A gigantic cavity confirms the disintegration of an Antarctic glacier

A gigantic 40-square-meter, 300-meter-high cavity that grows at the bottom of the Thwaites Glacier in West Antarctica confirms that this mbad of ice is disintegrating.

The findings of a new study conducted by NASA highlight the need to observe in detail the lower Antarctic glaciers in order to calculate how quickly sea level will rise in the future. response to climate change.

The researchers hoped to find spaces between the ice and the rock at the bottom of Thwaites where the ocean water could flow and melt the glacier from underneath. The size and explosive growth rate of the new hole, however, surprised them. It is large enough to hold 14 billion tonnes of ice and most of that ice has melted in the last three years.

"We have thought for years that Thwaites was not well attached to the underlying rock," said Eric Rignot of the University of California at Irvine and NASA's Jet Propulsion Laboratory (JPL). Rignot is co-author of the new study published in Science Advances.

"Thanks to a new generation of satellites, we can finally see the details," he said.

The cavity was revealed by an ice penetration radar in NASA's IceBridge operation, an air campaign launched in 2010 that studies connections between the polar regions and the global climate. The researchers also used data from a constellation of synthetic aperture radars from Italian and German spacecraft. These very high resolution data can be processed by a technique called radar interferometry to reveal the evolution of the ground surface located between the images.

"[El tamaño de] A cavity under a glacier plays an important role in melting, "said Pietro Milillo, lead author of the study, JPL. The more heat and water enter the glacier, the faster it melts ".

Speed ​​of the under-estimated thaw

Numerical models of ice caps use a fixed shape to represent a cavity under the ice, instead of allowing the cavity to change and develop. The new discovery implies that this limitation is likely to cause these models to underestimate the speed with which Thwaites loses ice.

About the size of Florida, the Thwaites Glacier is currently responsible for about 4% of the sea level rise in the world. It has enough ice to lift the global ocean by just over 2 centimeters and holds nearby glaciers that would raise the sea level by 2.4 centimeters if all the ice was lost.

Thwaites is one of the most difficult places to reach on Earth, but it is about to be better known than ever. The National Science Foundation of the United States and the National Environmental Research Council of the United Kingdom are preparing a five-year field project to answer the most critical questions about their processes and characteristics. The Thwaites Glacier International Collaboration will begin its field experiments in the southern hemisphere in the summer of 2019-20.

The huge cavity lies beneath the main glacier trunk on the west side, the farthest side of the western Antarctic Peninsula. In this region, when the tide goes up and down, the ground connection line moves back and forth over an area of ​​about 3 to 5 kilometers. The glacier has been detached from a ridge in the bedrock at a constant rate of about 0.6 to 0.8 km per year since 1992. Despite this rate of steady decline in the land line, the melting rate on this side from the glacier, it is extremely high.