Under the immense Thwaites Glacier in Antarctica there is an unexpected and huge cave. It once made 14 billion tons of ice. But in the course of only three years, it melted and flowed into the Southern Ocean.
According to a NASA study, the emptiness was caused by newly discovered "fingers" of hot water flowing into cracks in the glacier caused by growing climate change. This water then accumulated between the ice and the rock, eroding the glacier above.
"As more heat and water under the glacier, it melts faster," said the study's lead author and NASA scientist, Pietro Milillo.
And the erosion of ice in the subsurface has disturbing implications.
Not only is more ice melting than previously detected, it shows that the Thwaites glacier, 160 km wide, is not as firmly fixed to the surface of the Antarctic continent as was believed.
This means that the ice mass – the size of Florida – can break and slip into the sea, much faster than projected.
Worse, the Thwaites glacier acts as a sort of "door stop", preventing contiguous glaciers from sliding toward the sea.
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"Understanding the details of how the ocean melts this glacier is critical to projecting its impact on rising sea levels over the next few decades," says NASA scientist Eric Rignot.
The void was found by ice penetration radar and a series of satellites, which are trying to understand what is happening to Antarctica as the world warms up.
The potential impact is enormous.
Unlike much of the North Pole, a huge amount of ice from the South Pole lies on land.
Ice in the water does not affect sea level when it melts.
But the new water that flows into the sea does.
And Antarctica is a huge continent covered with ice.
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The Thwaites glacier has enough ice above sea level to raise sea levels by more than 65 cm if it melts.
Once out, the nearby glaciers will have no obstacles in their way, accelerating their melting and potentially releasing enough water to raise sea level by up to 2.4m.
"We suspected for years that Thwaites was not firmly attached to the rock bed below," said study author Rignot in a NASA statement. "Thanks to a new generation of satellites, we can finally see the detail."
As the loss of these glaciers could result in flooding of large cities such as New York, new research teams must travel to this, one of the most difficult areas to reach on Earth.
The US National Science Foundation and the British National Environmental Research Council initiated a five-year field project, The International Thwaites Glacier Collaboration. He will begin his field observations later this year.