NASA: The Collapse Of The West Antarctic Ice Sheet Is ‘Unstoppable’
Melting of the West Antarctic ice sheet is likely unstoppable, two new papers published Monday indicate. That means the sea level rise projects by 2100 will need to be revised, closer to 3 feet of sea level rise.
We’ve basically uncorked the bottle, and this ice is flooding into the water, raising sea level. It will likely take centuries to fully collapse, though.
While it’s smaller than the East Antarctic ice sheet, the West Antarctic ice sheet is particularly vulnerable to melting from warm ocean waters because it sits on top of bedrock below sea level, NASA said. If it melts completely, it could add 13 feet of water to sea level.
According to study researcher Eric Rignot, of NASA’s Jet Propulsion Laboratory and the University of California, Irvine, the glaciers in the Amundsen Sea sector of West Antarctica “have passed the point of no return.”
A second paper deems the collapse of the Thwaites Glacier Basin “inevitable” and which by itself will raise sea level by nearly 2 feet in the next few centuries.
We’ve already been seeing this melt in the form of elevation changes in the glaciers during the past few decades:
Unstable ice and rising seas
The first study, “Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011,” was just accepted for publication in the journal Geophysical Research Letters.
It uses 40 years of observations to determine the movement of West Antarctica’s glacial “grounding lines” — “the critical boundary between grounded ice and the ocean which delineates where ice detaches from the bed and becomes afloat and frictionless at its base,” according to the study.
This ground line has been moving steadily south, the researchers note. That’s because of a positive feedback loop created as relatively warmer sea water digs deeper caverns underneath the ice, further pushing back the grounding line, seen in the GIF below.
Movement of this line means potentially more ice breaking off and entering the ocean, which raises sea level.
The paper concludes: “We find no major bed obstacle upstream of the 2011 grounding lines that would prevent further retreat of the grounding lines farther south. We conclude that this sector of West Antarctica is undergoing a marine ice sheet instability that will significantly contribute to sea level rise in decades to come.”
Monday’s predictions of sea level rise don’t include these impacts. In a press release from NASA they note:
These glaciers already contribute significantly to sea level rise, releasing almost as much ice into the ocean annually as the entire Greenland Ice Sheet. They contain enough ice to raise global sea level by 4 feet (1.2 meters) and are melting faster than most scientists had expected. Rignot said these findings will require an upward revision to current predictions of sea level rise.
Although the Amundsen Sea region is only a fraction of the whole West Antarctic Ice Sheet, the region contains enough ice to raise global sea levels by 4 feet (1.2 meters).
This is a high-resolution map of Thwaites Glacier’s thinning ice shelf. Warm circumpolar deep water is melting the underside of this floating shelf, leading to an ongoing speedup of Thwaites Glacier. This glacier now appears to be in the early stages of collapse, with full collapse potentially occurring within a few centuries. Collapse of this glacier would raise global sea level by several tens of centimeters, with a total rise by up to a few meters if it causes a broader collapse of the West Antarctic Ice Sheet.
Thwaites Glacier Basin on the verge of collapse
A related paper discussing the instability of the West Antarctic ice sheet — titled “Marine Ice Sheet Collapse Potentially Underway for the Thwaites Glacier Basin, West Antarctica” — will be published this week in the journal Science.
It analyzes specific details on the collapse of the Thwaites Glacier Basin and uses models to determine how long it will be until it disappears completely.
Results show that as the ice edge retreats into the deeper part of the bay, the ice face will become steeper and, like a towering pile of sand, the fluid glacier will become less stable and collapse out toward the sea.
“Once it really gets past this shallow part, it’s going to start to lose ice very rapidly,” study researcher Ian Joughin, of the University of Washington, said in a press release.
The fast-moving Thwaites Glacier will likely disappear in a matter of centuries, researchers say, raising sea level by nearly 2 feet. That glacier also acts as a linchpin on the rest of the ice sheet, which contains enough ice to cause another 10 to 13 feet (3 to 4 meters) of global sea level rise.
While collapse seems inevitable, we have at least 200 years before it happens.
New sea level predictions
With these new findings, the Intergovernmental Panel On Climate Change (IPCC) report sea level rise predictions “will almost certainly be revised and revised upwards,” Sridhar Anandakrishnan, a researcher at Pennsylvania State University who was not involved in the new studies, said at the press conference.
“IPCC numbers are, by their very nature, on the conservative side,” he said. They depend on consensus from past studies and models. The current IPCC sea level rise numbers “don’t really include Antarctic contributions to any great measure,” he said, because strong data had not been available until now.
It’s likely these predictions will be around the higher levels of previous IPCC reports. Perhaps up to 3 feet of sea level rise by 2100.