Antarctica is melting

East Antarctica is Melting From Above and Below

Climate Central,

18 December, 2016

East Antarctica is remote even by Antarctic standards. Harsh winds and ocean currents have largely cut off the region from the rest of the world.

That’s left its massive stores of ice largely intact, especially compared to West Antarctica where a massive meltdown is underway that could raise seas by 10 or more feet in the coming centuries. But as carbon pollution warms the air andthe ocean, there are signs that the region’s stability is under threat. Two new studies of different ice shelves — tongues of ice that essentially act as bathtub plugs — have seen major melting that could portend a less stable future for the region.

The calving front of the Totten ice shelf.
Credit: Australian Antarctic Division

So first, about those ice shelves. They are indeed like bathtub plugs. Except instead of keeping water in a tub, they keep ice on the continent of Antarctica. That’s good because when it ends up melting into the ocean, it causes seas to rise. East Antarctica contains about two-thirds of all the ice in Antarctica so its stability is crucial for the world’s coastal areas.

But strange things have been happening recently. During a 2014 flyover of the Roi Baudouin ice shelf, scientists noticed a curious depression more than a mile wide in the undulating ice. When they finally investigated it in January this year, they found walls that were about 10 feet high and meltwater pouring into moulins — features that funnel surface meltwater into the heart of the ice.

The moulins were just one sign of melt happening on the surface. When scientists drilled a hole in the ice and lowered a camera, they found an otherworldly blue lake stretching more than half a mile across.

Research published in Nature Climate Change shows that the cause of these bizarre features are the powerful winds that blow down from Antarctica’s interior. Jan Lenaerts, a postdoctoral researcher at the Utrecht University in the Netherland who led the study, said that those winds helped heat the air and caused white ice to melt out, exposing a layer of dark ice beneath. That darker ice in turns absorbs more sunlight, further expediting the melt.

“Although we only found this on one ice shelf, we find the same mechanisms on many East Antarctic ice shelves,” Lenaerts said. “Given the strong response of surface meltwater production and extent of meltwater processes on the shelf to summer temperature, we can expect that in a warmer climate, these ice shelves might be vulnerable to instability that is driven by meltwater hydrofracturing.”

This on its own would be distressing news for the planet’s coastal communities. 

But there are also signs that warm water is undercutting at least one of East Antarctica’s other ice shelves. The Totten ice shelf is one of the most important ice shelves in the region. It backstops so much ice that if it were to melt, it would result in up to 12 feet of sea level rise.

Recent research has shown that its geology and interactions with the ocean mean that losing just 4.2 percent of its mass could kickstart the process to send more inland ice to the sea. And it has been melting faster than most other glaciers and ice shelves in East Antarctica.

“We knew from satellite data that the Totten has been thinning faster than other glaciers in East Antarctica, but we didn’t know why,” Steve Rintoul, the interim head of CSIRO’s Climate Science Center, said in a statement.

That’s why Rintoul and his colleagues set out to look more closely at the ice in January 2015 on the Aurora Australis, an Australian research boat. They were able to visit the calving front of the ice — where the shelf ends in the ocean — thanks to a fortuitous path that broke in the sea ice in January 2015. It’s the first time direct measurements have ever been taken by boat in the region.

Their findings from that trip, published on Friday in Science Advances, show that the bedrock underlying the ice shelf is a major driver in the melt process. They found two massive ocean channels up to 6 miles wide and a half mile deep are funneling warm water under the ice shelf and melting it out from underneath.

Taken individually, the studies are disconcerting enough. Put together, though, they paint a picture of a region that could become a much bigger player in sea level rise if carbon pollution isn’t curtailed soon.

This Melting Glacier in Antarctica Could Raise Sea Levels By 11 Feet

Motherboard,

18 December, 2016

The Earth’s climate, it seems, isn’t listening to the politicians that are insisting it’s not warming. The temperature continues to rise incrementally, and the globe’s large glaciers—giant vaults of stored water—continue to melt, releasing into the oceans. The global sea level, due to thermal expansion and glacial melting, continues to rise, building up a head of steam like a train just beginning its descent down a steep hill.

Greenland’s hulking glacier and the Arctic Sea ice are now marked by their rapid melting. And the western Antarctic ice sheet has garnered a lot of attention recently, too. But while scientists were fretting over the western side of Antarctica, the eastern Antarctic ice sheet has been melting too. Australian researchers braved treacherous sea conditions to collect data on the melting Totten Ice Shelf there, which holds up a body of ice that would cause over 11 feet of sea level rise, if it melted. Their findings are published in the journal Science Advances.

Scientists have concluded that ice shelves and glaciers in eastern Antarctica have been experiencing basal melt, where the bottom layer of a body of ice starts to melt away, but they’ve never directly observed how it’s happening and what the main drivers of melting are until now.

The Totten Ice Shelf. Image: Esmee van Wijk (CSIRO and ACE CRC)

In Antarctica, the ice sheets covering the continent are so large that they extend beyond the land’s edge. Picture a pool cover that’s only covering half of an in-ground pool. Part of it lays on the patio nearby, and the rest of it slopes downward onto the water’s surface where it floats. Where the glacier hits the water is a buttress of ice called a shelf, which keeps the land bound ice from draining into the sea. If the shelf melts then—well, you get the idea. Such is the Totten Ice Shelf.

Recovery of a mooring in heavy sea ice near the Totten Ice Shelf. Image: Steve Rintoul (CSIRO and ACE CRC)

With fair weather conducive to research, oceanographer and lead author of the study,Stephen Rich Rintoul, of the Commonwealth Scientific and Industrial Research Organization in Australia, directed a team of scientists to collect oceanographic data from the Totten ice front in east Antarctica. Previous expeditions were hampered by heavy sea ice conditions and ultimately unsuccessful. What they found was startling.

The RSV Aurora Australis at the front of the Totten Glacier. Image: Paul Brown (Australian Maritime College)

About 2,000 feet down, the team found a great trough—about 6 miles wide—worn into the side of the Totten shelf. Below 2,000 feet the gaping cavity narrows into two channels, and warm water flows through it, boring through the ice like sugar through the enamel of a tooth. The ice shelf, they measured, is melting at its base faster than all other ice shelves of similar size in East Antarctica. If it were to give way, enough ice would slide into the sea to raise global levels by over 11 feet.

Successful recovery of an oceanographic mooring near the Totten Ice Shelf. Image: Steve Rintoul (CSIRO and ACE CRC)

How the melting of these great bodies of ice will play out in the future remains to be seen, but regardless of any continuing work done to slow the effects of climate change, it’s possible the damage is already done. Giants slabs of ice that give way 10 years from now, for example, could be the product of melting that started a decade ago. Climate scientist Kerim Nisancioglu, of the University of Bergen, told the New Yorker that

“In some cases, you have, in theory, this irreversible process. You set it off and it just goes. It drains.” It’s a wait and see.

Scientists confirm that warm ocean water is melting the biggest glacier in East Antarctica

Antarctic ice melt

Western Antarctic ice sheet collapse has already begun, scientists warn

Two separate studies confirm loss of ice sheet is inevitable, and will cause up to 4m of additional sea-level rise 

The Guardian,

12 May, 2014

The collapse of the Western Antarctica ice sheet is already under way and is unstoppable, two separate teams of scientists said on Monday.

The glaciers' retreat is being driven by climate change and is already causing sea-level rise at a much faster rate than scientists had anticipated.

The loss of the entire western Antarctica ice sheet could eventually cause up to 4 metres (13ft) of sea-level rise, devastating low-lying and coastal areas around the world. But the researchers said that even though such a rise could not be stopped, it is still several centuries off, and potentially up to 1,000 years away.

The two studies, by Nasa and the University of Washington, looked at the ice sheets of western Antarctica over different periods of time.

The Nasa researchers focused on melting over the last 20 years, while the scientists at the University of Washington used computer modelling to look into the future of the western Antarctic ice sheet.

But both studies came to broadly similar conclusions – that the thinning and melting of the Antarctic ice sheet has begun and cannot be halted, even with drastic action to cut the greenhouse gas emissions that cause climate change.

They also suggest that recent accumulation of ice in Antarctica was temporary.

“A large sector of the western Antarctic ice sheet has gone into a state of irreversible retreat. It has passed the point of no return,” Eric Rignot, a glaciologist at Nasa and the University of California, Irvine, told a conference call. “This retreat will have major consequences for sea level rise worldwide.”

The two studies between them suggest sea-level rise will be far greater than envisaged by the United Nations’ IPCC report earlier this year. The IPCC forecast on sea-level rise did not factor in the melting of the western Antarctica ice sheet.

The Nasa study, to be published in Geophysical Research Letters, studied the retreat of six glaciers in western Antarctica that are already the major drivers of global sea-level rise.

One of those glaciers, Pine Island, retreated 31km at its centre from 1992-2011. Rignot said all six glaciers together contained enough ice to add an additional 1.2m (4ft) to sea levels around the world.

In the University of Washington study, which will be published in the journal Science, researchers used detailed topography maps, airborne radar and computer modelling to reach greater certainty about the projected timeline of the ice sheet collapse.

The study honed in on the Thwaites glacier – a broad glacier that is part of the Amundsen Sea. Scientists have known for years that the Thwaites glacier is the soft underbelly of the Antarctic ice sheet, and first found that it was unstable decades ago.

The University of Washington researchers said that the fast-moving Thwaites glacier could be lost in a matter of centuries. The loss of that glacier alone would raise global sea level by nearly 2ft.

Thwaites also acts as a dam that holds back the rest of the ice sheet. Once Thwaites goes, researchers said, the remaining ice in the sheet could cause another 10 to 13ft (3-4m) of global sea-level rise.

Satellite view of Antarctica with the Thwaites glacier marked in red. Photograph: UIG/Getty Images

“The thinning we are seeing is not just some temporary trend. It is really the beginning of a larger scale collapse that is likely to play out over a two to 10-century range,” Ian Joughin, a University of Washington glaciologist, told The Guardian.

He said the retreat would begin slowly, resulting in sea-level rise of less than 1mm a year for a couple of hundred years. But “then boom, it just starts to really go,” Joughin said.

Even under the worst-case scenario currently envisaged, the collapse of the entire ice sheet is about 200 years off – and the collapse could be as far away as 1,000 years, depending on future warming.

But collapse is inevitable, the scientists said. Joughin put the most likely timeframe at between 200 and 500 years.

The two teams of scientists used airborne radar and satellites to map the layers of ice down to the sea bed, and to study the rate of glacier movement. The Nasa team also drew on observations stretching back 40 years.

Even so, Rignot said he was taken aback at how fast change was occurring.

“This system, whether Greenland or Antarctica, is changing on a faster time scale than we anticipated. We are discovering that every day,” Rignot said.

Scientists are also finding that the causes of the ice loss are highly complex – and that it is not just due to warmer temperatures causing surface melting of the ice.

Both papers said the contact between the glaciers and the relatively warmer water at the ocean depths was the main driver of the slow-motion collapse.

Rignot said that even drastic action to cut greenhouse gas emissions that cause climate change could not prevent the collapse.

“We feel this is at the point where even if the ocean is not warming up, is not providing additional ocean heat, the system is in a sort of chain reaction that is unstoppable,” he told reporters on a conference call.

The only thing that could hold the glaciers back would be a large hill or big mountain that could block the retreat, Rignot said. But there is none, he said, “So we think it is not going to be stoppable.”