Antarctica in trouble

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photo: David Taylor/Science Photo Library (Associated Press)

Antarctica is home 90% of the world’s fresh water, trapped in the continent’s massive ice sheet — and the stability of much of that ice is under serious threat from global warming.Two studies published in journals This week Nature will look at how climate change is changing the condition of Antarctica’s ice sheets, spelling A grim potential future for sea level rise.

first study Look at the two in Antarctica Ice sheets are affected by what happens to them ice shelf, as protective buttresses. ice shelf stretch out oceanwhile the sheets cover the land.

“Ice shelves are huge, hundreds or even thousands of meters thick chunks of ice, some as big as France,” said lead author Chad Green, a NASA postdoctoral researcher. Jet Propulsion Laboratory, in an email. “Ice shelves float on top of the ocean in hydrostatic equilibrium, so when an iceberg breaks off an ice shelf, it has no direct effect on sea level. But every time an ice shelf collapses, it gets a little bit smaller, a little weaker. “

ice shelves usually have a healthy calving cycle And able to regenerate the ice they lost. But climate change helps speed up the calving process, weakening ice shelves from below in warmer water and making it harder to replenish. To understand what this might mean for rising sea levels, Green and his colleagues researchers used satellite data to generate a series of high-resolution maps of Antarctica’s coastline over the past 25 years.

“We found that Antarctica’s ice shelves have collapsed on the edge,” Green said.In general, they Decide Since 1997, Antarctica has lost more than 14,280 square miles (37,000 square kilometers) of ice shelf area (“TThe hat is about the size of Switzerland,” Green adds). That means that the continent’s ice shelves have lost about 12 million tons over the past 25 years, About double the previous loss estimate. All of these collapses could bring bad news for the long-term stability of the continent’s ice sheets.

“Over the past 25 years, the shrinking and weakening of ice shelves has accelerated Antarctica’s giant glaciers and increased their contribution to sea level rise,” Green said. “The most pronounced effects have been observed in the Thwaites and Pine Island glaciers in West Antarctica, and there is no sign of them slowing down anytime soon.” (Thwaites glaciers are often referred to as “doomsday glaciers”, it is at considerable trouble.)

Even ice sheets once thought to be stable Showing signs of stress.one second study out this week A look at the potential fate of the extremely important ice sheet, the East Antarctic Ice Sheet, the largest of the continent’s two ice sheets ice caps and Largest freshwater reservoir on earth. Traditionally, this ice sheet is considered more protected than wEastern ice sheets – including Thwaites and Pine Island glaciers – due to less exposure to warmer waters. But if the East Antarctic ice sheet is truly threatened, it could be catastrophic news for the planet: The ice sheet holds enough water to raise sea levels by more than 170 feet (52 meters).

“We know that small mountain glaciers around the world are shrinking rapidly and contributing to sea level rise,” said lead author Chris Stokes, professor of geography at Durham University.in a say e-mail. “We also know that the larger Greenland ice sheet is also losing mass and causing sea level rise, as well as the western part of the Antarctic ice sheet. However, we know very little about what might be happening to the East Antarctic ice sheet.”

To better understand what the future of the East Antarctic Ice Sheet might look like, Stokes and his co-authors reviewed previous work on how the ice sheet has responded to past warm periods and current levels of change, adding that “based on computer simulations Some new number-crunching at MIT can predict how much this giant ice sheet might contribute to future sea level rise,” he said.

Here’s some good news: The authors say the ice sheet is likely to remain stable in the short term, and keeping warming below 2 degrees Celsius by 2100 will keep the ice sheet from collapsing in the long term. But the study also noted that the East Antarctic ice sheet is already showing signs of stress from climate change, and time is running out for action. Allowing the world to heat up beyond the reach of the Paris Agreement could mean the East Antarctic ice sheet could raise sea levels by as much as 3 to 10 feet (1 to 2 meters) by 2300, the study found.

“The key conclusion of our work is that if we can meet the Paris climate agreement, we can almost certainly avoid a significant sea level contribution from East Antarctica,” Stokes said. “So, I think with all the doomsday stories we hear, our study offers at least some hope that we have a small window of opportunity to protect this ice sheet in the coming decades. As we found in the paper Conclusion: The fate of the world’s largest ice sheet is largely in our hands.”

While the two papers deal with different situations, the message is clear: curbing warming seriously is critical to helping us stay above the water.

“Antarctica is changing. Its ice shelves are falling apart, and sea levels are rising with it,” Green said. “But as Stokes et al.. The paper says it well, there’s still time for action.”

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