A section of the West Antarctica ice sheet is melting so quickly that nothing can stop the glaciers in the area from melting completely into the surrounding ocean, a group of scientists from NASA and the University of California-Irvine reported in a study released today.
From observing the Amundsen Sea sector of West Antarctica for the past four decades, the scientists have concluded that the glaciers there "have passed the point of no return," said Eric Rignot, a glaciologist at U.C. Irvine and NASA's Jet Propulsion Laboratory, and lead author of the study, published in the scientific journal Geophysical Research Letters.
The study, announced in a NASA press conference Monday, noted that the glaciers and ice shelves along the Amundsen Sea (shown in the video below) already release roughly the same amount released by the entire Greenland ice sheet into the ocean every year, and contain enough ice to raise the world's sea level by about 4 feet.
The glaciers are melting much faster than scientists had previously estimated, Rignot said, a development that means forecasts for sea level rise worldwide – like those released by the Intergovernmental Panel on Climate Change earlier this year – will have to be revised upward in a significant way.
"This sector will be a major contributor to sea level rise in the decades and centuries to come," Rignot said in a NASA press release, adding that "a conservative estimate is it could take several centuries for all of the ice to flow into the sea."
To reach their conclusions, the scientists looked at three lines of evidence: the rate at which the glaciers are flowing into the ocean today, how much of each glacier currently floats on top of seawater, and the terrain of the land underneath each – how it is sloped and how much lies below sea level, which indicate how quickly a glacier moving over it can be expected to push into the ocean.
The study looked closely at what are known as "grounding lines," the point where the ice of a glacier loses contact with the land and enters the sea. Here's how NASA describes the interaction:
"Just as a grounded boat can float again on shallow water if it is made lighter, a glacier can float over an area where it used to be grounded if it becomes lighter, which it does by melting or by the thinning effects of the glacier stretching out," the release notes.
"The Antarctic glaciers studied by Rignot's group have thinned so much they are now floating above places where they used to sit solidly on land, which means their grounding lines are retreating inland."
The process of glacial melting reinforces and amplifies itself, the study notes. "As glaciers flow faster, they stretch out and thin, which reduces their weight and lifts them farther off the bedrock. As the grounding line retreats and more of the glacier becomes waterborne, there's less resistance underneath, so the flow accelerates," the NASA release points out.
So why is this happening, and what does it mean for the West Antarctica ice sheet and the world's coastal cities? Earth's warming climate – specifically, the heat that is being stored in the oceans as the world gets warmer – is partly to blame, the scientists say.
"The collapse of this sector of West Antarctica appears to be unstoppable," he said. "The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable."Follow @terrellwrites
West Antarctica Glacier Melt 'Unstoppable'
An aerial view of Antarctica's Thwaites Glacier. NASA scientists said Monday that the rapidly melting glaciers in the Amundsen Sea sector of West Antarctica 'have passed the point of no return.' (NASA)