Mysterious South American glaciers grow as others shrink

June 23rd, 2009 - 1:39 pm ICT by ANI  

National Geographic Washington, June 23 (ANI): In times when most glaciers in the world are shrinking due to global warming, two mysterious South American glaciers are displaying strange behavior in the sense that they are growing.

“Most of the 50 massive glaciers draped over the spine of the Patagonian Andes are shrinking in response to a global warming,” said Andres Rivera, a glaciologist at the Center for Scientific Studies in Valdivia, Chile.

But, according to a report in National Geographic News, the Perito Moreno glacier in Argentina and Pio XI glacier in Chile are taking on ice, instead of shedding it.

“What is happening is not well understood,” Rivera said.

Theories center on the geography and topography of the glaciers; the depth and temperature of the waters where the glaciers end; and how quickly, or slowly, they react to changes in the climate.

Yet overall, “if you account for the gains and losses of all of Patagonia’s glaciers, they are (still) losing huge amounts of ice,” Rivera pointed out.

“One hypothesis for the 3-mile-wide (5 kilometer-wide) Perito Moreno’s advance is the glacier’s apparent insensitivity to changes in what glaciologists call the equilibrium line on glaciers,” Rivera said.

As a result, the amount of ice lost or gained is minimal.

It could also be that Perito Moreno simply hasn’t got all that much to lose.

Lago Argentino, the lake where Perito Moreno ends, is shallower than the bodies of water at the ends of most glaciers.

Most glaciers calve, or release ice, in deep water, but not Perito Moreno, where the calving rates are higher than on other Patagonian glaciers.

That means less of the glacier is in the melting zone below the equilibrium line.

As heavy snowfall above the equilibrium line pushes the glacier downhill, the glacier breaks up when it hits the lake, Rivera explained.

“Such impacts kept the glacier from growing longer when the climate was cooler, and thus more likely to expand,” he said.

As for the Pio XI glacier in Chile, some scientists have attempted to explain its advance as a glacial surge, a periodic and sudden expansion of a glacier that is little understood but is thought to be unrelated to external forces. (ANI)

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