Crack in the Antarctic!

From the University of Texas at Austin, a press release to tell us the ice shelves in the Antarctic peninsula are losing their grip and cracking a bit. That could be tragic, except, well, sea ice in Antarctica is growing.

And, there’s only a 40 year historical context for these observations. I just can’t too excited about this.  – Anthony

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West Antarctic Ice Shelves Tearing Apart at the Seams

Posted on March 26, 2012

Rifts in Pine Island Glacier 2011

Rifts along the northern shear margin of Pine Island Glacier (upper right of image). Credit: Michael Studinger, NASA’s Operation IceBridge.

A new study examining nearly 40 years of satellite imagery has revealed that the floating ice shelves of a critical portion of West Antarctica are steadily losing their grip on adjacent bay walls, potentially amplifying an already accelerating loss of ice to the sea.

The most extensive record yet of the evolution of the floating ice shelves in the eastern Amundsen Sea Embayment in West Antarctica shows that their margins, where they grip onto rocky bay walls or slower ice masses, are fracturing and retreating inland. As that grip continues to loosen, these already-thinning ice shelves will be even less able to hold back grounded ice upstream, according to glaciologists at The University of Texas at Austin’s Institute for Geophysics (UTIG).

Reporting in the Journal of Glaciology, the UTIG team found that the extent of ice shelves in the Amundsen Sea Embayment changed substantially between the beginning of the Landsat satellite record in 1972 and late 2011. These changes were especially rapid during the past decade. The affected ice shelves include the floating extensions of the rapidly thinning Thwaites and Pine Island Glaciers.

“Typically, the leading edge of an ice shelf moves forward steadily over time, retreating episodically when an iceberg calves off, but that is not what happened along the shear margins,” says Joseph MacGregor, research scientist associate and lead author of the study. An iceberg is said to calve when it breaks off and floats out to sea.

“Anyone can examine this region in Google Earth and see a snapshot of the same satellite data we used, but only through examination of the whole satellite record is it possible to distinguish long-term change from cyclical calving,” says MacGregor.

The shear margins that bound these ice shelves laterally are now heavily rifted, resembling a cracked mirror in satellite imagery until the detached icebergs finally drift out to the open sea. The calving front then retreats along these disintegrating margins. The pattern of marginal rifting and retreat is hypothesized to be a symptom, rather than a trigger, of the recent glacier acceleration in this region, but this pattern could generate additional acceleration.

“As a glacier goes afloat, becoming an ice shelf, its flow is resisted partly by the margins, which are the bay walls or the seams where two glaciers merge,” explains Ginny Catania, assistant professor at UTIG and co-author of the study. “An accelerating glacier can tear away from its margins, creating rifts that negate the margins’ resistance to ice flow and causing additional acceleration.”

Amundsen Sea Embayment Map

Location of Amundsen Sea Embayment

The UTIG team found that the largest relative glacier accelerations occurred within and upstream of the increasingly rifted margins.

The observed style of slow-but-steady disintegration along ice-shelf margins has been neglected in most computer models of this critical region of West Antarctica, partly because it involves fracture, but also because no comprehensive record of this pattern existed. The authors conclude that several rifts present in the ice shelves suggest that they are poised to shrink further.

This research is sponsored in part by the National Science Foundation.

The article, titled “Widespread rifting and retreat of ice-shelf margins in the eastern Amundsen Sea Embayment between 1972 and 2011”, appears in issue #209 of Journal of Glaciology.

West Antarctic Ice Shelves – Then and Now

(click to download high resolution version):

West Antarctic Ice Shelves Then and Now

Pairs of Landsat satellite images showing changes in ice shelf margins in the eastern Amundsen Sea Embayment in West Antarctica between 1972 and 2011. The striping visible in the 2011 images is due to an unrepaired malfunction in the Landsat-7 platform that occurred in 2003.

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UPDATE: Gail Combs adds this background info in comments:

Velocities of Pine Island and Thwaites Glaciers, West Antarctica, From ERS-1 SAR images

ABSTRACT:

Average velocities of Pine Island and Thwaites Glaciers were measured for the time periods between 1992 and 1994 by tracking ice-surface patterns. Velocities of the central flow of the Pine Island Glacier range from 1.5 km/yr above the grounding line (separating the grounded from the floating parts of a glacier) to 2.8 km/yr near the terminus; velocities of the central Thwaites Glacier range from 2.2 km/yr above the grounding line to 3.4 km/yr at the limit of measurements on the tongue. Both glaciers show an increase in velocity of about 1 km/yr where they cross their grounding lines. The velocities derived from ERS-1 images are higher than those previously derived from Landsat images, perhaps reflecting acceleration of the glaciers. Both glaciers are exceptionally fast. The high velocities may be due to high precipitation rates over West Antarctica and the lack of a major buttressing ice shelf.

Keywords: ERS-SAR images, Pine Island Glacier, Thwaites Glacier, glacier velocity, glacier tongue, glacier terminus

http://earth.esa.int/workshops/ers97/papers/lucchitta/

Antarctic volcanoes identified as a possible culprit in glacier melting

…”This is the first time we have seen a volcano beneath the ice sheet punch a hole through the ice sheet” in Antarctica, Vaughan said.

Volcanic heat could still be melting ice to water and contributing to thinning and speeding up of the Pine Island glacier, which passes nearby, but Vaughan said he doubted that it could be affecting other glaciers in western Antarctica, which have also thinned in recent years. Most glaciologists, including Vaughan, say that warmer ocean water is the primary cause of thinning.

Volcanically, Antarctica is a fairly quiet place. But sometime around 325 B.C., the researchers said, a hidden and still active volcano erupted, puncturing several hundred yards of ice above it. Ash and shards from the volcano carried through the air and settled onto the surrounding landscape. That layer is now out of sight, hidden beneath the snows that fell during the next 2,300 years…..

http://www.nytimes.com/2008/01/20/world/europe/20iht-climate.4.9358350.html

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StuartMcL

Between 1972 and now!
How did it change between 1972 and 1979 when all the other polar ice coverage data starts?
Amazing how they can suddenly find earlier data when it suits the narrative.

Markus Fitzhenry

So excited you left out ‘get’.
I’m excited too. Hopefully, many other commentators will also get excited as they should with most of your finely excited posts. But I digress.
In Scotland they have recently ceased the plantation of grasses on sand dunes as a means to stop erosion. A sand dune ecosystem relies on wind changing the structure of the dunes. Similarly, what’s the problem with Antarctic ice sheets dynamically moving into a position relative to the natural systems around them. Changing glacier flows are a natural occurrence. Where does the now paradigm of glacial theory say ice sheets move in a never ending extension to the Oceans?

Carol

We’re all going to die…aaaargggaahhh!

Village Idiot

“…ice shelves in the Antarctic peninsula are losing their grip and cracking a bit. That could be tragic, except, well, sea ice in Antarctica is growing”
Since when could ice shelf extent be compared to Antarctic sea ice extent? Apples and pears, surely?

[snip . . please repost without the shouting. WUWT folk don’t like to be shouted at . . thanks . . kbmod]

cRR Kampen

“… the ice shelves in the Antarctic peninsula are losing their grip and cracking a bit. That could be tragic, except, well, sea ice in Antarctica is growing.”
No connection, of course. Because the shelf ice never goes to sea, but to Niburu.

Heystoopidone

Southern Hemisphere sea ice can extend to roughly 50 degrees south. Moreover, Antarctic sea ice does not extend southward to the pole; it can only fringe the continent.
Because of this geography, the Antarctic’s sea ice coverage is larger than the Arctic’s in winter, but smaller in the summer. Total Antarctic sea ice peaks in September—the end of Southern Hemisphere winter—historically rising to an extent of roughly 18 million square kilometers (about 6.9 million square miles). Ice extent reaches its minimum in February, when it dips to roughly 3 million square kilometers (about 1.2 million square miles).

Mike Jowsey

This looks like an interesting glaciological study and should improve our understanding of the mechanics of accelerated glaciation. It also focuses on possible positive feedbacks and improving computer modeling of glaciation. Why not? Good science, I say. No mention of CAGW – simply observation of accelerated glaciation in this (small) area of West Antarctica. But I guess the alarmists will tout it as proof of some imminent tipping point, rather than consider the short time frame and small area of the study. The rest of this enormous continent is doing all sorts of growing, calving, shrinking, snowing, expanding, freezing, melting – has been for a gazillion years.

furyforever

http://nsidc.org/cryosphere/seaice/characteristics/difference.html
The description given in the last table on the page above indicates that the variation in minimum and maximum extent is quite large for Antarctica. And also that the ice loss is greater in the Arctic by percent than the gain in the Antarctic. However given this discussion is about sea ice as opposed to talking about land ice wouldn’t it be expected that that sea ice increases as ice calving increases and this is a consistent mechanism with the rifts found in the Thwaites glacier? In other words, isn’t it a real indication of this process actually requiring comparison with land ice? It seems to have no context to me otherwise.

Kelvin Vaughan

Carol says:
March 28, 2012 at 12:33 am
We’re all going to die…aaaargggaahhh!
It’s ok we don’t really exist we just think we do!

tokyoboy

The same phenomenon must have taken place countlessly from time immemorial.

Golly, ice shelves break up. I’m shocked…
(Last thing I’d want to see is ice shelves extending and never breaking, if that ever happens, we’re headed for Iceball Earth again…)
Two added notes:
1) Isn’t this on / near the warming peninsula? That part of Antarctica to have a bunch of volcanoes and warming dirt under the ice? As the rest of Antarctica is getting colder, to have ice growing where it’s colder and breaking off a bit where the land is warming seems quite reasonable.
2) With the solar sleepy time the UV dropped. That let the air column shorten. I’ve observed a return of the stronger more blustery winds of the 1950s and ’60s (and potentially a bit more so). Now assuming this holds near Antarctica too (do we have wind data there?) that would lead to larger waves and a faster circumpolar current. I’d fully expect that to put more ‘tearing’ force on an ice shelf; and more up / down flexing fracturing the margins too. Do we have circumpolar current speed data anywhere? ( IMHO, the spike of cold water we saw in the last few years out into the central Pacific from S. America is evidence for a faster circumpolar current whacking into Drake Passage and sending the ‘excess’ up the coast of S. America. To the extent that is true, the Antarctic side of Drake Passage ought to be getting more currents and pressure too.)
So I think it’s an interesting observation on the ice sheet and land mooring at the margins, but think it’s more likely related to #1 and #2 above and unrelated to air temperatures.

AndyG55

I’m gunna get famous by inventing a new word for this hitherto unknown phenomenumenum.
I’m gunna call it “calving”..

Mardler

For “ice shelves in the Antarctic peninsula are losing their grip and cracking a bit” read “warmist scaremongers everywhere are losing their grip and cracking a bit”

Otter

I seem to recall somewhere, a few years back, seeing a little bit of math about the size of this bay they are speaking about. I wish I could recall where….. However, it something along the lines of this region being 2% of the Antarctic peninsula, which was 2% of the entire continent. Can anyone verify that?
And if that is anywhere near close, can anyone tell me why focusing on .4% of the continent, equates to the entire continent, in the minds of AGW True Believers?

Jimbo

It’s great to see that they are prepared to go back to 1972 for Antarctica. Will the IPCC do it again for the Arctic or will they continue to delete records in any forthcoming report? In the meantime what’s the panic when over the period Antarctic sea ice has grown?
Proof of accelerating rising sea levels. Head for the hills!!!!! 😉

Sea level has been plummeting for four years, and is lower than it was in 2003 when EU’s Envisat satellite was launched.
http://www.real-science.com/proof-ice-sheets-melting

Even the Guardian is alarmed.

While global temperatures have increased, overall Antarctic air temperatures have fallen slightly, although they have increased over the Antarctic Peninsula and West Antarctica. At the same time, the overall extent of Antarctic sea ice has slightly increased
http://www.guardian.co.uk/environment/2012/mar/02/is-antarctica-getting-warmer?intcmp=122

http://www.sciencedaily.com/releases/2007/12/071210094332.htm

Keith Minto

Reporting in the Journal of Glaciology, the UTIG team found that the extent of ice shelves in the Amundsen Sea Embayment changed substantially between the beginning of the Landsat satellite record in 1972 and late 2011. These changes were especially rapid during the past decade.

But looking at this graph of Pine Island glacier velocity, at least from 2005, there seems to be a plateau in velocity. This would depend upon thermal activity under the glacier and more detail about this by the authors would be welcome.
Here is an overview of Pine Island glacier.

H.R.

Whoa, Anthony!
Careful what you’re doing to people who read your posts early in the morning before they’ve had enough coffee to get going.
First thing that I see on WUWT at 5:00 am is “Crack In The Antacrtic” and I think “Wow! Drugs are everywhere nowadays.”
Of course reading further… well, as Emily Litella would say, “Nevermind.”

izen

@-And, there’s only a 40 year historical context for these observations. I just can’t too excited about this. – Anthony
While the direct observation may only cover 40 years, the ice SHELVES (not sea ice) that are being observed CAN be dated and so the context is of large ice shelves which have been stable features at least throught the Holocene starting to collapse, long after the post-glacial Holocene maximum. In most previous interstadial cycles these ice masses would be expanding, not shrinking several thousand years after the maximum post-melt temperature.

Hot under the collar

Ice shelves losing their grip, eh.
Where’s Garfield when you need him?

This is really bad.

ntesdorf

“West Antarctic Ice Shelves Tearing Apart at the Seams”.
I read this quickly as, “West Antarctic Ice Shelves Tearing Apart at the Scams”.
Somehow this seems to be more likely than the originally intended heading.

H.R.

“Crack In The Antarctic!”
Dang! Drugs are everywhere now…. oh wait…. nevermind.

Cold Englishman

Ice breaks up floats in sea……… Titanic meet Iceberg!
Really, who pays for all this twaddle? Oh don’t ask, its you and me.

How was it changing before LANDSAT?

“Typically, the leading edge of an ice shelf….. ”
Ay, there’s the rub! As if it is known from our limited observation in time and space, what is “typical” in Antarctica and what is anomalous.

Jason H

A few years ago, there was talk about volcanic activity up and down that region of west Antarctica.

Sea ice has little to do with shelf ice, so the comparison is meaningless.

kadaka (KD Knoebel)

I remember very long-period ocean waves (“infragravity waves”) being implicated in the collapse of Antarctic ice shelves like with the Wilkins Ice Shelf breakup events in 2008. Worrying about CO₂ ain’t gonna save these shelves.
But it may indicate the Southern Ocean might be a good place to test those future ocean-based renewable-energy wave generators, as besides dragging out “climate change” as a project justification, they can claim the need to intercept all that energy before the ice shelves collapse yielding a 3 meter (+0.01/-3.01) sea level rise. Hansen would be pleased.

…ice shelves in the Antarctic peninsula are losing their grip and cracking a bit.
Proof that Antarctic ice shelves are therefore a suitable proxy for CAGW cultists…

agwnonsense

They mentioned acceleration of the ice flow which would indicate increased snowfall.If the average temp in Antarctica is -40 c then logic dictates it’s not melting ,I would suggest that our Beautiful Planet with it’s EVER CHANGING CLIMATE is F——-G with their tiny brains.Climate Change is Natural get over it.

izen says:
March 28, 2012 at 2:29 am
…so the context is of large ice shelves which have been stable features at least throught the Holocene starting to collapse, long after the post-glacial Holocene maximum.

No, they’re not starting to collapse. They’ve become detached, most likely due to volcanic warming. It’s now autumn in the Southern Hemisphere — in a few months the rifts should be frozen over again.
In most previous interstadial cycles these ice masses would be expanding, not shrinking several thousand years after the maximum post-melt temperature.
Ahem — what is it about “recent volcanic ground warming” that you didn’t understand?

Bloke down the pub

As I see it, the ice that slides off the continent into the sea has two options. It can either break off and float away and melt, or it can keep on expanding Northwards. Do they have any evidence that it has done the later in the last 10,000 years, if so I think we should be told.

AnonyMoose

“no comprehensive record of this pattern existed.”
So they don’t know if what they describe is common nor unusual.

LazyTeenager

sea ice in Antarctica is growing.
———–
So the article is about land ice and Anthony mentions sea ice. Is anyone here confused by the distinction?
Maybe land ice moving faster means the Antarctic is getting warmer. Maybe more land ice melting is making it easier for seawater to freeze and make more sea ice?

Geoff Sherrington

“Losing its grip”
Johnny Weissmuller played Tarzan in several movies, swinging from the vines with bravado. Later, he had the misfortune of dementia and was put into a care home. One evening he made a leap from a balcony to swing on a chandelier, but failed. Unkind newspaper headlines next day were “Tarzan Loses His Grip”.
It’s not my fault.

Geoff Sherrington

Sorry, I thought this was a page about cracks about the Antarctic.

Steve Keohane

Kelvin Vaughan says: March 28, 2012 at 1:19 am
Carol says: March 28, 2012 at 12:33 am
We’re all going to die…aaaargggaahhh!
It’s ok we don’t really exist we just think we do!

In that vein, ‘What you don’t think can’t hurt you’. Firesign Theatre

Lazy Teen says:
“So the article is about land ice and Anthony mentions sea ice. Is anyone here confused by the distinction?”
You mean: is anyone else confused…

Gail Combs

These should be added to that article to give background information..

Velocities of Pine Island and Thwaites Glaciers, West Antarctica, From ERS-1 SAR images
ABSTRACT:
Average velocities of Pine Island and Thwaites Glaciers were measured for the time periods between 1992 and 1994 by tracking ice-surface patterns. Velocities of the central flow of the Pine Island Glacier range from 1.5 km/yr above the grounding line (separating the grounded from the floating parts of a glacier) to 2.8 km/yr near the terminus; velocities of the central Thwaites Glacier range from 2.2 km/yr above the grounding line to 3.4 km/yr at the limit of measurements on the tongue. Both glaciers show an increase in velocity of about 1 km/yr where they cross their grounding lines. The velocities derived from ERS-1 images are higher than those previously derived from Landsat images, perhaps reflecting acceleration of the glaciers. Both glaciers are exceptionally fast. The high velocities may be due to high precipitation rates over West Antarctica and the lack of a major buttressing ice shelf.
Keywords: ERS-SAR images, Pine Island Glacier, Thwaites Glacier, glacier velocity, glacier tongue, glacier terminus
http://earth.esa.int/workshops/ers97/papers/lucchitta/

Antarctic volcanoes identified as a possible culprit in glacier melting
…”This is the first time we have seen a volcano beneath the ice sheet punch a hole through the ice sheet” in Antarctica, Vaughan said.
Volcanic heat could still be melting ice to water and contributing to thinning and speeding up of the Pine Island glacier, which passes nearby, but Vaughan said he doubted that it could be affecting other glaciers in western Antarctica, which have also thinned in recent years. Most glaciologists, including Vaughan, say that warmer ocean water is the primary cause of thinning.
Volcanically, Antarctica is a fairly quiet place. But sometime around 325 B.C., the researchers said, a hidden and still active volcano erupted, puncturing several hundred yards of ice above it. Ash and shards from the volcano carried through the air and settled onto the surrounding landscape. That layer is now out of sight, hidden beneath the snows that fell during the next 2,300 years…..
http://www.nytimes.com/2008/01/20/world/europe/20iht-climate.4.9358350.html

With all that potential water vapor locked up in ice, on the north and south poles does anyone else think that this could mean a dry spell for some areas this year?

Gail Combs

H.R. says:
March 28, 2012 at 2:24 am
Whoa, Anthony!
Careful what you’re doing to people who read your posts early in the morning before they’ve had enough coffee to get going.
First thing that I see on WUWT at 5:00 am is “Crack In The Antacrtic” and I think “Wow! Drugs are everywhere nowadays.”
Of course reading further… well, as Emily Litella would say, “Nevermind.”
___________________________________________________
Yeah, I know what you mean. I read “Crack In The Antarctic” and thought OH MY a large earthquake was cracking the Antarctic glacier. Something akin to what is being seen in Africa.
Death of a Continent, Birth of an Ocean
Africa’s Afar region gives glimpses of geology in action

….here, on the edge of Africa, the continent is splitting apart. Pulled inexorably by the grind of tectonic plates, Afar is ripping asunder like a gateway to hell. Molten rock wells up from below, pouring onto the sweltering surface.
Yet for all the fire and brimstone, Afar is on its way to a watery end. A million years or so from now, the geological processes that rip the continent will give birth to a new seafloor. And Afar will lie at the bottom of Earth’s freshest ocean.
Until then, researchers have a front seat to an unparalleled physical spectacle. “It’s a really unique opportunity to understand how continents break apart,” says Tim Wright, a remote-sensing expert at the University of Leeds in England. Wright leads a large international consortium that began studying the region in 2005, when the splitting picked up pace…..
http://www.sciencenews.org/view/feature/id/331389/title/Death_of_a_Continent,_Birth_of_an_Ocean_

Exciting stuff! Well at least if you like Geology. I though this was something similar instead it is just the usual Greenie twisting of facts.

Dave Bradley

Now, as I understand it, an ice shelf is ice that is anchored to land and extends out over the water. It would seem to me that if the ice thickness were to increase, it would reach a point that the end would be too heavy (because it is not supported by land) and there would be a break. So, cracking of an ice shelf could be because it has gained too much weight. I am no scientist, so I would appreciate it if someone would correct me if I am wrong.

abqben

How has the resolution of the imagery changed since 1972, and can that have an impact on the visibility of surface features? The resolution of the sensors has improved dramatically since 1972. The Landsat 2, launched in 1975, had 80 meter resolution from its multispectral camera system. (http://landsat.usgs.gov/about_landsat2.php) Landsat 7 (since 1999) has multiple sensors with 30 meter resolution. (http://landsat.usgs.gov/about_landsat7.php)
Just looking at those pictures above, I am not sure they can really tell us anything, given the difference in visible surface features.
Ben

Chuck Nolan

First, you know the climate changes or it doesn’t.
If you know it does change then it must either get colder or warmer and get more or less precipitation. Therefore, any reasonable thinker would understand the ice will change.

LazyTeenager says:
March 28, 2012 at 4:15 am

Maybe land ice moving faster means the Antarctic is getting warmer. Maybe more land ice melting is making it easier for seawater to freeze and make more sea ice?

Yay! Double-think!
So more ice is proof of Global Warming!
And less ice is proof of Global Warming!
Win win!

Bill Illis

This crackin the Pine Island Glacier was first noticed 12 years ago. It has hardly changed at all since that time.
They just keep flying over it, again and again, and sounding the alarm as if it were new.
First satellite picture of it from 2000.
ftp://sidads.colorado.edu/pub/DATASETS/ICESHELVES/pine/aster_pig_20001212_ov_nobox.jpg
Earth Observatory article talking about it showing pictures from 2001.
http://earthobservatory.nasa.gov/IOTD/view.php?id=76437
In fact, the current 2012 images show the crack is not as wide as it was 12 years ago.

Admad

Otter said “…can anyone tell me why focusing on .4% of the continent…”
Sorry to troll you sir, but 2% of 2% is 0.04% – ya lost a zero there.
Pip pip.

Willem De Rode

Yes, over a period of 30-35 years the trend of the Antartic sea ice is growing. But if we might say that the global temperature is not rising anymore since 2008….then we have to be honnest and say also that the Antartic sea ice is not growing anymore since then ! More “warming-like people” can possibly say that the Antartic sea ice is declining since 2008…and there is no argument in the observations to contradict them !

Most glaciologists, including Vaughan, say that warmer ocean water is the primary cause of thinning.
Silly me. Here I’d always thought that glaciers moved over *land* — and a combination of sublimation and a dearth of snowfall was the primary cause of glaciers thinning.