Antarctic ice disappears, threatening massive sea level rise: NPR

Three new scientific analyzes of Antarctic ice loss paint a portrait of a continent in difficulty. Sea ice is disappearing, gigantic portions of the West Antarctic ice sheet are collapsing, and even relatively stable East Antarctica is showing worrying changes.

This is a problem for humanity.

Let’s start with sea ice. Every winter, the water in the oceans around Antarctica freezes. Since Antarctica is located in the Southern Hemisphere, this occurs during the North American summer months: deep winter in Antarctica is in July, August, and September.

At its most extensive, sea ice covers an area the size of Antarctica itself, doubling the size of the frozen continent.

But winter sea ice is shrinking, in part because ocean water is warmer due to climate change. And this year, there was less ice than ever before, since satellites began tracking annual ice extent around 1980.

On September 10, Antarctica’s sea ice reached its largest extent of the year, but it was much smaller than the average sea ice of decades past. In fact, it was nearly 350,000 square miles smaller than the previous record, measured in 1986, according to a recent analysis by the National Snow and Ice Data Center, a research center at the University of Colorado at Boulder, also affiliated to the federal government.

Losing sea ice is a problem for many reasons. Although it does not directly add additional water to the ocean, the absence of sea ice contributes to global sea level rise in other ways. Sea ice around Antarctica protects land glaciers and the huge ice shelves that extend into the water from storms and ocean water above freezing. Without this protection, the ice can melt more quickly, causing sea levels to rise even further.

And it’s hard for sea ice to recover after a bad year like this. Water that doesn’t freeze – exposed seawater – absorbs more heat than ice, making it more difficult for ice to reform the following year.

“There is growing evidence that the Antarctic sea ice system has entered a new regime, characterized by a much stronger influence of warm ocean waters limiting ice growth,” the scientists write from the National Snow and Ice Data Center in their analysis of this year’s record. small extent of sea ice.

Antarctica’s glaciers are also melting rapidly and humans have no choice but to adapt

New research also sounds the alarm about how Antarctica’s massive ice shelves and glaciers are responding to global warming.

The West Antarctic Ice Shelf is the part of Antarctica melting fastest in response to climate change. It contains enough water to raise sea levels by about 10 feet.

Scientists have been warning for decades that once the West Antarctic ice begins to disintegrate, it will grow in size and will be very difficult, if not impossible, to reverse within human life. A new study reveals that the process of uncontrolled melting is already underway.

The rate of ice melting and ocean warming in a crucial part of West Antarctica is three times higher than in the 20th century, according to the study published in the journal Climate change this week.

Exposed seawater absorbs more heat than ice, making it more difficult for ice to reform.

Mario Tama/Getty Images

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Mario Tama/Getty Images

And when the authors used a computer to simulate what would happen if humans immediately reduced their greenhouse gas emissions, they found that it would have virtually no effect on the rate of melting of West Antarctica for the rest of the century.

“We appear to have lost control of the melting of the West Antarctic ice shelf during the 21st century,” says Kaitlin Naughten of the British Antarctic Survey and one of the study’s authors. “Our actions today will likely make a difference later, in the 22nd century and beyond, but that’s a timescale that none of us here are likely to be around to see.”

Previous studies have reached similar conclusions, although this is the first major study simulating both ice and ocean changes in West Antarctica. The authors note that while it may be too late for emissions reductions to save large areas of ice in West Antarctica, they do not predict that the entire ice shelf West Antarctic ice will collapse over the next century. And it’s not too late to protect the even more massive East Antarctic ice sheet.

“It’s a ray of hope,” Naughten says. “West Antarctica is much smaller than East Antarctica. And we think East Antarctica is quite stable (and) will probably stay that way.”

However, a separate study published this week in the journal Scientists progress suggests that East Antarctica’s massive glaciers may also be melting faster than previously thought, as warm ocean water mixes with meltwater beneath the ice. While scientists expect East Antarctica to remain relatively stable for 100 years or more, the new discovery could also have implications for how quickly glaciers disintegrate in West Antarctica.

Overall, the new research paints a picture of a continent that is poised to cause sea levels to rise by several meters in coming decades, and which could cause a catastrophic rise in sea levels. sea ​​in the longer term if humans do not move away from fossil fuels more quickly.

“In this context, courage looks like adaptation,” says Naughten, emphasizing that reducing emissions alone is not enough. “If we can plan ahead to reduce human suffering and save human lives, it’s better than turning a blind eye until the ocean is at our doorstep.”

Some U.S. cities are already beginning to prepare for several feet of sea level rise this century, in part because the National Oceanic and Atmospheric Administration’s official sea level rise forecasts are already holding up. account of some melting of Antarctica. Loss of ice in West Antarctica disproportionately causes sea level rise on the U.S. East and Gulf coasts, due to ocean currents and other ocean and glacial dynamics.