Gigantic cavity in Antarctic glacier signals rapid decay

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The massive cavity is about two-thirds of the area of Manhattan and is said to be nearly 1,000-feet tall and growing.

Thwaites Glacier is about the size of Florida and now responsible for roughly 4 percent of global sea rise.

Bute size and explosive growth rate of the newfound hole surprised them.

The largest part of the ice had melted within the last three years, and the resulting cavity is 350 meters high.

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"We have for years suspected that Thwaites is not firmly connected to the substrate", says Co-author Eric Rignot. He was ten kilometers long and four kilometers wide, and therefore as large as two-thirds of the area of Manhattan, write researchers at the Jet Propulsion Laboratory (JPL) of the United States space Agency Nasa in the journal "Science Advances".

Scientists spotted the concealed void thanks to a new generation of satellites, Rignot noted.

The data comes from NASA's Operation IceBridge, a program that flies radar-equipped planes over the poles to map out glaciers and ice sheets in three dimensions.

"[The size of] a cavity under a glacier plays an important role in melting", lead author Pietro Milillo, from NASA's Jet Propulsion Laboratory, said in a statement. The common thread among them is the infiltration of relatively warm ocean water below the ice, thinning it and causing the glaciers to flow out to sea faster. The mottled area (bottom left) shows extensive iceberg calving. A radar was used to peer through the ice to see to the bottom of the glacier. With climate change likely to continue accelerating this melt, the implications for global sea level rise are considerable. The International Thwaites Glacier Collaboration will begin its field experiments in the Southern Hemisphere summer of 2019-20.

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One recent study warned the "doomsday" Antarctic glacier that could collapse within decades. An advanced satellite that is able to use a radar array that can penetrate the thick layers of ice was the primary tool that led to the discovery.

Another changing feature is a glacier's grounding line - the place near the edge of the continent where it lifts off its bed and starts to float on seawater.

As the loss of these glaciers could result in the inundation of major cities, such as NY, new research teams are set to travel to this, one of the hardest to reach areas on Earth.

Periodically from the glacier break off huge icebergs, which are carried in the Amundsen sea and further North. Researchers believe that discovered the cavity is not the only one. In this region, as the tide rises and falls, the grounding line retreats and advances across a zone of about 2 to 3 miles (3 to 5 kilometers). The glacier has been coming unstuck from a ridge in the bedrock at a steady rate of about 0.6 km to 0.8 km a year since 1992. Nevertheless, the glacier melts more slowly here than on the West side. As they are melting and the formation of icebergs, the water will be even greater.

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Researchers hope the new findings will help others preparing for fieldwork in the area better understand the ice-ocean interactions. Additionally, there is another casualty besides the hidden cavity among the "complex pattern of retreat and ice melt". If those glaciers melted, too, sea levels could increase a whopping 8 feet (2.4 meters), the research team said.

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