Massive Antarctic ice shelf on verge of breakup

[bascule]

http://www.cnn.com/2008/TECH/science/03/25/antarctic.ice/index.html

 

Despite allegations by the climate change denialist blogosphere that everything's fine and dandy down in the Antarctic, 220 square miles of an Antarctic ice shelf has broken up and collapsed into the ocean, with an additional 5,282 square miles, comparable to the state of Connecticut or about half the area of Scotland, also on the verge of breakup.

[Psycho]

Well according to this News organisation who I would trust far more than CNN it is about the size of the isle of man which is far smaller than half of Scotland, and according to that it was only 40 square miles.

 

Plus the fact it has yet to break off it has just cracked, some expect it to stay in place as the Antarctic summer is ending and to see what happens in the spring.

[bascule]

Oh boy, an ad hominem against CNN.

 

Let's skip the news organizations and go straight to the scientists to settle this dispute, shall we?

 

http://nsidc.org/news/press/20080325_Wilkins.html

 

Satellite imagery from the National Snow and Ice Data Center at the University of Colorado at Boulder reveals that a 13,680 square kilometer (5,282 square mile) ice shelf has begun to collapse because of rapid climate change in a fast-warming region of Antarctica.

 

The Wilkins Ice Shelf is a broad plate of permanent floating ice on the southwest Antarctic Peninsula, about 1,000 miles south of South America. In the past 50 years, the western Antarctic Peninsula has experienced the biggest temperature increase on Earth, rising by 0.5 degree Celsius (0.9 degree Fahrenheit) per decade. NSIDC Lead Scientist Ted Scambos, who first spotted the disintegration in March, said, "We believe the Wilkins has been in place for at least a few hundred years. But warm air and exposure to ocean waves are causing a break-up."

 

Satellite images indicate that the Wilkins began its collapse on February 28; data revealed that a large iceberg, 41 by 2.5 kilometers (25.5 by 1.5 miles), fell away from the ice shelf's southwestern front, triggering a runaway disintegration of 405 square kilometers (160 square miles) of the shelf interior (Figure 1). The edge of the shelf crumbled into the sky-blue pattern of exposed deep glacial ice that has become characteristic of climate-induced ice shelf break-ups such as the Larsen B in 2002. A narrow beam of intact ice, just 6 kilometers wide (3.7 miles) was protecting the remaining shelf from further breakup as of March 23 (Figure 2).

 

So:

 

Initial collapse: 102.5 km^2 (38.25 square miles)

Subsequent "runaway disintegration": 405 km^2 (160 square miles)

Total collapsed portion: 507.5 km^2 (198.25 square miles)

Total ice shelf extent: 13,680 square kilometer (5,282 square mile)

[Psycho]

You posted it as if the whole ice shelf has fallen off into the sea and with your bias against people who denounce climate change, I thought I would tell people what has actually happened.

 

Whereas I agree that climate change is happening and to an large extent it is probably humans fault, that is no reason to spin the facts, as if the facts are there they will speak for themselves.

[bascule]

You posted it as if the whole ice shelf has fallen off into the sea

 

Read harder, Homer:

 

220 square miles of an Antarctic ice shelf has broken up and collapsed into the ocean, with an additional 5,282 square miles, comparable to the state of Connecticut or about half the area of Scotland, also [b']on the verge of breakup.[/b]

 

Satellite imagery from the National Snow and Ice Data Center at the University of Colorado at Boulder reveals that a 13,680 square kilometer (5,282 square mile) ice shelf has begun to collapse[/b'] because of rapid climate change in a fast-warming region of Antarctica.

 

bias [...] spin [...'] if the facts are there they will speak for themselves.

 

Yeah, that's pretty much the denialist attitude in a nutshell...

[CaptainPanic]

It's the volume of 5 times the Wembley Stadium in London, with a surface area of 400 tennis fields. The mass is equivalent to 90000 African elephants, and at the speed it moves it would take 600 million years to go to the moon and back!... right.

 

Note that this is a sarcastic post about the media. And since the media nowadays also read forums and blogs, this forum is in fact also guilty of providing poor information (so therefore I thank Bascule for providing the numbers (with metric units) in the second post).

[JohnB]

Bascule, maybe you should read harder. As the man said;

"

We believe the Wilkins has been in place for at least a few hundred years. But warm air and exposure to ocean waves are causing a break-up."

A few hundred years? OMG, an ice shelf that appears to have formed during the Little Ice Age is collapsing. Gee, could that be because, let me think, we're not in a Little Ice Age anymore?

 

Or maybe, from a NY Times article;

The thinning of the Pine Island and Thwaites glaciers ''may be a direct impact of global warming that happened 20,000 years ago,'' said Dr. Robert Bindschadler, a glaciologist at Goddard. ''It may be only now that Antarctica is getting around to its full-fledged response to that.''

Almost at the same time of Larsen B's demise, further to the south, an iceberg the size of Delaware broke off the floating part of the Thwaites Glacier. A few months earlier, parts of the Ross Ice Shelf broke off. But these two events, scientists say, are not unusual. As glaciers flow into the water, the ice shelves grow until some point when a large iceberg breaks off, and then the process is repeated. The part of the Ross Ice Shelf where the iceberg broke away is now the same smaller size it was when the explorers Robert F. Scott and Ernest Shackleton observed it at the start of the 20th century.

Oh dear, the Ross Shelf is back to the size it was 100 years ago? How do you explain this?

I can also point you here. Now here's a funny thing, your link says

The Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, and the Jones Ice Shelf collapses also underscore the unprecedented warming in this region of Antarctica.

Unprecedented? No, not really. My link says (and I'd take a published paper over a press release any day of the week) that the Prince Gustav Channel Ice Sheet didn't exist 2,000 years ago and the Larsen A collapsed previously 1.4, 2.1 and 3.8 thousand years BP. Further south and sort of behind the Wilkins is the George VI Ice Shelf. This ice shelf is present now, but not 9595-

7945 cal yr BP. Presumably the Wilkins (being further North) wasn't there either.

 

Something for you to consider. Ice Shelves are fed by glaciers, you know, big moving rivers of ice. If the shelves didn't melt, calve icebergs or similarly disappear, eventually they would make it to the equator and the world would freeze. This would be bad.

 

Ice Shelves have formed and collapsed without any help from man for who knows how long, in a purely natural fashion. You want to point to this one? Fine, but prove the connection.

 

As an aside, I noticed an interesting thing in the linked absract. The Larsen B which collapsed in 2002 had remained solid during the Holocene even though the George VI on the other side of the peninsula and further South did. It would appear that the two sides have (or had) very dissimilar climates.

 

Second aside. I came across a story (but lost the link) referring to a different sheet in the Northern Hemisphere which was located "South of the North Pole". You just gotta love journos.

[DrP]

What is the normal sort of size of ice shelf break up during the anual spring thaw?? It'd be interesting to find out - as JohnB said - this does happen all the time, every year during the spring thaw.

[Chris C]

Right after the denial community informs the scientists that CO2 lags temperature, and we have a sun, and we had mid-century cooling when emissions were going up, and how cosmic rays resolve the faint young sun and snowball earth, and the other standard list of claims, they can then inform the scientists that ice melts!! But since it happens "all the time" why such media attention?? Is it a conspiracy by the eco-nazi alarmists to sensationalize everything?? Probably not...more like the event, like Larson B a few years ago, and another one a few years before that, are not every year events. It is also quite interesting for scientists to see rather rare events.

 

Maybe because the *trends* are toward ice decline on interannual to decadal timescales. I've heard junk like how ice grows and regrows all the time, but those that understand bascule's graph will appreciate the secular trend in our warming climate.

[Pangloss]

Read harder, Homer:

 

What is this, the school yard? Knock it off.

 

You set yourself up for reasonable criticisms by turning this into a straw man in the OP:

 

Despite allegations by the climate change denialist blogosphere that everything's fine and dandy down in the Antarctic, 220 square miles of an Antarctic ice shelf has broken up and collapsed into the ocean, with an additional 5,282 square miles, comparable to the state of Connecticut or about half the area of Scotland, also on the verge of breakup.

[iNow]

Reasonable criticisms welcomed. Regurgitated nonsense shunned. Fair?

[JohnB]

ChrisC,

Is it a conspiracy by the eco-nazi alarmists to sensationalize everything?? Probably not...more like the event, like Larson B a few years ago, and another one a few years before that, are not every year events. It is also quite interesting for scientists to see rather rare events.

That must be record. Only 9 posts in and the "N" word rears it's head. No-one suggested a conspiracy of any type. I was pointing out that just because something hasn't happened in the last 100 years or so, doesn't immediately link the occurrence to AGW.

Maybe because the *trends* are toward ice decline on interannual to decadal timescales.

AFAIK, no-one disputes the trends, it's the interpretation. Global climate changes all the time. To just make the statement of fact "The 20th century was warmer than the 18th and 19th" is silly. Of course it was, any century in something called a "Little Ice Age" will be colder than ones that are not. Moreover, it is only logical that the particular century following the end of such a period must show a trend of increasing temperature. The statement of fact is as meaningless as stating "Winter is colder than Summer".

we had mid-century cooling when emissions were going up

Yes we did, and we all know the answer to that one. Aerosols. But Sceptical Science was asked 4 months ago if they could provide a single paper to back up the aerosol theory and have yet to respond. Intuitively it seems right and in some papers I've read it is mentioned as an explanation for mid century cooling, but I've never seen a paper cited in that regard. Do you know of any? (I'm not trying to put you on the spot, it's just I've been looking and can't find any, so any help would be appreciated.) The idea of aerosols being responsible seems to have become accepted lore without actually being proven.

[bascule]

You set yourself up for reasonable criticisms by turning this into a straw man in the OP:

Despite allegations by the climate change denialist blogosphere that everything's fine and dandy down in the Antarctic...

 

Strawman? Of who? This guy?

 

http://arclightzero.wordpress.com/2007/11/08/convenient-lies-in-the-pop-culture-environmental-movement/

 

For instance, let’s look at the Antarctica issue. Gore, the media and the followers claim that Antarctica is melting away. But just what is the truth?

 

“Gore gives the impression that all of Antarctica, including the East Antarctic Ice Sheet (EAIS), is losing ice mass. In fact, almost all the ice loss observed by Velicogna and Wahr comes from the smaller West Antarctic ice sheet (WAIS). Gore neglects to mention that the study looked at only three years of data—from mid-2002 to mid-2005…

 

Two other recent studies—both from 2006—also indicate a positive mass balance in Antarctica. Chen et al. found that, during April 2002 to November 2005, ice mass gains in the EAIS exceeded ice mass losses in the WAIS. Wingham et al. found that, during 1992-2003, mass gains from accumulating snow on the Antarctic Peninsula and within East Antarctica exceeded ice mass loss in West Antarctica.”

 

But wait, Al Gore, NBC, and the environmental zealots are telling us that Antarctica is melting and that sea levels will rise! Is this just selective reporting, or is it just a conspiracy by other scientists to detract us from the truth?

 

(emphasis added by the author)

 

Can you stop bandying around terms like "strawman" where they aren't applicable?

 

Yes we did, and we all know the answer to that one. Aerosols. But Sceptical Science was asked 4 months ago if they could provide a single paper to back up the aerosol theory and have yet to respond. Intuitively it seems right and in some papers I've read it is mentioned as an explanation for mid century cooling, but I've never seen a paper cited in that regard. Do you know of any?

 

Try this one: Effect of carbonaceous aerosols on surface temperature in the mid twentieth century

 

Also this one: Combinations of Natural and Anthropogenic Forcings in Twentieth-Century Climate

 

Here's a plot of the radiative forcing inputs used by their model:

 

 

Notice a drop in sulfate associated with mid-20th century cooling. Note: This isn't a correlation implies causation fallacy. The radiative forcings are inputs to the model i.e. the "hypothesis", although it's one based on considerable science in and of itself. A successful reconstruction of the historical record is what gives this set of inputs credence.

[JohnB]

Bascule, thanks for those links. (Pity the first is an abstract but I hope to find the full paper soon.)

 

The problem I have with "model" papers is the distinct lack of reference to reality. I have yet to see one that quantifies the sulfate levels.

 

The following is not an attempt to disprove the paper by argument from absurdity, but an attempt to explain the area I have problems with this type of paper.

 

Suppose I had a hypothesis that migrating sea gulls had a negative forcing, what with all the light being reflected off their wings. I then postulate that the number of migrating sea gulls increased from 1940-1970 and then dropped off again.

 

I could (theoretically) feed this information into the GCM used in the second paper and get a good correllation with the observed temp readings. However this would prove nothing unless I could also come up with quantitative figures to show that the number of migrating sea gulls actually did increase and decline in a manner that would give the correct forcings.

 

If a paper came out with this hypothesis, my first reaction, and I'm sure the reaction of everbody here would be to say "Show us the numbers for migrating sea gulls as an annual plot and then we might believe you have based your calculations in reality."

 

What the second paper doesn't do, nor do any others that I've seen, is "show me the sea gulls".

 

I want to see the correllation between actual amounts of recorded sulfates and their forcings. That is the step that appears to be missing.

 

Using a linear addition as the second paper does. FA+FB+FC+FD= delta T, (Which is not something I have a problem as a first approximation) I can use almost any values and modify them to fit the final answer. I need to show quantitively that FA, FB, FC, and FD have a proven grounding in the real world values.

 

We can, to a great degree work out the forcings for CO₂, Ozone, Volcanoes and Solar. Where are the figures for particulate pollutants quantified to show that the assumed forcings over time are correct?

 

There is a dip in the temp record from 1940-1970 followed by a rise. We can't just adjust the forcings for aerosols so that the temp curve matches and say we've got it right. We have to show that there was an increase and decrease in aerosols in a quantitative way.

Notice a drop in sulfate associated with mid-20th century cooling.

I assume this is a typo. Aside from a drop in sulfate forcing around 1940, your graph shows a constantly increasing negative forcing due to sulfates from circa 1945 to the present. If your argument is that temps increased from 1970- present due to a decrease in the negative forcing of sulfate aerosols, your graph doesn't show it.