A huge swath of the West Antarctic ice sheet has “passed the point of no return,” a pair of new science reports say, melting far faster than expected in an “irreversible decline” that will raise the world’s oceans by anywhere from 4 to 10 feet.
“This sector will be a major contributor to sea level rise in the decades and centuries to come,” said glaciologist Eric Rignot, a professor at the University California, Irvine and a senior scientist at NASA’s Jet Propulsion Laboratory.
How soon? "Within a century or the next one," Rignot adds in a call with U.S. News. "The studies are very conservative, two to nine centuries, but keep in mind that the numerical models that I used to make these predictions underpredict what's really happening. I think it will happen much sooner."
In fact, the ice is melting so rapidly that it’s fallen into a recurring loop: As glaciers move faster toward the water, they stretch out and become thinner, which then decreases their weight and lifts them off the bedrock, allowing more of the glacier to become waterborne, which in turn accelerates the melting further.
Indeed, the melting of the West Antarctic ice sheet, which spans about 2.5 million square kilometers, Rignot says, has come not from warm air above, but instead from warm
water rising from the ocean depths below. The water itself is naturally warm,
but it’s being pulled up toward the ice sheet by intensifying winds around the
Those winds may have something to do with natural variability in the climate, scientists say, but they’re also likely the result of global warming caused by human emission of greenhouse gases, as well as perhaps the ozone hole over the Antarctic, which opened after the prolonged release of ozone-destroying gases, like aerosol.
"The collapse of this sector of West Antarctica appears to be unstoppable," Rignot said in a statement. "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."
Rignot’s findings, published in the journal Geophysical Research Letters, were the more conservative of the two reports released Monday. Culling 40 years of satellite data and other observations, he and his team projected that the glaciers will cause seas to rise by about 4 feet.
The other study, carried out by researchers at the University of Washington, used computer models to estimate the glaciers’ melting. It found that the oceans may rise by as much as 10 feet, but perhaps in a longer time frame: 200 to 1,000 years from now, as opposed to within the next few decades or next century. It was published in the journal Science.
Both studies were released one week after the National Climate Assessment, an analysis of how global warming is affecting the United States, found that the changing climate will likely contribute significantly to sea level rise.