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Antarctica is in trouble

Antarctica is in trouble
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photo: David Taylor/Science Photo Library (AP)

Antarctica is home to 90% of the world’s fresh water, trapped within the continent’s massive ice sheets – and the stability of much of this ice is seriously threatened by global warming. Two studies published in the journal This week’s Nature takes a look at how climate change is rocking conditions in ice sheets in Antarctica, spelling the bleak potential future of sea level rise.

The first to learn looks like Antarctica two Ice sheets are affected by what is happening to them ice shelves, what serves as protective buttresses. ice shelves overstretch the oceanwhile the leaves cover the land.

“Ice shelves are huge pieces of ice, hundreds or even thousands of meters thick, and some of them are as big as France,” said lead author Chad Greene, a NASA postdoctoral researcher Jet Propulsion Laboratory, in an email. “Ice shelves float on the ocean in hydrostatic equilibrium. So when an iceberg breaks off an ice shelf, it has no direct impact on sea levels. But when an ice shelf calves, it gets a little smaller and a little weaker.”

Ice cream shelves usually have a healthy calving cycle and can regenerate the lost ice. But climate change has helped speed up the calving process, weakening the ice shelves from below in warming water and making it harder for the ice shelves to replenish themselves. To understand what this could mean for sea-level rise, Greene and his research colleagues used satellite data to create a series of high-resolution maps of the Antarctic coast over the past 25 years.

“What we found is that Antarctica’s ice shelves have disintegrated at the edges,” Greene said. Overall they definitely that Antarctica has lost more than 14,280 square miles (37,000 square kilometers) of ice shelf area since 1997 (“Tabout the size of Switzerland,” Greene added). That means that the continent’s ice shelves have lost about 12 million tons in the last 25 years, roughly double previous loss estimates. All of this crumbling could mean bad news for the long-term stability of the continent’s ice sheets.

“Over the past quarter century, the shrinking and weakening of the ice shelves has allowed Antarctica’s massive glaciers to grow faster and increase their contribution to sea-level rise,” Greene said. “The greatest impacts have been observed at Thwaites and Pine Island glaciers in West Antarctica, and there is no evidence that either will slow down any time soon.” (Thwaites Glacier is commonly referred to as the ‘doomsday glacier.’ and it’s in pretty big trouble.)

Even ice sheets once thought to be stable show signs of stress. One second to learn out this week looks at the possible fate of an incredibly important ice sheet – the East Antarctic Ice Sheet, the largest of the two continents ice sheets and the largest freshwater reservoir on earth. This ice sheet is traditionally considered more sheltered than the weastern ice sheet – which includes Thwaites and Pine Island glaciers – due to less exposure to the warming ocean waters. But if the East Antarctic Ice Sheet is ever threatened, it will be potentially catastrophic news for the planet: The ice sheet contains enough water to raise sea levels by more than 52 meters.

“We know that small mountain glaciers around the world are shrinking rapidly and are contributing to sea-level rise,” says Chris Stokes, the study’s lead author and professor of geography at Durham Universitysaid in one E-mail. “We also know that the much larger Greenland ice sheet is also losing mass and contributing to sea level rise, as is the western part of the Antarctic ice sheet. However, we know much less about what might happen to the East Antarctic Ice Sheet.”

To get a better sense of 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 spells and the current magnitude of change, adding “A little new number crunching based on computer simulations predicting how much this huge ice sheet could 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 warming below 2 degrees Celsius by 2100 will keep the ice sheet from collapsing in the long term. But the study also notes that the East Antarctic Ice Sheet is already showing signs of stress from climate change and that time to act is running out. Allowing the world to warm beyond the Paris Accord limits, the study says, could mean that the East Antarctic ice sheet could raise sea levels by as much as 1 to 2 meters by 2300.

“The key takeaway from our work is that if we can meet the Paris Climate Agreement, we can almost certainly avoid a major sea level contribution from East Antarctica,” Stokes said. “So I think that among all the doomsday stories we hear about, our study offers at least some hope that we have a small window of opportunity to protect this ice sheet in the next few decades. As we conclude in the paper, the fate of the world’s largest ice sheet rests entirely in our hands.”

Although these two papers address different scenarios, the message is clear: serious containment of warming is critical to helping us stay afloat.

“Antarctica is changing. Its ice shelves are breaking apart and sea levels are rising in response,” Greene said. “But as Stokes et al. Paper put it so well, there is still time to act.”

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