

Scientists believe the oceans were about 10 degrees Fahrenheit warmer 50 million years ago, and then began to freeze, resulting in a mini Ice Age that began about 3 million years ago and lasts until today. The questions they want to answer are why the freezing began and how rapidly it occurred.

Today, scientists say, the Arctic ice packs are diminishing. The expedition says the packs have receded in the last three decades by 5 percent, roughly the size of France and Germany combined. Without these masses, many say, the Earth will continue to warm as it absorbs more heat, because there's less surface ice to reflect the sun's rays.

Moran said the sediment extracts will show how much sea ice has vanished, and when.

"We probably will see a continued decrease in sea ice, but we don't know how rapidly those changes will affect climate," Moran said in a telephone interview with The Associated Press from the Swedish icebreaker Oden. "So, we'll use the sediment record to see how quickly or slowly sea ice formed in the Arctic."

The extracts also could show how ocean currents that originate in the North Atlantic and flow worldwide affect climate. The current, much like a conveyor belt, carries cold water southward to Antarctica and onward to the Pacific and Indian oceans, where the water is warmed and returned to the Arctic.

With continued global warming and melting of Arctic ice, the current may weaken, ultimately decreasing the flow of warm water to Europe and causing a cooling of its climate. Still, no one is sure exactly what the effect on global climate would be.

"That's still up for grabs," said Amos Winter, a paleo-oceanography professor from the University of Puerto Rico who is in residence at the National Science Foundation.

Meanwhile, other scientists, including expedition co-chair Jan Backman of Stockholm University, will examine organisms — those fossilized in the sediment and living ones believed to be dwelling within the Earth's belly.

David Smith, a biological oceanographer at the University of Rhode Island, speculates as much as 10 percent of the Earth's biomass lives below ground. It includes single-celled bacteria called archaea that feed on decaying matter as it continues to fall to the sea floor, forming layers upon layers of sediment. He and others will use the Arctic findings to determine whether life is as abundant below ground as some think.

"There's no reason to believe there is no life," said Smith, who has been at the university since 1997. "The real question is how much life is there."

By Richard C. Lewis