Antarctic ice is disappearing, threatening massive sea-level rise: NPR

A trio of new scientific analyzes of ice loss in Antarctica paint a picture of a continent in trouble. Sea ice is disappearing, vast swathes of the West Antarctic ice sheet are collapsing and even relatively stable East Antarctica is showing alarming changes.

This is a problem for mankind.

Let’s start with sea ice. Every winter, the sea water around Antarctica freezes. Since Antarctica is in the Southern Hemisphere, this happens during the North American summer months – Antarctica’s deepest winters are July, August and September.

At its widest, sea ice covers an area roughly the size of Antarctica, doubling the size of the frozen continent.

But winter sea ice is shrinking because ocean waters are warming due to climate change. There was less snow this year than in 1980 when satellites began tracking annual snow levels.

On September 10, Antarctica’s sea ice reached its largest extent of the year, but it was much smaller than the average sea ice extent in past decades. In fact, it was almost 350,000 square miles smaller than the previous record small size measured in 1986. Analysis Through the National Snow and Ice Data Center, a research center at the University of Colorado, Boulder that is affiliated with the federal government.

Sea ice disappearance is a problem for several reasons. Although it doesn’t directly add additional water to the oceans, missing sea ice contributes to global sea level rise in other ways. The sea ice around Antarctica protects the glaciers on land and the massive ice shelves that extend into the water from storms and super-freezing seawater. Without that protection, that ice would melt faster, and that would lead to sea level rise.

And it’s hard for sea ice to recover after a bad year like this. Unfrozen water—exposed ocean water—absorbs more heat than ice, making it harder for ice to form again the following year.

“There is growing evidence that the Antarctic sea ice system has entered a new regime, one with a much stronger influence of warm ocean water, which limits ice growth,” scientists at the National Ice and Snow Data Center write in an analysis of this year’s record breaking record. Low sea ice extent.

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

The new research also raises alarm about how Antarctica’s enormous ice shelves and glaciers are responding to a warming world.

The West Antarctic Ice Sheet is the part of Antarctica that is melting most rapidly in response to climate change. That’s enough water to raise global sea levels by about 10 feet.

They have warned for decades that once the ice sheet in West Antarctica begins to melt, it will accelerate and reverse within a human lifetime will be very difficult, if not impossible. A new study finds that the process of runway melting is already underway.

The rate of ice melting and ocean warming in a critical region of West Antarctica is three times higher than it was in the 20th century. study Published in the magazine Natural climate change This week.

Exposed ocean water absorbs more heat than ice, making it harder for ice to re-form.

Mario Tama/Getty Images

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When the authors used computers to simulate what would happen if humans immediately reduced greenhouse gas emissions, they found that it would have essentially no effect on the rate of melting in West Antarctica.

“It appears that we may have lost control of the melting of the West Antarctic ice sheet in the 21st century,” says Caitlin Naughton of the British Antarctic Survey and one of the authors of the study. “Our actions today will still make a difference in the 22nd century and beyond, but this is a time frame none of us here can see.”

previous studies Although this is the first large-scale study to simulate both ice and ocean changes in West Antarctica, they have come to similar conclusions. Although emissions reductions may be too late to save large areas of ice in West Antarctica, the authors note that they do not predict that the entire West Antarctica ice sheet will collapse in the next century. And it’s not too late to protect the vast East Antarctic ice sheet.

“It’s a glimmer of hope,” Naughten says. “West Antarctica is much smaller than East Antarctica. We think East Antarctica is more stable. [and] Likely to remain so.”

However, A A separate study Published this week in the magazine Scientific advances This suggests that massive glaciers in East Antarctica may be melting faster than previously thought, as warm ocean water mixes with meltwater under the ice sheet. While scientists expect East Antarctica to remain relatively stable for 100 years or more, the new discovery could also have implications for how quickly the ice caps in West Antarctica are disintegrating.

Taken together, the new research paints a picture of a continent where sea levels will rise by several feet in the coming decades, and sea level rise will be catastrophic in the long term unless humans rapidly transition away from fossil fuels.

“In this environment, courage looks like adaptation,” says Naughten, adding that reducing emissions isn’t enough by itself. “If we can plan ahead to reduce human suffering and save human lives, it is better than turning a blind eye until the ocean arrives at our doorstep.”

Some U.S. cities are already bracing for several feet of sea-level rise this century, as official sea-level rise projections from the National Oceanic and Atmospheric Administration already factor in some Antarctic melting. A disappearing ice sheet in West Antarctica Proportionately triggers sea level rise On the East and Gulf coasts of the United States, due to ocean currents and other ocean and ice dynamics.