By Karina Grazina

MARAMBIO BASE, Antarctica, March 14 (Reuters) - A glacier used as a benchmark to measure global warming's impact on the Antarctic Peninsula melted more than usual in the past year, according to an Argentine glacier researcher.

For more than 20 years, Pedro Skvarca has studied the Devil's Bay glacier on Vega Island off the Antarctic Peninsula, a part of Antarctica that is warming five times faster than the average in the rest of the world.

The whole of Antarctica holds enough ice and snow to raise world sea levels by 187 feet (57 meters) if it all melted over thousands of years, according to U.N. data.

Skvarca said the Devil's Bay glacier has thinned by 3.3 feet (1 meter) per year on average since his research began. But its deterioration has been unusually marked in the past year.

"We've observed a tremendous ablation (during the past year), which is really unusual," Skvarca, head of the Argentine Antarctic Institute's Glaciology Division, told Reuters in an interview at Argentina's main center for studying Antarctica, the Marambio base.

Ablation is the melting and falling away of ice in the zone at the foot of a glacier.

"(Last year) I put a box with a thermometer in it next to a marker that was level with the top of the ice. I found it half a meter in the air hanging from a wire," he said last week.

ICE MASSES

Skvarca said the glacier at Devil's Bay was the only Antarctic glacier to have its mass balance tracked consistently in recent years.

Mass balance is the difference between what is added to a glacier from snow or ice accumulation in the winter and what is melted or falls away in the summer.

"This is important because if you add up the mass balance of all the world's glaciers, we have very clear indications that we're in a period of atmospheric warming and receding glaciers," he said as he prepared to take a military flight home at the end of his annual studies during the Southern Hemisphere's summer.

The Antarctic Peninsula, which stretches from Antarctica toward South America, is considered an important area for studying climate change because of the effect it has had on the continent's ice masses.

Some of the huge ice shelves that line the peninsula's coasts have disintegrated, floating in chunks in the ocean.

A large part of the Larsen ice shelf broke off in 1995. In 2002, another section floated away, creating a 500 billion tonne iceberg as big as Luxembourg.

Ice shelves, which lie on top of the sea and are attached to land, are present along more than 40 percent of the Antarctic coastline. They are key to the stability of glaciers since they stop them from falling into the sea.

Skvarca is now closely watching the evolution of glaciers that once fed into the Larsen ice shelves.

"We're seeing the first signs of how the break-up of the shelves affects the glaciers that feed them," he said. (Reporting by Karina Grazina; Translated by Fiona Ortiz)

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