Upwelling seawater along parts of Pine Island Glacier Ice Shelf has carved out caves in the ice.
The news release by Columbia University’s Earth Institute explains:
Stronger ocean currents beneath West Antarctica’s Pine Island Glacier Ice Shelf are eroding the ice from below, speeding the melting of the glacier as a whole, according to a new study in Nature Geoscience. A growing cavity beneath the ice shelf has allowed more warm water to melt the ice, the researchers say—a process that feeds back into the ongoing rise in global sea levels. The glacier is currently sliding into the sea at a clip of four kilometers (2.5 miles) a year, while its ice shelf is melting at about 80 cubic kilometers a year – 50 percent faster than it was in the early 1990s – the paper estimates.
We knew that Pine Island Glacier (PIG) is disintegrating much faster than almost anybody imagined — see “Nothing in the natural world is lost at an accelerating exponential rate like this glacier” (8/09). And we knew deep ocean heat is rapidly melting Antarctic ice (12/10), which noted: “Global warming is sneaky. For more than a century it has been hiding large amounts of excess heat in the world’s deep seas. Now that heat is coming to the surface again in one of the worst possible places: Antarctica.”
This new study, “Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf” (subs. req’d), gives us a better understanding of just how PIG is being undermined from underneath: “We conclude that the basal melting has exceeded the increase in ice inflow, leading to the formation and enlargement of an inner cavity under the ice shelf within which sea water nearly 4◦C above freezing can now more readily access the grounding zone.
Here is a particularly remarkable observation the scientific team made one day:
One day, near the southern edge of Pine Island Glacier Ice Shelf, the researchers directly observed the strength of the melting process as they watched frigid, seawater appear to boil on the surface like a kettle on the stove. To Jacobs, it suggested that deep water, buoyed by added fresh glacial melt, was rising to the surface in a process called upwelling. Jacobs had never witnessed upwelling first hand, but colleagues had described something similar in the fjords of Greenland, where summer runoff and melting glacier fronts can also drive buoyant plumes to the sea surface.
In 2001, the IPCC “consensus” said neither Greenland nor Antarctica would lose significant mass by 2100. They both already are. As Penn State climatologist Richard Alley said in March 2006, the ice sheets appear to be shrinking “100 years ahead of schedule.” And the ice loss is accelerating (see “JPL bombshell: Polar ice sheet mass loss is speeding up, on pace for 1 foot sea level rise by 2050“).
Accelerated disintegration of the West Antarctic ice sheet (WAIS) is most worrisome (at least for this century) because it’s going to disintegrate long before the East Antarctic Ice Sheet does. Not only is the WAIS melting from underneath, it is, as I wrote in the “high water” part of my book, inherently less stable:
Perhaps the most important, and worrisome, fact about the WAIS is that it is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level. The WAIS rests on bedrock as deep as two kilometers underwater. One 2004 NASA-led study found that most of the glaciers they were studying “flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way.” A 2002 study in Science examined the underwater grounding lines-the points where the ice starts floating. Using satellites, the researchers determined that “bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed.” And that melt rate is positively correlated with ocean temperature.
The warmer it gets, the more unstable WAIS outlet glaciers will become. Since so much of the ice sheet is grounded underwater, rising sea levels may have the effect of lifting the sheets, allowing more-and increasingly warmer-water underneath it, leading to further bottom melting, more ice shelf disintegration, accelerated glacial flow, and further sea level rise, and so on and on, another vicious cycle. The combination of global warming and accelerating sea level rise from Greenland could be the trigger for catastrophic collapse in the WAIS (see, for instance, here).
The time to act was a while ago, but now is far better than later.
- Satellite data stunner: “Our data suggest that EAST Antarctica is losing mass” — Antarctica may soon be contributing significantly more to global sea-level rise.”
- Nature: “Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized.”
- Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100
- Antarctica has warmed significantly over past 50 years
- West Antarctic ice sheet collapse even more catastrophic for U.S. coasts
Below are the earlier comments from the Facebook commenting system:
Look on the bright side: better to see currents taking warm water to PIG and disintegrating ice sheets than doing the same on the Arctic Shelf and triggering methane releases.
These thoughts sound a little weird and fatalistic, but we might as well get used to it. And use it as an excuse to fight that much harder.
My guess is, once the ice is gone, the lowered albedo will trigger a sudden methane surge. Further the gravitation imbalance will create a surge in seismic activity. Basically the entire northern hemisphere will become a very unstable sector. I doubt the humans can keep up infrastructure or fly/sail around, without heavy tolls.
We witness the onset of this chapter now and as we approach it further, huge population die-offs follow, together with chaos and anarchy. Possibly rendering any serious affords impossible.
We have to act now “The critical Decade”, but we probably won’t.
June 27 at 11:30pm
What is more?
That nobody seems to acknowledge that the vanishing ice is the harbinger of catastrophic climate changes. Already it becomes visible that 1 or 2 Degree Celsius or very likely even more temperature rise will kill of huge amounts of the earth ecosystems and organisms.
The foundations which enable our growth – of the human race, is about to collapse.
The government has to act aggressively to halt the denial machine and then build alternative energy, to stop further fueling the climate change with emissions.
As the top of the West Antarctic ice sheet melts it also removes needed weight to hold the ice to the ocean bottom. As soon as it floats it is gone.
Climate change hots up in 2010, the year of extreme weather.
Last year was the joint-warmest on record and also the wettest over land, with sea ice levels dropping and drought on the rise.
I wonder how many nuclear plants will be submerged by 10 to 30 meters of sea level rise?
June 27 at 6:11pm
How about the Houston ship channel.
June 28 at 10:09am
The West Antarctic ice sheet is a potential tipping element of the climate system that might have partially tipped already. According to a study now published in Climatic Change, experts can not rule out that ice masses in the Amundsen Sea sector of Antarctica have already begun to destabilize. This is one of the results of a new assessment of the current state of six potentially unstable regions in the climate system with large direct impacts on Europe.
A partial collapse of the West Antarctic ice sheet for example could be equivalent to an additional 1.5 meters sea level rise, prior research showed. Most dykes in Europe may be elevated by only one meter. Beyond this region-specific threshold significant rebuilding would be necessary. However, the disintegration of this ice sheet might take hundreds of years. Nonetheless the effects could be significant. Apart from releasing water into the oceans, melting of the West Antarctic ice sheet would change the gravitational pull to the pole. Thereby it could lead to an even stronger sea level rise on European coastlines. All of this is incorporated in the scientists’ conclusions.
Harkin: Climate change a factor in flooding.
SIOUX CITY — U.S. Sen. Tom Harkin, D-Iowa, told reporters Monday while overlooking the swollen Missouri River that some revisions need to be made to the Army Corps of Engineers’ master manual but that it’s “not fair” to criticize the corps.
“They just didn’t count on two or three huge rainfalls,” Harkin said while standing with city and county officials at Prospect Hill. “If we didn’t have those rainfalls, their master plan would’ve worked.”.
“I think it’s indisputable that something is happening to our climate,” he said. “Perhaps the basis of that manual needs to be revised for climate change that’s happening and the amount of snowpack.”.
Another feedback into this feed back. My thinking is the Southern Ocean becomes stormier than any of us can imagine. Much more wave energy moving the water column. Jacking all this newly ungrounded ice, up and down.
Ode to Joe Romm:
Why don’t you just ban this little Koch critter?
June 27 at 11:33pm
Joe, block this little troll, New York Nik.
And, where are Ed Hummell, Pete Best, Wyo the organic farmer and Mulga? We need them; their advise and comments. Contact them. Invite them back in.
June 28 at 10:09am
An observed event from Colorado Bob -
ASHLAND , KS 114.0°F 2011-06-27 107.0°F 1998-06-27
PADUCAH , TX 118.0°F 2011-06-27 112.0°F 1994-06-27
June 28 at 11:23am
No way, Prok! Nik’s a funny example of the denialist Rager–a widespread spammer with a totally closed mind who likes to ramp up the holier-than-thou rhetoric. Check the comment stream here for an example: http://www.scholarsandrogues.com/2011/05/18/milloys- op-ed-riddled-errors/ — likes to trot out the argument-from-degree fallacy (Poison Ivy League Fallacy): “my degree is from a more reputable university than yours; therefore, you suck, and everything you say is ridiculous.” Google the handle, but bring appropriate headgear.
Prok, I don’t think it’s a Koch critter; Koch critters don’t usually show the level of bitterness Nik does. I could be wrong, though. It might just be the elaborate iPersona of a Koch Machine apparatchik, or the secret project of an Ayn Rand devotee high schooler.
June 28 at 4:50pm
Sea Level Rise, trigerred by polar ice melt is a major argument to convince people that we must do what is requested by the scientific community, cut our CO2 emissions drastically, even if we would prefer not to change our habits.
For the West Antarctic Ice Sheet (WAIS) my question is why the fact that this ice is grouded underwater is an aggravating feature than not.
I understand that being underwater, the melt by the warming ocean will be stronger.But on the other hand, the whole volume of ice underwater is bigger than the one of the water resulting from the melt, so the impact on the SLR is reduced to the ice over the current level of the sea.
I suppose that the forecast of 6 meters of SLR for the whole WAIS melting takes this principle in account.
Thanks for any clear exponation (as allways on Climate Progress!)
The underwater grounded ice itself does not raise sea level when it melts. But when it disappears it allows ice that is above the surface, but not floating because it’s sitting on grounded ice, to collapse into the sea and allows flow of glaciers on land to accelerate into the sea.
The structures at and under the ice edge control how fast the grounded ice melts.
The sea floor under the WAIS has numerous troughs and ridges, see recently updated bathymetry here http://www.the-cryosphere.net/5/95/2011/tc-5-95-2011.html (pictures in linked full paper).
In places the grounded front edge of ice is resting on a ridge but troughs penetrate closer to shore and let warm seawater reach the coast.
Also, grounded ice could potentially float off the bottom on rising seas, allowing warm water to flow underneath.
June 28 at 12:14pm
Leif: There is not really any melting on the surface of Pine Island Glacier, it is all basal melt that is causing the problem. This was mostly the case for Wilkins Ice Shelf too and <a href=”<a href=”http://glacierchange.wordpress.com/2011/04/28/hariot-glacier/”>Wordie Ice Shelf-Hariot Glacier</a>.
Mauri – Geologists have told me that the summer sun can melt ice cliffs facing the sun in Antarctica – do you know anything about this, and is it significant?
June 30 at 5:27am
Take a look at the location for a cavity to form near the glacier center near the grounding line. http://glacierchange.wordpress.com/2009/11/12/pine-island-glacier-grounding-line/
is this process lovelock’s pipes in action?