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Friday, July 14, 2017

Gigantic ice block, A-68, impressed Anthony Watts so much he came back from his holiday from @wattsupwiththat

Sou | 3:42 PM Go to the first of 19 comments. Add a comment
Photo: John Sonntag, NASA
Most of you will by now have heard that the cracked ice shelf on Larsen C has split the whole way through. This means a gigantic block of ice is now floating free. It's got a name as bland as all the other recorded icebergs: A-68.

The block measures about 5,800 km² in area and weighs more than a trillion tonnes. It is one of the ten biggest icebergs ever recorded.  The weight is equivalent to the weight of 7,142,857,143 fully grown blue whales, the world's largest mammal.  To visualise the area, think of somewhere that's 29 km by 200 km or 18 by 124 miles. The iceberg is around the same size as Australia's largest island after Tasmania, Melville Island north of Darwin, which is 5,786 km² in area.



There's an article at Quartz by Zoë Schlanger, Jennifer Brown and Katherine Ellen Foley, with some other international comparisons, for example, it covers an area twice as big as the Australian Capital Territory and 60 times the area of Paris.

This isn't the largest iceberg ever. The largest recently recorded is B-15, which split off from the Ross Ice Shelf in Antarctica 17 years ago, in March 2000. It was almost twice the size of this one, measuring 295 km (183 miles) by 37 km (23 miles), and having a surface area of 11,000 km² (4,200 sq miles). Wikipedia also lists other recent large icebergs - here and here.

After the split at Larsen C, the ice shelf went from being the fourth largest in the world to the fifth.

The surface is only part of it. With a volume of 1155 cubic km (277 cubic miles), most of the iceberg is below the surface. Brian L. Kahn has put together some images over at Climate Central, to help you visualise how big the volume of this iceberg is.




It's natural, but happening in a time of global warming


The initial part of the crack had been there for a very long time. Adrian Luckman, at the Conversation, said that it was observed from satellites as a well-established rift way back in the 1980s but appeared to be fairly stable until January 2016, when it started to extend very quickly. The animation below is downsized from one put together by Project MIDAS, an Antarctic research consortium led by Swansea University in the UK. The animation uses radar images from the Copernicus Sentinel-1 mission.  The original can be viewed on the European Space Agency website:



This split is considered a natural event. The way global warming could have contributed would have been from warmer oceans under the ice shelf, but I've only read mild speculation about that. Most of the experts just seem to regard it as something that happens to ice sheets. (I did come across an interesting article by Roz Pidcock at Carbon Brief, about work by Prof Bryn Hubbard.)

That's not to say that this event, happening as it does in a time of climate change, won't lead to changes that wouldn't have occurred in cooler times. After chunks of ice split off from the smaller neighbouring ice shelves Larsen A and Larsen B, the whole shelves began to collapse, meaning the ice sheets have no ice shelves to slow their progress into the sea. Well-known Antarctic researcher, Eric Rignot, and the British Antarctic Survey, put together a graphic for Chris Mooney at the Washington Post, showing how this break, and the collapse of Larsen A and B, have changed the coastline of Western Antarctica.
Below is a very short video about Larson B, narrated by Ala Khazendar of NASA's Jet Propulsion Laboratory (JPL). You can read about this on the NASA JPL website:




Larsen C has been thickening lately so whether it will suffer the same fate as Larsen A and B won't be known for some time, according to Adrian Luckman, who also wrote:
Even if the remaining part of Larsen C were to eventually collapse, many years into the future, the potential sea level rise is quite modest. Taking into account only the catchments of glaciers flowing into Larsen C, the total, even after decades, will probably be less than a centimetre.

Anthony Watts was so bored by the affair...


Anthony Watts was so bored by the affair, he thought it so insignificant, that he made the effort to write his one and only article since he went on his holiday. Yes. That's right. He thought it such a yawn that it warranted him coming back to work.

In an article with the headline "Media gets high on Antarctic Crack" (archived here), Anthony wrote the strawman:
Just because we can see changes happening on the most remote region of our planet in exquisite detail for the first time in the history of mankind doesn’t necessarily mean those changes are unprecedented. 
It's a strawman because I've not seen anyone say that calving from ice sheets is unprecedented, or that this particular calving was unprecedented. All the articles that Anthony referred to, including those he copied and pasted, were informative, not "alarmist". Unlike Anthony, the reporters did their research and asked the experts about the event.

Anthony finished his part of his article with this:
I can’t get too worked up about this, even though the usual suspects are. Back to R&R, Ta – Anthony
Well, he did get sufficiently worked up to come out of hiding for the first time to write about it.


From the WUWT comments



There were quite a few comments from people who were surprised about the reporting from the BBC, CNN, the Weather Channel and more - that the reports did not attribute the break to global warming. In other words, though no-one was dumb enough to say it out loud to Anthony's face, some people know that Anthony's take was one giant strawman. There were also some gems.


Does tmitsss really think it's now summer in the southern hemisphere?
July 13, 2017 at 7:35 am
That this is happening at the height of summer is proof enough for me that this connected to global warming. Think of the poor polar bears!

Peter Plail compares the size of the iceberg with that of the entire Antarctic continent. I expect he'd argue that the Grand Canyon is miniscule, using the same comparison.
July 13, 2017 at 8:55 am
Or to put another way, it is miniscule in comparison with the totallity of Antarctica.

andrewmharding hopes Anthony gets better soon. He also mixes up his ice sheets with his ice shelves and blames the crack on volcanoes. As well as that, he builds on a strawman, and thinks that the greenhouse effect only works in summertime :)
July 13, 2017 at 8:12 am
Hi Anthony, good article, hope you are on the mend. The media dare not unduly blame AGW for this, it was well known for years that this event would happen due to geological activity melting the ice under the ice sheet undermining it significantly. The fact that this has happened in the Antarctic winter would make anyone with intelligence realise that CO2 was not to blame.

CheshireRed admits that none of the articles attribute the break in the ice sheet to human activity, however he just knows that they want to. "It's there for all to see." he writes. Even though they "don't specifically say so". It's a (hidden) conspiracy! Sad.
July 13, 2017 at 8:20 am
A lot of subtle double-speak going on from the usual suspects. They ALL know this is a perfectly normal event yet slyly allude to some sort of human influence, even if they don’t specifically say so. It’s there for all to see. If they can’t be unambiguously honest about this incident – and they’ve shown they can’t, what hope is there that they’ll clean up their act for the future? I’d say about zero. Sad. 

brian stratford believes the unbelievable. I mean the ice shelf that broke is more than 12,000 years old. There are ice cores from Antarctica that have ice that's 800,000 years old, and scientists are now hoping to drill to ice dating back 1.5 million years:
July 13, 2017 at 2:57 pm
According to old maps the continent of Antarctica was ice free only 6000 years ago. Piri Reis for example. 

References and further reading


I've picked out some of the most informative articles on the break, and included one from Roz Pidcock at the Carbon Brief, from a year ago that might interest you.

Sentinel satellite captures birth of behemoth iceberg - article from the European Space Agency, July 2017

I’ve studied Larsen C and its giant iceberg for years – it’s not a simple story of climate change - article by Antarctic researcher, Adrian Luckman, at The Conversation, 12 July 2017

An Iceberg the Size of Delaware Just Broke Away From Antarctica - article by Jugal K. Patel and Justin Gillis at the New York Times, 9 July 2017

Iceberg twice size of Luxembourg breaks off Antarctic ice shelf - article by Nicola Davis at The Guardian, 12 July 2017

Antarctica shed a block of ice the size of Delaware, but scientists think the real disaster could be decades away - article by Sean Greene at the LA Times, 13 July 2017

Two Luxembourgs, 10 Madrids, one Delaware: How a giant iceberg is described around the world - article by Zoë Schlanger, Jennifer Brown and Katherine Ellen Foley at Quartz, 12 July 2017

Scientists have unearthed a 100m-thick river of ice beneath Antarctica’s Larsen C ice shelf, which they fear could accelerate its path to eventual collapse - article by Roz Pidcock at The Carbon Brief, from June last year - 14 June 2016

NASA Study Shows Antarctica’s Larsen B Ice Shelf Nearing Its Final Act - article by Steve Cole and Alan Buis of NASA, 15 May 2015




19 comments:

  1. I suspect Anthony wrote the article because he felt the need for a squirrel to distract from Trump's wavering in Paris. Poor Eric - who predicted other countries would follow Trump's "leadership" - will provide more.

    ReplyDelete
    Replies
    1. I'm afraid Trump just reflects the last person to have his ear, so nothing more will be heard of it after he gets home. Then again, it's a bold soul who predicts anything these days.

      Delete
  2. 1mm of sea level rise is a volume increase of 360 cubic km, 360 billion tons.

    Sea ice is rising 3.2mm/year.

    A-68 is already floating, so will not affect sea level.It I a good way of visualising the problem.

    It is the equivalent of a year's sea level rise in one lump.

    ReplyDelete
    Replies
    1. Yep - shows how huge it is.

      Because it's fresh water floating on salt water, it will raise sea level a smidgen. Not as much as if it came off the land. Around 0.1 mm according to Gavin Schmidt.

      Delete
  3. brian stratford

    "According to old maps the continent of Antarctica was ice free only 6000 years ago."

    Wow! That must break the record for the earliest maps by a long way. I assume he was having a joke at WUWTers' expense.

    "Early world maps. The earliest known world maps date to classical antiquity, the oldest examples of the 6th to 5th centuries BCE ..."

    ReplyDelete
    Replies
    1. According to "old maps" America does not exist.

      Delete
    2. Then again, it is probably true to say that no ice was ever seen in Antarctica until the 16th century. Largely because Antarctica wasn't seen.

      Delete
    3. He's probably talking about the maps of the world that God gave Adam and Eve when he kicked them out of the Garden of Eden :)

      Delete
  4. It takes less than nine days with the recent global energy imbalance to melt this iceberg (if my assumptions and math are right).

    (Gavin Schmidt tweeted 0.2% of 10 years imbalance, so my figures are definitely in the ballpark)

    ReplyDelete
    Replies
    1. I'm not sure of what you are saying, OlofR. (It will take quite a bit longer than nine days for this thing to melt.)

      Are you saying that if all the current energy imbalance was focused on this iceberg it would melt in 9 days?

      Delete
    2. Yes, the energy needed to melt the iceberg equals nine days of current energy imbalance (approximately).

      Delete
    3. Or more than five million Hiroshima bombs, if those units of energy are more comprehensible.. ;-)

      Delete
  5. The issue that deniers need to keep in mind isn't the fact of giant berg calving, but the frequency of it. And a corollary is the knock-on effect of that impoundment loss at the rate at which it's lost.

    It's all about mass balance. And currently there's an imbalance.

    ReplyDelete
  6. tmitsss seems a bit geographically challenged.

    Think of the poor polar bears!

    I am more worried about the Greenland penguin colonies.

    I did notice (well thanks to CBC) that the iceberg is larger than one of our provinces. Prince Edward Island at 5,660 square kilometres and a quick google show the USA's state of Delaware smaller than the iceberg at 5,130 sq. km.

    ReplyDelete
  7. "
    Larsen C has been thickening lately so whether it will suffer the same fate as Larsen A and B won't be known for some time, according to Adrian Luckman, who also wrote:
    Even if the remaining part of Larsen C were to eventually collapse, many years into the future, the potential sea level rise is quite modest. Taking into account only the catchments of glaciers flowing into Larsen C, the total, even after decades, will probably be less than a centimetre."

    This is beyond crazy and I don't understand how nor why this guy write such bullshit. He is argueing like a denier, putting the references upside down, and nobody raises an eyebrow. From the paper published by the very same A. Luckman, we are learning that Larsen is melting from the climate change and that the current geometry of Larsen C is now barely stable, at best. Here :

    https://cronfa.swan.ac.uk/Record/cronfa33179

    A. Luckman and the team are looking at the density of Larsen C. Probably a 'technical paper' and they are not directly demonstrating that Larsen C is melting from warming but they follow others papers demonstrating this (especially Holand 2015 http://www.the-cryosphere.net/9/1005/2015/tc-9-1005-2015.html but also Holland 2011 http://onlinelibrary.wiley.com/doi/10.1029/2011GL047245/abstract or Paolo 2015 http://science.sciencemag.org/content/early/2015/03/25/science.aaa0940 ).

    ReplyDelete
  8. From Holland 2015 " The surface of Larsen C Ice Shelf (LCIS), the largest ice shelf on the peninsula, is lowering. This could be caused by unbalanced ocean melting (ice loss) or enhanced firn melting and compaction (englacial air loss). Using a novel method to analyse eight radar surveys, this study derives separate estimates of ice and air thickness changes during a 15-year period. The uncertainties are considerable, but the primary estimate is that the surveyed lowering (0.066 ± 0.017 m yr−1) is caused by both ice loss (0.28 ± 0.18 m yr−1) and firn-air loss (0.037 ± 0.026 m yr−1). The ice loss is much larger than the air loss, but both contribute approximately equally to the lowering because the ice is floating."
    The aim of the recent paper involving A. Luckman is to refine the measure of Larsen Cair loss. It is a given that Larsen C surface is lowering (not increasing ...) but this lowering is partly du to the loss of air into ice (so the shelf has a higher density and so sinks, hence the lowerig of the surface). But in no way they are demonstrating that Larsen C is gaining mass, quite the contrary! They validated others studies showing that Larsen C surface is lowering from the loss of air but also from loss of ice. The paper aknowledge this budget of Larsen C surface and the ongoing thining...

    And here A. Luckman clearly showed that losing an iceberg of 6000 km2 (what was actually lost) is a worst case scenario and put Larsen C at the limits of stability at best :

    http://www.the-cryosphere.net/9/1223/2015/

    And they are linking to studies about thining of Larsen C and the contributions of global warming!
    Par tous les saints maudits de l'enfer, how this is even remotely possible? How a guy can turn the work of a life upside down??? I understand, there is nothing simple about Larsen C. Measures are spares and difficults, errors margins are wild, the thresold for the stability of Larsen C is not kwnon exactly, etc... But nothing can back the extraordinary bold claims of A. Luckman in this article...

    As a side note Larsen B collapsed in 7 years and this is a collapse. Perpahs 7 years is a long long time for human, and for us a collapse is probably way shorter. But for a glacier, 7 years is an extremly short time frame and saying that losing an ice shelf in 10 years is not an imminent collapse like is impling A. Luckman reveals a profound misunderstanding of what is a glacier and what is its life time. And the use of the word "imminent" in the phrase "imminent collapse" only obscurs its thoughts and means nothing. The lifetime of a glacier is not the lifetime of a human. Rome for example take 150 years approximately to collapse (from emperor Commode in 192 to the fall of Rome in 410 -the deposition of emperor Romulus Augustulus in 476 is not a serious date) but thus is still a "collapse"

    ReplyDelete
  9. P.S Or perhaps he is also trying to argue that latest measures and short-term variability is more important that long term trend; or perhaps that the rift (wich actually start to form in 2014) was able to foresee the future; or perhaps the two combine. But this will only worsen its case, arguing againt its own research and arguing that the most important is not trend. It is absolutely certain that Larsen C thinned significantly from 1994 to 2014 included, that this thinning is definitely linked to warming, and it will be an extraordinary coincidence if the rift -wich start to extend in 2014- was not at least a consequence of all this thinning and warming.

    ReplyDelete
    Replies
    1. Ah, the sentient rift phenomenon! I did my Masters in Riftneurology.

      Anonymous PhD Photoneurology


      Delete

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