Chris Mooney / The Washington Post & James Hamblin / The Atlantic – 2015-03-24 00:46:34
A NASA animation of the Antarctic sea ice between March 21 and Sept. 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.
The Melting of Antarctica Was Already Really Bad. It Just Got Worse
Chris Mooney / The Washington Post
(March 16, 2015) — 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.
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.
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 modelingâ€¦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.”
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.]
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 â€“ 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.
Collapse of the Greenland Ice Fields Caught on Tape
(December 14, 2012) — On May 28, 2008, Adam LeWinter and Director Jeff Orlowski filmed a historic breakup at the Ilulissat Glacier in Western Greenland. The calving event lasted for 75 minutes and the glacier retreated a full mile across a calving face three miles wide. The height of the ice is about 3,000 feet, 300-400 feet above water and the rest below water.
Chasing Ice won the award for Excellence in Cinematography at the 2012 Sundance Film Festival and the Best Documentary from the International Press Association. It has won over 30 awards at festivals worldwide. Still playing in theaters worldwide.
How the Most Important Glacier in East Antarctica Is Melting
James Hamblin / The Atlantic
(March 20 2015) — Even if you’re lucky enough that there’s an ice runway where you want to land in Antarctica, that doesn’t mean the weather will allow you to. And then, even if your plane is equipped to fly for eight hours, at some point, you do have to find a way to stop flying. When that happens to the scientists of the International Collaboration for Exploration of the Cryosphere Through Aerogeophysical Profiling (ICECAP) team, they manage to land “in the middle of nowhere,” according to on-board geophysicist Jamin Greenbaum. Then they camp out. Eventually they’ll be able to make it back to their base.
Greenbaum tells me he’s never been scared. Even though the plane is an Indiana Jones-style Douglas DC-3 that served in World War II. It can deploy skis as landing gear when necessary, and the pilots are a Calgary-based crew, expert at flying in suboptimal conditions.
“We have had some harried situations,” Greenbaum said. For the past eight years he has done annual two-to-five-month deployments to Antarctica to survey the ice. He rides in the cargo hull of the plane, along with 1,000 pounds of ice-penetrating radar, lasers, and magnetic-field mapping equipment. “You know, it’s Antarctica; in 1,500 hours you’re going to have some bad weather. But no, I’ve never once gotten nervous.”
It’s believable; his manner is steady. When we spoke it was broken only by excited descriptions of data collection equipment and the latest findings of the ICECAP team, released Tuesday, which he called “very alarming.”
That alarm is not his alone, nor is it limited to the scientific community. It is because of the ICECAP team that East Antarctica has been a trending topic on Facebook this week — in case you didn’t notice. Or you did, and thought it strange, even by the standards of Facebook trending topics. In recent years most people have been talking about West Antarctica. West Antarctica this and West Antarctica that.
The West Antarctic ice sheet is unstable, and the melting of a major section that contains enough ice to raise sea levels four feet “appears unstoppable,” according to NASA. That alone could be enough to devastate coastal cities worldwide within the not-distant future, not to mention increase storm surges and anomalous severe-weather events worldwide. If that concept hasn’t yet left you subject to “eco-anxiety,” a relatively new concept wherein the sight of an idling tailpipe can render a person catatonic or unwilling to bear children, this week’s news may.
The ICECAP research team, a tight-knit collaboration drawing from the US, U.K., Australia, and France, reported in the journal Nature Geoscience that the largest and fastest-thinning glacier on the east side, Totten Glacier, is subject to the same warm-water currents that are famously eroding the western edge of the continent.
The study explains how warm water is gaining access to the base of the floating part of Totten Glacier, by at least two “gateways” into a large cavity in the ice shelf. Until now there was no evidence that these gateways existed; the sea floor was thought to be too shallow for water to get in. But this explains the existence of the cavity, and the potential for it to continue to grow.
An oddity about the polar regions is that you can get warm water below cold water, which is not intuitive, in that normally heat rises. Because it is extremely salty, this water doesn’t. It can ride along the floor through valleys and melt the glacier from underneath.
And while Totten Glacier is massive, more important than its own mass is the inland ice that it holds back: a “catchment” that is three-quarters the size of Texas. The glacier is like a plug in a bathtub drain, and that plug is melting. Within the catchment area behind it is enough ice to raise sea levels by eleven feet. “And that’s a conservative lower limit,” said Greenbaum, who says the future of East Antarctica is in every way as significant as what’s happening in the West. “It would take [melting] all of the glaciers in West Antarctica that drain its interior basin to raise sea levels by that much.”
Totten Glacier is far from entirely melting, but the discovery suggests that known ice-thinning will accelerate. As excessive carbon dioxide in the atmosphere continues to trap heat, the oceans will continue warming, which will continue melting glaciers, which are so immense that they contain most of the world’s fresh water.
The ice along the coast is thick and deep, about 1.25 miles below sea level in places, explains Greenbaum, who spends his non-Antarctic time at University of Texas at Austin Institute for Geophysics — though he’s constantly Skyping with his colleagues in Tasmania. The enormous depth of the ice is also part of the problem, because when there is enough erosion that the ice starts to float, the volume contributes to the rising sea level, “so the thickness actually works against you.”
Global measures to reduce carbon emissions have been meager and insufficient to prevent fundamental and profound disruption of human existence, and so forth. The season premier of Vice’s HBO show last week depicted the already devastating effects on an underwater village in southern Bangladesh. Similar images of people in the region being forced out of their homes by encroaching seawater have been in the news since at least 2009.
Obvious as this is to people living this reality, and people like Greenbaum who regularly measure glaciers, still only two in three Americans “thinks” that global warming is happening. That rate of acceptance has been steady for a decade. This winter has been “cooler than average” along the East Coast of the United States, according to a report yesterday from the National Climate Center. That feels like understatement at this point. But on a global scale, it was actually yet again the warmest on record.
In the new documentary Merchants of Doubt, filmmaker Robert Kenner (of Food, Inc.) shows how professional climate-change deniers like Marc Morano profit by making that desired belief an easy one simply by cultivating uncertainty. “I’m not a scientist, but I play one on TV,” he says in the film, referring to his appearances on cable news shows as a talking head. There he “debates” scientists, often on Fox News, as a form of pandering to viewers who want to believe that legitimate people will tell them what they want to hear.
He traffics in doubt, he admits in the film. That is all it takes to lead to legislative inaction: Let everyone keep burning fossil fuels until there is more evidence that this is a bad thing. Even though there is abundant evidence; more than there is for most things we do to protect and preserve our health and general continued existence.
Meanwhile Greenbaum and the ICECAP team are also mapping the tectonics under Antarctica. Geothermal heat flux has important implications for how fast the ice can move, factoring into the model of migration toward the coastline. The point is always to understand how the glaciers are going to continue to change, and how that’s going to affect sea levels.
Even if most of the research reports won’t be super popular on Facebook. “This one just got really big because it uncovered this mechanism that makes a lot of sense,” Greenbaum said. “Now we can predict change better than before.”
Greenbaum is vague when it comes to predicting exactly how quickly Totten’s effects on sea levels will play out, as are other climate scientists with regard to the effects in the west. This week’s finding is a step toward a better predictive model. The team will monitor the ocean and use numerical computation models to try and map out the future behavior of the glacier in the context of this newly discovered topography and warm water.
I made a sort of stupid dad joke about him not buying coastal property any time soon, and he didn’t laugh, but explained: “One of our goals is to properly inform coastal communities about what infrastructure is needed.”
James Hamblin, MD, is a senior editor at The Atlantic. He writes the health column for the monthly magazine and hosts the video series If Our Bodies Could Talk.
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