Chris Mooney, WaPo: Earth Is 'Missing' at Least 20 Ft of Sea Level Rise. Antarctica Could Be The Time Bomb

by Chris Mooney, The Washington Post, February 12, 2019

Some 115,000 years ago, Homo sapiens were still living in bands of hunter gatherers, largely confined to Africa. We still shared the globe with the Neanderthals, although it's not clear we had met them yet.

And though these various hominids didn't know it, the Earth was coming to the end of a major warm period. It was one that's quite close to our current climate, but with one major discrepancy - seas at the time were 20 to 30 feet (6 to 9 metres) higher.

During this ancient period, sometimes called the Eemian, the oceans were about as warm as they are today.

And last month, intriguing new research emerged suggesting that Northern Hemisphere glaciers have already retreated just as far as they did in the Eemian, driven by dramatic warming in Arctic regions.

The finding arose when a team of researchers working on Baffin Island, in northeastern Canada, sampled the remains of ancient plants that had emerged from beneath fast-retreating mountain glaciers.

And they found that the plants were very old indeed, and had probably last grown in these spots some 115,000 years ago.

That's the last time the areas were actually not covered by ice, the scientists believe.

"It's very hard to come up with any other explanation, except that at least in that one area where we're working ... the last century is as warm as any century in the last 115,000 years," said Gifford Miller, a geologist at the University of Colorado in Boulder who led the research on Baffin Island.

But if Miller is right, there's a big problem. We have geological records of sea levels from the Eemian. And the oceans, scientists believe, were 20 to 30 feet (6 to 9 metres) higher.

Some extra water likely came from Greenland, whose ice currently contains over 20 feet (6 metres) of potential sea level rise. But it couldn't have been just Greenland, because that entire ice sheet did not melt at the time.

That's why researchers also suspect a collapse of the most vulnerable part of Antarctica, the West Antarctic ice sheet. This region could easily supply another 10 feet (3 metres) of sea level rise, or more.

"There's no way to get tens of meters of sea level rise without getting tens of meters of sea level rise from Antarctica," said Rob DeConto, an Antarctic expert at the University of Massachusetts.

Trying to understand how Antarctica will fall

Scientists are now intensely debating precisely which processes could have played out then — and how soon they'll play out again. After all, West Antarctica has already been shown, once again, to be beginning a retreat.

Some researchers, including DeConto, think they have found a key process - called marine ice cliff collapse - that can release a lot of sea level rise from West Antarctica in a hurry.

But they're being challenged by another group, whose members suspect the changes in the past were slow - and will be again.

To understand the dispute, consider the vulnerable setting of West Antarctica itself.

Essentially, it's an enormous block of ice mostly submerged in very cold water. Its glaciers sit up against the ocean in all directions, and toward the center of the ice sheet, the seafloor slopes rapidly downward, even as the surface of the ice sheet itself grows much thicker, as much as two miles thick in total.

As much as a mile and a half of that ice rests below the sea level, but there is still plenty of ice above it, too.

So if the gateway glaciers start to move backward - particularly a glacier named Thwaites, by far the largest of them - the ocean would quickly have access to much thicker ice.

The idea is that during the Eemian, this whole area was not a block of ice at all, but an unnamed sea. Somehow, the ocean got in, toppling the outer glacial defenses, and gradually setting all of West Antarctica afloat and on course to melting.

DeConto, with his colleague David Pollard, built a model that looked to the Eemian, and another ancient warm period called the Pliocene, to try to understand how this could happen.

In particular, they included two processes that can remove glaciers. One, dubbed 'marine ice sheet instability,' describes a situation in which a partially submerged glacier gets deeper and thicker as you move toward its center.

In this configuration, warm water can cause a glacier to move backward and downhill, exposing ever thicker ice to the ocean - and thicker ice flows outward faster.

So the loss feeds upon itself.

Marine ice sheet instability is probably underway already in West Antarctica, but in the model, it wasn't enough. DeConto and Pollard also added another process that they say is currently playing out in Greenland, at a large glacier called Jakobshavn.

Jakobshavn is moving backward down an undersea hill slope, just in the way that it is feared the much larger Thwaites will drift. But Jakobshavn is also doing something else. It is constantly breaking off thick pieces at its front, almost like a loaf of bread, dropping slice after slice.

That's because Jakobshavn no longer has an ice shelf, a floating extension that used to grow out over the ocean at the front of the glacier and stabilize it. The shelf collapsed as Greenland warmed in the past two decades.

As a result, Jakobshavn now presents a steep vertical front to the sea. Most of the glacier's ice is under the water, but more than 100 meters (330 feet) extend above it - and for DeConto and Pollard, that's the problem. That's too much to be sustained.

Ice is not steel. It breaks. And breaks. And breaks.

This additional process, called 'marine ice cliff collapse,' causes an utter disaster if you apply it to Thwaites. If Thwaites someday loses its own ice shelf and exposes a vertical front to the ocean, you would have ice cliffs hundreds of meters above the surface of the water.

DeConto and Pollard say that such cliffs would continually fall into the sea. And when they added this computation, it not only recreated Eemian sea level rise, it greatly increased their projection of how much ice Antarctica could yield in this century - more than three feet.

Since there are other drivers of sea level rise, like Greenland, this meant that we could see as much as six feet in total in this century, roughly double prior projections. And in the next century, the ice loss would get even worse.

"What we pointed out was, if the kind of calving that we see in Greenland today were to start turning on in analogous settings in Antarctica, then Antarctica has way thicker ice, it's a way bigger ice sheet, the consequences would be potentially really monumental for sea level rise," DeConto said.

Moreover, the process, he argues, is essential to understanding the past - and thus how we could replicate it.

"We cannot recreate six meters of sea level rise early in the Eemian without accounting for some brittle fracture in the ice sheet model," said DeConto.

A massive debate over marine ice cliffs

Tamsin Edwards is not convinced. A glaciologist at Kings College London, she is lead author - with a number of other Antarctic experts - of a study published Wednesday in Nature (the same journal that published DeConto and Pollard in 2016) that disputes their model, in great detail.

Using a statistical technique to examine the results, Edwards and her collaborators find that the toppling of ice cliffs is not necessary to reproduce past warm periods after all.

They also present lower sea level rise possibilities from Antarctica in this century. If they're right, the worst case is back down to about 40 centimeters, or a little over a foot, rather than three to four feet.

"Things may not be as absolutely terrible as that last study predicted," Edwards said. "But they're still bad."

It is a new science, she said, and without more modeling it's unclear how ice cliffs will ultimately affect sea level rise.

But then what happened in the Eemian? Edwards thinks it just took a long time to lose West Antarctica. That it wasn't fast. After all, the entire geologic period was thousands of years long.

"We're an impatient lot, humans, and the ice sheets don't respond in a decade, they're slow beasts," she said.

DeConto says he's learned something from the critique.

"The Edwards study does illustrate the need for more in-depth statistics than we originally applied to our 2016 model output, but the models are evolving rapidly and they have already changed considerably since 2016," he said in a written statement.

But he's not backing down on marine ice cliffs. The new critique, DeConto said, implies that "these processes aren't important for future sea level rise. And I think to me, that's kind of a dangerous message."

He certainly has his allies. Richard Alley, a well known glaciologist at Penn State University who has published with DeConto and Pollard, wrote in an email that "cliff retreat is not some strange and unexpected physical process; it is happening now in some places, has happened in the past, and is expected wherever sufficiently high temperatures occur in ocean or air around ice flowing into the ocean."

The Eemian - but worse?

There's one important thing to consider - the Eemian occurred without humans emitting lots of greenhouse gases.

Atmospheric carbon dioxide was far lower than it is today. The event was instead driven by changes in the Earth's orbit around the sun, leading to more sunlight falling on the northern hemisphere.

The big difference, this time around, is that humans are heating things up far faster than what is believed to have happened in the geologic past.

And that makes a key difference, said Ted Scambos, an Antarctic researcher who is leading the US side of an international multimillion dollar mission to study Thwaites Glacier, and who is a senior researcher at the National Snow and Ice Data Center in Colorado.

"The current pace of climate change is very fast," Scambos said, and the rate of warming might cause glaciers to behave differently than they did in the past.

Accordingly, Scambos says he sees the current debate as fruitful - "it's the discussion that needs to happen" - but that it doesn't lessen his worry about the fate of Thwaites Glacier if it retreats far enough.

"There's no model that says the glacier won't accelerate if it gets into those conditions," said Scambos. "It just has to."

Humans were nowhere near the Antarctic in the Eemian - and we have never, in the modern period, seen a glacier as big as Thwaites retreat. It's possible something is going to happen that we don't have any precedent or predictions for.

Just last week, for instance, scientists reported a large cavity opening beneath one part of the glacier - something they said models could not have predicted.

There is a massive stake involved now in at least trying to figure out what could happen - before it actually does. It will help determine whether humans, now organized and industrialized and masters of fossil fuels, are poised to drive a repeat of our own geological history.

2019 © The Washington Post

https://www.sciencealert.com/earth-s-climate-s-now-like-115-000-years-ago-when-the-sea-was-much-higher

WaPo: So much water pulsed through a melting glacier that it warped the Earth’s crust

by Chris Mooney, The Washington Post, May 25, 2017

Rink Glacier on Greenland’s west coast. (NASA/John Sonntag)

NASA scientists detected a pulse of melting  ice and water traveling through a major glacier in Greenland that was so big that it warped the solid Earth — a surge equivalent in mass to 18,000 Empire State Buildings.

The pulse — which occurred during the 2012 record melt year — traveled nearly 15 miles through the Rink Glacier in western Greenland over four months before reaching the sea, the researchers said.

“It’s a gigantic mass,” said Eric Larour, one of the study’s authors and a researcher at NASA’s Jet Propulsion Laboratory. “It is able to bend the bedrock around it.”

Such a “wave” has never before been detected in a Greenland or Antarctic glacier. The total amount of mass carried in the wave — in the form of either water, ice or some combination of both — was 1.67 billion tons per month, or 6.68 billion tons over four months, according to the study, which was published in Geophysical Research Letters.

The study was led by the lab’s Surendra Adhikari and co-authored by Erik Ivins.

“These solitary waves, they’re fairly well known in rivers,” said Ivins, also a researcher at the Jet Propulsion Laboratory. “Rivers can have inundations upstream where a lot of water is collected, and the water gets bunched up as it’s going downstream and doesn’t ever really flatten out. It just remains as this wave and continues down a river.”

However, the scientists don’t know what the wave actually looked like or precisely what caused it — much of it was occurring below the surface of the glacier. They also don’t know precisely what it was made of. “We are losing a combination of water and ice. We don’t know what fraction,” said Adhikari.

The researchers were able to detect the wave only because a GPS sensor, located in a rocky inland area a little over 12 miles, moved 15 millimeters as the wave went by, pushing down on the Earth’s crust and causing a deep indentation.

“The GPS can sense that,” Larour explained.

Richard Alley, a glaciologist at Penn State University who was not involved in the study, explained it this way:

“Find a bed,” Alley said by email. “Put a little piece of tape on the sheet.  Put your fist right next to the tape and push down, while watching the tape.  The tape will move down as you push down, and also will move horizontally toward your fist just a little. Put your fist farther away, and the tape won’t move as much.  Push harder, and it will move more. While pushing down, slide your fist past the tape, and you’ll see a pattern of vertical and horizontal motions of the tape.”

“A bed isn’t exactly the elastic Earth, but that’s sort of what this team did,” Alley continued. “They saw a ‘fist’ of mass sliding down the glacier past their GPS station, caused by extra meltwater.”

Adhikari provided this animation showing the direction of the GPS device’s movement (and therefore that of the bedrock or solid Earth) as the bulk of mass went by:

An animation showing horizontal bedrock motion in response to a nearby glacier mass change in the form of a wave. Ice mass change is portrayed by ice thinning/thickening (delta H), the centroid or fulcrum of mass anomaly is denoted by the star, and the direction of bedrock motion is represented by the arrow as measured at a GPS station (circle). As the glacier gains (loses) mass, the bedrock moves toward (away from) it. (NASA-JPL/Caltech)

The wave occurred in the wake of a 2012 summer melting event that saw most of the surface of Greenland become covered with liquid water, and that still has not been surpassed by subsequent warm years.  The researchers suspect that some of that meltwater flooded beneath the ice sheet and then pulsed outward through Rink Glacier.

“It’s really related to the deep interior of Greenland that’s full of melt, and it’s trying to get rid of that melt through gravitational processes,” said Ivins.

The study also documented another, smaller “wave” at Rink Glacier in 2010, another major melt year.

Rink is far from the largest glacier in Greenland. It is about 3.4 miles wide at its front where it touches the ocean and a little over half a mile deep in the same location. Researchers have also shown that pulses of meltwater flow out from beneath the glacier in colorful silt-filled plumes, presumably through subterranean channels, which could be how some of this mass exited to the ocean in 2012.

The scale of the pulse, 6.68 billion tons, or gigatons, is still only a fraction of what Greenland contributes to the ocean every year in the form of water and ice. NASA has estimated that Greenland loses 287 billion tons annually at present (though it lost far more than that in the banner melt year of 2012).

Still, the research gives a sense of the tremendous magnitude of the changes occurring on Greenland, which is covered by enough ice to raise sea levels by over 20 feet if it were all to slide into the ocean.

And it pairs with other studies showing that the breaking off of large pieces from Greenland glaciers causes major earthquakes and that enormous lakes atop the Greenland ice sheet can vanish within hours into its depths.

The study also raises questions about whether more huge ice and water pulses will be seen as the Arctic continues to warm and Greenland to melt — and thus whether this is how a melting ice sheet exports its mass to the ocean.

But mostly, it’s just staggering to contemplate.

If the analogy of 18,000 Empire State Buildings isn’t striking enough, the researchers offered another: The mass loss through Rink Glacier from the wave, they say, was equivalent to “150 million fully loaded 18-wheelers.”

https://www.washingtonpost.com/news/energy-environment/wp/2017/05/25/so-much-water-pulsed-through-a-melting-glacier-that-it-warped-the-earths-crust/

WaPo: Scientists find more reasons that Greenland will melt faster

by Chris Mooney, The Washington Post, April 30, 2016

Photograph of Torsukatat Avannarleq, a tidewater glacier in West Greenland, with two visible sediment plumes at its terminus. These plumes are made up of glacier meltwater that has traveled under the glacier, gathering eroded material, and buoyantly floated to the surface after entering the ocean. This photograph was taken in July 2014 by Adam LeWinter, US Army Corps of Engineers, Cold Regions Research and Engineering Laboratory.

So much about the planet’s future will depend on processes that humans today cannot directly observe — because they are occurring hundreds of meters below the sea surface where enormous marine glaciers, in Greenland and Antarctica, simultaneously touch the ocean and the seafloor.

The more we learn about this crucial yet inscrutable place, the more worrying it seems.

The latest exhibit: New research out of Greenland conducted by Dartmouth earth sciences Ph.D. student Kristin Schild and two university colleagues — work that has just been published in the Annals of Glaciology. The study examined the 5.5-kilometer-wide Rink Glacier of West Greenland, with particular focus on how meltwater on the ice sheet’s surface actually finds its way underneath Rink, pours out in the key undersea area described above and speeds up the glacier’s melt.

It’s a feedback process that, if it plays out across many other similarly situated glaciers, could greatly worsen Greenland’s overall ice loss. “These big tidewater outlet glaciers are the ones that are contributing these huge icebergs, they’re the ones that have rapidly, rapidly sped up in the last decade,” Schild said. This makes it critically important to learn “what are the main factors…that are leading to all these fast changes,” she added.

Greenland is an enormous sheet of ice, capable of raising sea levels by some 20 feet if it were somehow to melt entirely and its waters were to pour into the ocean. Fortunately, it can’t just do that all of a sudden — the vast ice sheet only reaches the ocean at relatively narrow, finger-like glaciers that stretch out into fjords, or underwater canyons that lead out to the sea.

There are nearly 200 of these large outlet glaciers overall — and as Greenland goes, Rink is fairly large in size but far from the largest. It’s less than 1 kilometer tall as it extends from the seafloor deep in a west Greenland fjord up above the surface of the water, Schild said.

That’s hardly as massive as the nearby Jakobshavn Glacier, which has a base submerged well over a kilometer below sea level — and which is sending ice out into the ocean faster than any other in Greenland. But Rink, like Jakobshavn, touches the ocean across a wide, icy front, and is grounded deep below the surface of the fjord’s waters. Here is where all the action is — including spectacular calving events, in which enormous icebergs break off, tumble into the water and eventually float out of the fjords.

There’s growing concern that warming ocean waters are snaking into these fjords at depth and lapping at the glacier bases, making such breakups more likely. It doesn’t help matters that scientists studiously mapping the fjords are finding, over and over again, that they’re deeper than previously believed, creating more opportunities for the warm ocean to trigger melting.

But the situation is even more dynamic: Amid warmer atmospheric temperatures, Greenland is also melting on its surface, a process that forms vanishing lakes, ice-banked rivers and downward channels, called moulins, that carry meltwater deep beneath the ice sheet. This water then makes its way to the bases of outlet glaciers and, after traveling through complex passageways and, perhaps, being held up or stored in icy caverns, eventually flows out from beneath them and enters the sea.

It’s the net consequence of all of these processes that will ultimately govern how quickly Greenland loses mass and causes the seas to rise. And that’s what the new study gets at: It attempts to measure the mysterious process by which Greenland’s surface meltwater eventually makes its way beneath the ice sheet and then out into fjords, by flowing to glacier fronts and escaping from underneath them.

To do so, the Dartmouth researchers used satellite imagery, as well as time lapse photography, to observe the seafront in the fjord where water touches Rink Glacier. They were searching for what they call “sediment plumes”: When water rushes out from the glacier base and into the fjord, it’s filled with sediments from the bedrock below. These pulses of water then ascend hundreds of meters to the surface and create an often colorful emergence there, as you can see in the NASA image below:

The image above, acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on September 9, 2014, shows sediment plumes from meltwater exiting glaciers in southwest Greenland. (NASA Earth Observatory image by Jesse Allen, using data from the Level 1 and Atmospheres Active Distribution System (LAADS).)

The study resulted in three separate new findings about how meltwater from Greenland’s surface is making its way under Rink Glacier and speeding its ice loss — each of which suggests that not only Rink, but other glaciers like it, could lose their ice faster than previously thought.

First of all, the satellite and time-lapse images revealed that meltwater is pouring out from beneath Rink Glacier in not just one but four separate locations. That’s bad news, because it means more overall melting of the glacier is possible. “Previously that has not been observed, to have more than one ocean location for a plume,” Schild said.

Each individual plume could be causing additional melting, Schild said. Here’s how it works: As the cold, fresh water rushes out from beneath the glacier, it cascades into ocean water that is saltier and warmer. So the cold water, being lighter, rises toward the surface hundreds of meters away — pulling the salty, warm water inward to fill the void that it leaves behind as it rises.

This doesn’t just bring more warm water toward the glacier — it does so in a turbulent way. “As it’s going up the front of the glacier, it kind of goes up in a corkscrew fashion,” Schild says. “It kind of creates a tornado as it goes up the front of this glacier, it’s bringing in that warm ocean water that then is hitting the terminus of the glacier.” This creates much more melting than would occur if the warm ocean water simply pressed steadily against the glacier front.

And that’s just one effect. The study also found that these meltwater plumes destabilize glacier fronts in another way. Over the winter in Greenland, the waters in front of glaciers develop a thick covering made up of sea ice and chunks of icebergs. This ice “melange,” as the researchers put it, freezes against the front of the glacier and acts to stabilize it.

But the meltwater plumes, the study showed, rise up early in the Greenland melt season and take chunks out of the ice melange. And no wonder — they mix with warm water as they rise to the surface, and so both their velocity and also their temperature help break up the ice and set the stage for the glacier to start calving new icebergs.

And as if that’s not enough, the plume observations also led to yet another conclusion: There appear to be significant pockets of liquid water stored beneath Rink Glacier — water that does not freeze because of the incredible pressure that it’s under. And these pockets should also speed the glacier’s flow toward the sea — glaciers move much more rapidly atop water than they do when grinding against bedrock.

The scientists were able to infer the existence of these subglacial storage chambers based on the timing of the plumes, which continued to form more than 20 days after Greenland’s surface melting itself had ceased as summer came to a close. “As soon as it stops melting on the surface, we still see plumes up to almost a month later, coming out of the glacier,” Schild said. “And so that water is getting stuck, and it’s getting trapped underneath the glacier.”

The presumption, of course, is that while every glacier is different, similar processes could be playing out at many other glaciers besides Rink — including monsters like Jakobshavn.

If you put all these pieces together, then, you can begin to see why global warming can be so devastating to Greenland. It warms the ocean, allowing warmer seas to come visit marine glaciers — but it also warms the atmosphere, leading to melting high atop Greenland’s surface.

Each of these elements, on its own, is bad enough. But their combination is even more dastardly. In fjords at the base of glaciers, the cold water actually acts in concert with the warm to speed up total glacial loss. They’re kind of a dynamic duo.

And in the future, as climate change proceeds, there will be more of both of them.

https://www.washingtonpost.com/news/energy-environment/wp/2016/04/30/another-typical-day-for-greenland-scientists-find-more-reasons-it-will-melt-faster/

Chris Mooney: Scientists are floored by what’s happening in the Arctic right now

Temperature anomalies for January 2016. NASA Goddard Institute for Space Studies 

by Chris Mooney, The Washington Post, February 18, 2016

New data from NASA and the National Oceanic and Atmospheric Administration suggest that January of 2016 was, for the globe, a truly extraordinary month. Coming off the hottest year ever recorded (2015), January saw the greatest departure from average of any month on record, according to data provided by NASA.

[January was the ninth straight month of record breaking global warmth]

But as you can see in the NASA figure above, the record breaking heat wasn’t uniformly distributed — it was particularly pronounced at the top of the world, showing temperature anomalies above 4 degrees Celsius (7.2 degrees Fahrenheit) higher than the 1951 to 1980 average in this region.

Indeed, NASA provides a “zonal mean” version of the temperature map above, which shows how the temperature departures from average change based on one’s latitude location on the Earth. As you can see, things get especially warm, relative to what the Earth is used to, as you enter the very high latitudes:

(NASA Goddard Institute for Space Studies)

Global warming has long been known to be particularly intense in the Arctic — a phenomenon known as “Arctic amplification” — but even so, lately the phenomenon has been extremely pronounced.

[This is where the Earth is most vulnerable to big swings in climate]

This unusual Arctic heat has been accompanied by a new record low level for Arctic sea ice extent during the normally ice-packed month of January, according to the National Snow and Ice Data Center — over 400,000 square miles below average for the month. And of course, that is closely tied to warm Arctic air temperatures.

“We’ve looked at the average January temperatures, and we look at what we call the 925 millibar level, about 3,000 feet up in the atmosphere,” says Mark Serreze, the center’s director. “And it was, I would say, absurdly warm across the entire Arctic Ocean.” The center reports temperature anomalies at this altitude of “more than 6 degrees Celsius (13 degrees Fahrenheit) above average” for the month.

The low sea ice situation has now continued into February. Current ice extent is well below levels at the same point in 2012, which went on to set the current record for the lowest sea ice minimum extent:

(National Snow and Ice Data Center)

“We’re way down, we’re at a record low for this time of year right now,” says Serreze. When it comes to the rest of 2016 and the coming summer and fall season when ice melts across the Arctic and reaches its lowest extent, he says, “we are starting out in a deep hole.”

So what’s causing it all? It’s a complicated picture, say scientists, but it’s likely much of it has to do with the very strong El Niño event that has carried over from 2015. But that’s not necessarily the only factor.

Here's what it means to have the hottest year on record - again

Play Video2:15

Researchers say 2015 was the hottest year on record, and that it "smashed" the previous record, which was 2014. The Post's Chris Mooney explains what that could mean for weather patterns, the Paris climate deal, and 2016. (Gillian Brockell, Chris Mooney/TWP)

“We’ve got this huge El Niño out there, we have the warm blob in the northeast Pacific, the cool blob in the Atlantic, and this ridiculously warm Arctic,” says Jennifer Francis, a climate researcher at Rutgers University who focuses on the Arctic and has argued that Arctic changes are changing mid-latitude weather by causing wobbles in the jet stream. “All these things happening at the same time that have never happened before.”

Serreze agrees that the El Niño has something to do with what’s happening in the Arctic. “I think this is more than coincidence. That we have this very strong El Niño at the same time when we have this absurd Arctic warmth. But exactly what the details are on that, I don’t think we can say right now,” he says.

[Why the U.S. is cutting carbon emissions no matter what happens with the Supreme Court]

In Alaska, matters have been quite warm but not record-breaking this winter, says Rick Thoman, climate science and services manager for the National Weather Service in the state.

“It’s been another warm winter in Alaska,” Thoman says. “No other way to put it. This is the third in a row that’s been significantly warmer than normal.” Alaska’s winter so far (taking into account the months of November, December and January) has been the third warmest on record since 1925, he says.

Still, it all fits a by-now familiar picture of an Arctic warming up considerably faster than the mid-latitudes, with consequences that could extend far outside of the polar region, says Rafe Pomerance, a former deputy assistant secretary of state who sits on the National Academy of Sciences’ Polar Research Board.

Impacts of Arctic warming are usually considered in isolation, and that’s a mistake, he says. “It’s unraveling, every piece of it is unraveling, they’re all in lockstep together,” Pomerance says. “What tends to happen is, everybody nationally reports on the latest piece of news, which is about one system. You hear about the sea ice absent the temperature trend. So you really have to think of it as a whole.”

Indeed, impacts of Arctic warming include the melting of major Arctic glaciers and Greenland (containing the potential for up to 7 meters of sea level rise if it were to melt entirely), the thawing of carbon rich permafrost (which could add to the burden of atmospheric greenhouse gas emissions) and signs of worsening wildfires across the boreal forests of Alaska, to name a few.

If the Arctic is this warm in January and February, then when real warmth comes later this year, these will all be areas to watch.

“I think this winter is going to get studied like crazy, for quite a while,” says Francis. “It’s a very interesting time.”

Study: Global warming is threatening birds

View Photos

A National Audubon Society report predicts that 126 species will experience severe declines.

More at Energy & Environment:

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For more, you can sign up for our weekly newsletter here, and follow us on Twitter here.

Chris Mooney reports on science and the environment.

https://www.washingtonpost.com/news/energy-environment/wp/2016/02/18/scientists-are-floored-by-whats-happening-in-the-arctic-right-now/

WaPo: The melting of Antarctica was already really bad. It just got worse

by Chris Mooney, The Washington Post, March 16, 2015

A satellite view of Antarctica is seen in this undated NASA handout photo obtained by Reuters on February 6, 2012. (NASA handout via Reuters)

This story has been updated.

A hundred years from now, humans may remember 2014 as the year that we first learned that we may have irreversibly destabilized the great ice sheet of West Antarctica, and thus set in motion more than 10 feet of sea level rise.

Meanwhile, 2015 could be the year of the double whammy — when we learned the same about one gigantic glacier of East Antarctica, which could set in motion roughly the same amount all over again. Northern Hemisphere residents and Americans in particular should take note — when the bottom of the world loses vast amounts of ice, those of us living closer to its top get more sea level rise than the rest of the planet, thanks to the law of gravity.

The findings about East Antarctica emerge from a new paper just out in Nature Geoscience by an international team of scientists representing the United States, Britain, France and Australia. They flew a number of research flights over the Totten Glacier of East Antarctica — the fastest-thinning sector of the world’s largest ice sheet — and took a variety of measurements to try to figure out the reasons behind its retreat. And the news wasn’t good: It appears that Totten, too, is losing ice because warm ocean water is getting underneath it.

“The idea of warm ocean water eroding the ice in West Antarctica, what we’re finding is that may well be applicable in East Antarctica as well,” says Martin Siegert, a co-author of the study and who is based at the Grantham Institute at Imperial College London.

[Research casts alarming light on the decline of West Antarctic glaciers]

The floating ice shelf of the Totten Glacier covers an area of 90 miles by 22 miles. It it is losing an amount of ice “equivalent to 100 times the volume of Sydney Harbour every year,” notes the Australian Antarctic Division.

That’s alarming, because the glacier holds back a much more vast catchment of ice that, were its vulnerable parts to flow into the ocean, could produce a sea level rise of more than 11 feet — which is comparable to the impact from a loss of the West Antarctica ice sheet. And that’s “a conservative lower limit,” says lead study author Jamin Greenbaum, a PhD candidate at the University of Texas at Austin.

In its alignment with the land and the sea, the Totten Glacier is similar to the West Antarctic glaciers, which also feature ice shelves that slope out from the vast sheet of ice on land and extend into the water. These ice shelves are a key source of instability, because if ocean waters beneath them warm, they can lose ice rapidly, allowing the ice sheet behind them to flow more quickly into the sea.

The researchers used three separate types of measurements taken during their flights — gravitational measurements, radar and laser altimetry — to get a glimpse of what might be happening beneath the massive glacier, whose ice shelves are more than 1,600 feet thick in places. Using radar, they could measure the ice’s thickness. Meanwhile, by measuring the pull of the Earth’s gravity on the airplane in different places, the scientists were able to determine just how far below that ice the seafloor was.

The result was the discovery of two undersea troughs or valleys beneath the ice shelf — regions where the seafloor slopes downward, allowing a greater depth of water beneath the floating ice. These cavities or subsea valleys, the researchers suggest, may explain the glacier’s retreat — they could allow warmer deep waters to get underneath the ice shelf, accelerating its melting.

Aerial photo of Totten Glacier’s ice shelf edge taken during one of the team’s geophysical survey flights. (Jamin Greenbaum)

In this particular area of Antarctica, Greenbaum says, a warmer layer of ocean water offshore is actually deeper than the colder layers above it, because of the saltwater content of the warm water (which increases its density). And the canyons may allow that warm water access to the glacier base. “What we found here is that there are seafloor valleys deeper than the depth of the maximum temperature measured near the glacier,” Greenbaum says.

One of these canyons is three miles wide, in a region that was previously believed to simply hold ice lying atop solid earth. On the contrary, the new study suggests the ice is instead afloat.

The availability of warm water, and the observed melting, notes the study, “support the idea that the behaviour of Totten Glacier is an East Antarctic analogue to ocean-driven retreat underway in the West Antarctic Ice Sheet (WAIS). The global sea level potential of 3.5 m flowing through Totten Glacier alone is of similar magnitude to the entire probable contribution of the WAIS.”

For Richard Alley, a glaciologist at Penn State University, the new research hints at a possible solution to a question that scientists have long had about the planet’s past — and in particular the Pliocene epoch, beginning 5.3 million years ago, when sea levels were dramatically higher, by as much as 40 meters.

“The sea-level indicators from the Pliocene have suggested that an important amount of ice came out of East Antarctica into the ocean,” says Alley. “Sedimentary records offshore pointed in the same way, and recent modeling…shows the strong potential for this to have happened.  This new paper adds to the evidence — the pieces are fitting together.”

One limitation of the study is that the scientists were not able to directly measure the temperature of ocean water that is reaching the glacier itself. While this could be done with robotic underwater vehicles or other methods, that wasn’t part of the study at this time. Thus, the conclusions are more focused on inferring the vulnerability of the glacier based on a number of different pieces of evidence — topped off by the fact that the glacier is, indeed, retreating.

“What we need now is a confirmation of the findings of the paper from oceanographic data, because it  is one thing to find potential pathways for warm water to intrude the cavity, it is another to show that this is actually happening,” observes Eric Rignot, an Antarctica expert at the University of California, Irvine. “This paper comes short of the latter, but other research efforts are underway to get critical oceanographic information near Totten.”

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Maximum Antarctic sea ice 2014(0:42)

An animation of the Antarctic sea ice between March 21 and September 19, 2014, when the sea ice reached its maximum extent. The red extent line shows the average of the annual maximum extents from 1979 through 2014. (NASA)

For residents of the United States — and indeed, the entire Northern Hemisphere — the impact of major ice loss from Antarctica could be dire. If Antarctica loses volumes of ice that would translate into major contributions to sea level rise, that rise would not be distributed evenly around the globe. The reason is the force of gravity. Antarctica is so massive that it pulls the ocean toward it, but if it loses ice, that gravitational pull will relax, and the ocean will slosh back toward the Northern Hemisphere — which will experience additional sea level rise.

For the United States, the amount of sea level rise could be 25 percent or more than the global average.

[The U.S. has caused more global warming than any other country. Here's how the Earth will get its revenge.]

Much as with the ocean-abutting glaciers of West Antarctica, just because a retreat has been observed — and because the entirety of the region implies a sea level rise of 11 or more feet were all ice to end up in the ocean — does not mean that we’ll see anything near that much sea level rise in our lifetimes. These processes generally are expected to play out over hundreds of years or more. They would reshape the face of the Earth – but we may never see it.

The problem, then, is more the world we’re leaving to our children and grandchildren — because once such a gigantic geophysical process begins, it’s hard to see how it comes to a halt. “With warming oceans, it’s difficult to see how a process that starts now would be reversed, or reversible, in a warming world,” Siegert says.

Update: This article was updated to correct the size of the Totten Glacier. According to Greenbaum (but contrary to this press release), its floating portion (or ice shelf) is 90 miles by 22 miles in size. 

http://www.washingtonpost.com/news/energy-environment/wp/2015/03/16/the-melting-of-antarctica-was-already-really-bad-it-just-got-worse/