Tipping point already reached?
Two hundred years from now, the planet could look very different. This week two landmark studies revealed that West Antarctica's ice sheet is in a state of seemingly inevitable collapse linked to climate change. The slow-motion collapse would by itself eventually lead to a rise in global levels of 3.6-4.5 meters (12-15 feet), overrunning many of the world's islands, low-lying areas, and coastal cities. The only silver lining is that scientists conservatively estimate that the collapse could take 200-1,000 years.
"There's been a lot of speculation about the stability of marine ice sheets, and many scientists suspected that this kind of behavior is under way," said Ian Joughin, a glaciologist with the University of Wisconsin, who co-authored a study in Science focusing on a key glacier in the region, Thwaites Glacier.
The team found that Thwaites Glacier is in a state of rapid retreat, which likely cannot be halted. By itself, the Thwaites Glacier would raise global sea levels by almost 2 feet; however, the Thwaites Glacier is also the stop gap to the much larger West Antarctica ice sheet. Once the Thwaites Glacier is gone, nothing will prevent the full ice sheet from melting, according to researchers, adding another 10-13 feet.
Moreover these estimates only account for Western Antarctica, and not other ice losses across the continent or in Greenland.
Joughin and his team used airborne lasers to better map the topography of the ground beneath Thwaites Glacier, giving them the most accurate view yet of how melting will occur.
But, Joughin told Climate Progress that their findings were "conservative" and "do not include all the feedbacks." While they note that the likeliest timeline given current information is 200-500 years, the team also didn't run a worst-case scenario, meaning the ice loss could occur even faster.
The Science study was complemented by other research from NASA on six glaciers in same region--including Thwaites--which came broadly to the same conclusion: the melting of the region's glaciers has passed a tipping point. This team used satellite and airborne measurements to record the melting of the glaciers since the early 1990s and better map the topography.
"The collapse of this sector of West Antarctica appears to be unstoppable," noted co-author Eric Rignot, with the University of California and NASA, whose study was published in Geophysical Research Letters. "At this point, the end appears to be inevitable."
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Iceberg image via Shutterstock.