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Scientists Pinpoint Polar Cataclysm Date

(AP) -- A 30-mile maze canyons in Antarctica was carved out of bedrock by the catastrophic draining of subglacial lakes during global warming between 12 million and 14 million years ago, according to university researchers who warn a similar event today could have serious environmental consequences.

Although scientists have previously theorized that the Labyrinth region in southern Victoria Land was created by water released from lakes that had formed under glaciers, researchers at Syracuse University and Boston University say they found geological evidence to bracket the timing of the last major flooding and link it to a global warming trend at the time.

The scientists pinpointed the timing of the last subglacial flood by dating volcanic ash preserved on bedrock surfaces, said Laura Webb, a professor of earth sciences at Syracuse who took part in the study.

The Labyrinth is a network of ice-free bedrock channels and scoured terrain emerging from beneath the East Antarctic Ice Sheet. It is one of a series of large channel networks that cross the Transantarctic Mountains. Some of the chasms are up to 800 feet deep and thousands of feet wide. Scientists have long speculated that the volume of water required to create the channels was far more than that produced by melting glaciers.

Webb said it appeared the subglacial flooding was not continuous but episodic, and likely lasted days or months at a time.

In an article on the study that appeared last month in the journal "Geology," Webb and her colleagues estimated the flood raged with approximately 1,000 times the volume of water flowing over Niagara Falls. At that rate, it would take Lake Ontario, for instance, about a month to drain, she said.

Suzanne Baldwin, another Syracuse professor who was one of the study's principal researchers, warned that the ancient episode has implications for global climate change today.

Subglacial lakes in Antarctica were first identified in the 1960s, some sealed beneath up to 2 1/2 miles of ice. Since then, more than 150 have been discovered. But it is thought thousands may exist. The largest is Lake Vostok, similar in size to Lake Ontario. Another is the size of Rhode Island.

Baldwin and her colleagues believe there must be a more complete investigation of how a similar catastrophic release might alter the present-day environment.

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Such a massive release of fresh water from the subglacial lakes would affect the stability of the East Antarctic ice sheet, the circulation of water in the Southern Ocean, and global weather patterns, all of which could change the balance of the Earth's ecosystems, she said.

Dominic Hodgson, a geologist at the British Antarctic Survey, said formation of the Labyrinth has been attributed to subglacial meltwater since at least 1993, but the Syracuse study provided a "better estimate" of the timing of its creation.

Hodgson, who has written extensively about global warming and its impact on Antarctica, said some lake water discharges are contemporary. One such rapid discharge occurred in 1997-1998 when a one-mile-square lake emptied into two other downstream lakes under the ice sheet over a period of 16 months.

"It is very unlikely that the volume of these discharges would equal those of the Miocene (epoch), when the Labyrinth formed, because the ice sheet then was much more dynamic and temperate and therefore likely contained - and discharged - substantially greater volumes of subglacial meltwater," Hodgson said.

The British scientist said that present day global warming has not had any measured effects on the volume or movement of subglacial meltwater beneath the Antarctic ice sheet "so it is premature to predict a new era of flooding as a result of global warming."

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