Ice Apocalypse


By the end of this century, the precipitous collapse of Antarctic glaciers can flood coastal cities.

In a remote region of Antarctica, known as Pine Island Bay, 2500 miles from the edge of South America, two glaciers hold a human civilization hostage.

Stretching across a frozen plain over 240 km long, these glaciers, called Pine Island and Twights, have been steadily crawling for thousands of years to the Amundsen Sea, which is part of the vast Southern Ocean. Inland, the glaciers expand into an ice reserve 3 km thick, covering the area of ​​Texas (approximately equal to the area of ​​Ukraine).

There is no doubt that this ice will melt as the Earth warms. The question of life is when.

Pine Island Bay Glaciers are two of the largest and most rapidly melting in the Antarctic. (Rolling Stone called Twights “Doomsday Glacier” earlier this year). Together they act like a dam holding enough ice to raise the level of the ocean by 3 meters — they would submerge every coastal city on the planet. For this reason, finding out how quickly these glaciers collapse is one of the most important scientific issues in the modern world.

To understand this, scientists returned to the end of the last ice age, about 11,000 years ago, when global temperatures were at about the current level. The bad news? There is growing evidence that the Pine Island Bay glaciers quickly collapsed, flooding the coastlines of the world — the result of a process called “instability of sea coastal ice.”

The ocean floor deepens in the center of this part of the Antarctic, so each new iceberg that comes off exposes ever higher cliffs. The ice becomes so heavy that these tall rocks cannot support their weight. As soon as they begin to crumble, their destruction cannot become.

“The ice is not very strong and it will collapse if these rocks reach a certain height,” explains Christine Poinard, glaciologist from the Goddard Space Flight Center at NASA. "We need to know how quickly this will happen."

Over the past few years, scientists have identified the instability of sea ice as a feedback that could initiate the disintegration of the entire ice sheet of the Western Antarctic in this century — much faster than previously thought.

Huge - the size of a skyscraper - pieces of ice rocks will fall into the sea, as tall as the Statue of Liberty, and as deep under water as the height of the Empire State Building. The result: a global catastrophe, which we have never seen.


Twits Glacier, offshore.

Ice happens in different forms, with different consequences when it melts. Floating ice, as well as covering the Arctic Ocean in winter, and including ice shelves, does not raise sea levels. (Think of melting ice in a glass).

On the other hand, ground ice is much more problematic. When it falls into the ocean, it is added to the total volume of fluid in it, raising its level.

Antarctica is a vast territory — only half the size of Africa, and the ice covering it averages over one and a half kilometers. Before the burning of fossil fuels caused global warming, the ice remained in relative equilibrium: the snowfall in the depths of the continent approximately corresponded to icebergs, which were detached from the glaciers at the edges.

Now, since carbon dioxide retains more heat in the atmosphere and warms the planet, the balance is upset.

The massive collapse of Pine Island and Twights will lead to disaster. Giant icebergs will sail from the Antarctic, like a parade of frozen soldiers. All over the world, high tides will become even higher, slowly burying every coastline on the planet, flooding coastal cities and creating hundreds of millions of climate refugees.

All this can take place in just 20-50 years - too fast for humanity to adapt.

“With the instability of sea coastal ice, sea level rise in the next century will be much greater than we thought five or ten years ago,” Poinar says.

Many of these new problems were discovered by two climatologists: Rob Deconto at the University of Massachusetts-Amherst and David Pollard at the University of Pennsylvania. The study, which they published last year, was the first to incorporate the latest understanding of sea-ice instability into the Antarctic model.

Their results showed that ocean levels could rise much higher in this century. “The Antarctic model opens up the prospect of an inevitable ice collapse,” says the headline in the scientific journal Nature.

According to Deonto and Pollard, an increase in sea level at the end of the century is two meters more likely than one. But if carbon emissions go under the worst-case scenario, all 3 meters of ice blocked in West Antarctica can be released, as their research has shown.


Pine Island Glacier, offshore.

Three feet of rising sea levels will lead to more frequent flooding of US cities such as New Orleans, Houston, New York and Miami. Countries in the Pacific, such as the Marshall Islands, will lose most of their territory. Unfortunately, now it seems that one meter is possible only in the best scenarios.

With two meters in the United States, about 12 million people will be displaced, and the most vulnerable megalopolises of the world, such as Shanghai, Mumbai and Ho Chi Minh, can be erased.

With 3 meters the land, which is currently inhabited by hundreds of millions of people around the world, will go under water. South Florida will be largely uninhabitable; Hurricane Sandy-wide floods will be about twice a month in New York and New Jersey, since the attraction of one moon will be enough to send ocean water to homes and buildings.

Deconto and Pollard made the discovery by comparing ancient sea levels on shores around the world to the current behavior of the ice cap.

About 3 million years ago, when global temperatures were about as warm as expected at the end of this century, the oceans were a couple meters higher than today.

Previous models assumed that it would take hundreds or thousands of years to raise sea levels of this magnitude. But as soon as they introduced sea ice instability, the Deconto and Pollard model pointed to a catastrophe if the world supports the “normal mode” and we do not reduce carbon dioxide emissions.

However, rapid cuts in greenhouse gas emissions have shown that Antarctica will remain almost completely untouched for hundreds of years.

Pollard and Deconto are the first to admit that their model is still raw, but its results have alarmed the entire scientific community.

“It can happen faster or slower, I don’t think we really know,” said Jeremy Bassis, a leading glaciologist at the University of Michigan. "But it is possible and very scary."

Scientists believed that ice caps respond to climate change over the millennia. After all, they are chunks of ice that are kilometers thick.

However, new evidence suggests that as soon as a certain temperature threshold is reached, the ice shelves that go into the sea, like those located near Pine Island Bay, will begin to melt from above and below, weakening the structure and accelerating the destruction, leading to instability ice shield.

In a new study published last month in the journal Nature, a team of scientists from Cambridge and Sweden points to evidence of thousands of scratches left by ancient icebergs on the ocean floor, indicating that the Pine Island glaciers were destroyed in a relatively short period of time at the end of the last ice age.

The only place in the world where glacier climate instability can be observed today is the Jacobshavn glacier in Greenland, one of the fastest-collapsing glaciers in the world. Deconto says that to build their model, they took the Jacobshavn collapse, reduced it in half to be more conservative, and then applied it to Twights and Pine Island.

But there is reason to believe that Twites and Pine Island can collapse even faster than Jacobshavn.

Now the floating ice shelf protects two glaciers and helps to contain the flow of ice into the sea. But recent examples from other regions, such as the rapidly collapsing Larsen B ice shelf on the Antarctic Peninsula, show that after the ice shelves are destroyed as a result of warming, their parent glaciers begin to flow faster to the sea, which can weaken the stability of ice further into the depths continent.

“If you remove the ice shelf, it is possible that not only instability of the coastal ice sheet will begin, but also instability of sea ice,” said Matthew Wise, a polar scientist from the University of Cambridge.

This indicates a possible rapid destabilization of the entire ice sheet of the Western Antarctic in this century. “As soon as the forces exceed the fragility of the ice,” says Wise, “it just collapses.”

And this is not only Pine Island Bay. With the current course, other glaciers around Antarctica will also be vulnerable. And also Greenland, which can bring in up to 6 meters of sea level rise.

Along with a meteor strike, the rapid rise in sea level from collapsed glaciers is one of the fastest ways our world can change. This is about as fast as climate change.

However, some scientists are not fully convinced that anxiety is justified. Ted Scambos, a lead scientist at the National Snow and Ice Data Center in Colorado, said the new research by Wise and his colleagues, who identified the instability of the ice sheet in Pine Island 11,000 years ago, is "tantalizing evidence." But he says the study does not establish how quickly this happened.

“We need to understand a lot more so that we can use this mechanism to predict how the Twights glacier and other glaciers will recede,” he says. “The question comes down to what slows down this process?”

Scambos considers it unlikely that Twights or Pine Island will collapse all at once. First, if there was a quick collapse, it would create a bunch of icebergs that could act as a temporary ice shelf, slowing down the speed of retreat.

However, despite the differences, there is a growing understanding in the scientific community that we need to do much more to determine the risk of a rapid rise in sea level. In 2015, the governments of the United States and the United Kingdom began to plan an unusual and urgent joint research program to study the Twights Glacier. Called " How much, how fast?" , It begins early next year and lasts five years.

Observing the two governments that have combined their resources “is indeed a sign of the importance of such research,” Poinar says.

Considering what is at stake, there is not enough research program in Twites, but it’s all that most researchers can get. “In reality, this is all that can be done in the next five years under the current financing conditions,” says Pollard.

He, of course, refers to the disregard of Trump's guidance to science and adequate scientific funding; the White House budget in 2018 includes the first reduction in funding for the National Science Foundation , which, as a rule, funds research in the Antarctic.

“It would be wise to make great efforts, from my point of view,” says Pollard. Engineers must examine key Antarctic glaciers as if they were analyzing a building, he says, examining the weak points and understanding how they can break down. "If you significantly expand the research now, [the cost] will still be small compared to the losses that may occur."


Pine Island Glacier.

Bassis, a scientist glaciologist from the University of Michigan, theoretically for the first time described the process of sea ice instability in studies published just a few years ago.

He is 40, but his science has already changed a lot in his career. In 2002, when Bassis conducted his postgraduate studies in another Antarctic region, he was shocked when he returned to base camp and learned that the ice shelf Larsen B had practically disappeared overnight.

“Every review of our understanding told us that ice sheets could change faster than we thought,” he says. “We did not predict that Pine Island was going to retreat, we did not predict that Larsen B was going to collapse. We look at these things after they happen. ”

All research in Antarctica has a recurring theme: we determine how fast Pine Island and Twights are melting. The rapid transition from fossil fuels over the next few decades may be enough to postpone the rise in ocean level for a couple of centuries. This decision costs countless trillions of dollars and millions of lives.

“The results,” says Bassis, “will really depend on the choices people make.”



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