Saturday, 23 February, 2019

NASA Study Of Antarctic Glacier Makes 'Several Disturbing Discoveries

Massive Hole Two-Thirds the Size of Manhattan Discovered in Antarctic Glacier NASA Study Of Antarctic Glacier Makes 'Several Disturbing Discoveries
Theresa Hayes | 01 February, 2019, 20:13

West Antarctica, home to some of the fastest-flowing and fastest-melting glaciers, accounts for the bulk of the loss calculated in the new work.

A study led by the agency revealed a cavity about two-thirds the area of Manhattan and roughly 304 metres tall is growing under Thwaites Glacier in West Antarctica. That cavity is big enough to hold 14 billion tons of ice or 5.6 million Olympic-sized swimming pools.

Changes in surface height at Thwaites Glacier's grounding line.

"We have suspected for years that Thwaites was not tightly attached to the bedrock beneath it", said Eric Rignot, one of the co-authors of the study.

'Thanks to a new generation of satellites, we can finally see the detail'.

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. Researchers combined the NASA data with data from Italian and German spaceborne synthetic aperture radars. 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 growing cavity (red mass, center) caused the greatest sinking.

Once gone, surrounding glaciers will have no obstacle in their path, speeding up their melting and the potential release of enough water to raise sea levels by as much as 2.4m.

Instead, the team used airborne and satellite ice-penetrating radars to reveal the cavity.

A large hole under an Antarctic glacier is a sign of rapid decay that could lead to dramatic sea level rise, a study says.

"We are discovering different mechanisms of retreat, ' Mr Milillo said". But the research shows melt in East Antarctica-long thought to be the more stable region-has been underestimated.

"On the eastern side of the glacier, the grounding-line retreat proceeds through small channels, maybe a kilometer wide, like fingers reaching beneath the glacier to melt it from below", Milillo said. Here, the retreat rate of the ground line has doubled from about 0.4 miles (0.6 km) annually from 1992 to 2011 to 0.8 miles (1.2 km) a year from 2011 to 2017, he said.

The newly discovered cavity sits on the western side of the glacier, where the melt rate was found to be fastest. Thwaites also "backstops neighboring glaciers that would raise sea levels an additional 8 feet (2.4 meters) if all the ice were lost", they added.

These results highlight that ice-ocean interactions are more complex than previously understood. Hopefully, the upcoming global collaboration will help researchers piece together the different systems at work under and around the glacier, the researchers said.