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Science

Turning Antarctic Ice-Making Upside Down

Antarctica has always been a focus for scientific understanding, given its comparative dissimilarities to the rest of our known world. But one thing was always pretty clear: the massive ice sheets that cover the southern continent form from the accumulation of snow falling on the top.

Right?

New evidence provided by researchers flying over East Antarctica’s Gamburtsev Mountain’s between November 2008 to January 2009 have had that particular idea turned on its head.

Literally.

The researchers found evidence of large scale ice making at the bottom of the continent’s ice sheet, as they went searching for mountains buried deep beneath the ice. As can be seen in the image, a radar profile of the ice as recorded on January 1, 2009, there is a massive block of frozen ice above the mountains.

“We usually think of ice sheets like cakes—one layer at a time, added from the top,” said Robin Bell, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory. “This is like someone injected a layer of frosting at the bottom—a really thick layer.”

According to the NASA Earth Observatory, the image shows the “rugged land beneath the ice, while the upper edge shows the flat, annual layering typical of ice formation from the top. In between, there is a jumbled mess unlike anything researchers had seen before.”

Their research shows that beneath Dome A, a plateau that forms the high point of the East Antarctic ice sheet, at least 24 percent of the ice formed from the bottom up: in other locations, as much as half of the ice sheet is formed from the bottom up.

Scientists believe that the water which melts at the lower levels of the ice sheet as a result of friction between the ice and the covered land surfaces or as a result of the natural heat radiating from the solid earth, especially when the ice is so well shielded from the freezing temperatures at the top of the ice sheet, can create large bodies of water just above the continental land mass.

With so much ice pressing down, and whatever heat there is below the sheet itself, scientists believed it would be very hard for freezing to take place.

But this new research suggests that the water is sometimes able to freeze if there is less pressure from above, or if it is able to squeeze up valley walls.

“Water has always been known to be important to ice sheet dynamics, but mostly as a lubricant,” Bell added. “As ice sheets change, we want to predict how they will change. Our results show that models must include water beneath.”

Source: NASA Earth Observatory




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