• Eli is a contributing correspondent for Science magazine.

Gigantic Remelted Ice Mass Discovered Below Antarctic Ice Sheet

3 March 2011 5:41 pm

Unless the South Pole melts, no one is ever going to see the Gamburtsev Mountain Range. The "Antarctic Alps" has been encased beneath the East Antarctic Ice Sheet for millions of years. Yet thanks to radar and other technologies, scientists have begun to peer through the ice. And in a new study, they've uncovered startling insights into how it formed.

Until now, researchers have assumed the vast majority of the ice that makes up ice sheets forms as snowflakes compact over millions of years. But that may not be the whole story, according to the first major finding from data gathered as part of a seven-nation project known as the Antarctica's Gamburtsev Province (AGAP).

AGAP's focus in the new study was on the so-called "Dome A" region of the Gamburtsev range, the high point of the East Antarctic sheet. To image the ice below the frigid surface, scientists used two Twin Otter aircraft equipped with ice-penetrating radars, laser ranging systems, gravity meters, and sensors that measure magnetic fields. The planes scanned the surface in north-south flights spaced 5 kilometers apart, crossing in east-west lines every 33 kilometers.

Previous studies have found temperatures below the ice sheet, caused by the warmth of the planet below, that could melt water. But scientists thought there was much less meltwater, playing a far less important role in ice sheet structure, than the new work suggests. According to the observations, massive ice blocks seem to form when liquid water—propelled by the pressure of the ice—moves up the steep walls of the Gamburtsev mountains, says lead author and glaciologist Robin Bell of Lamont-Doherty Earth Observatory of Columbia University in Palisades, New York. As the water rises, it encounters lower temperatures and less pressure from overlying ice, so it refreezes.

In all, refrozen meltwater may be responsible for as much as half the thickness of the ice sheet over large areas, the team reports online today in Science. (Bell says clues suggest the same process occurs in Greenland and on the west side of the Antarctic ice sheet.)

It's too early to know whether this new finding means that global warming will melt ice sheets slower or faster than scientists have predicted. But the work does suggest that current models of ice sheet dynamics are missing a huge factor, said glaciologist Donald Blankenship of the University of Texas, Austin. "The take-home message of this work is that [the bottom of ice sheets] can no longer be ignored" in the models, he says.

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