Sunday, 8 January 2017

Antarctica Larson C ice shelf close to becoming one of biggest icebergs ever - or not

Really? The entire ice shelf? It must be true, if the Christian Science Monitor says so:
Antarctica's Larson C shelf is about equal to the area to the state of Delaware. Its collapse might be imminent. 
JANUARY 6, 2017 —Scientists with the British Antarctic Survey now believe that the fracturing of the Larson C ice shelf from the polar cap is imminent, after a rift in the shelf grew vertiginously in the last month of 2016. 
The thread connecting Larson C to the rest of Antarctica is now just more than 65,600 feet long, surveyors from the Britain’s Project Midas say. 
Apart from the ice shelf being about equal in area to Delaware, not one of the statements is correct. They're not simply misquotes. The BAS scientists believe nothing of the kind - their article is titled Giant iceberg set to calve from Larsen C Ice Shelf, and that the calving is imminent. Surveyors from Britain’s Project Midas believe nothing of the kind either. They wrote: (my bold)
Larsen C Ice Shelf poised to calve
The Larsen C Ice shelf in Antarctica is primed to shed an area of more than 5000 sq. km following further substantial rift growth. After a few months of steady, incremental advance since the last event, the rift grew suddenly by a further 18 km during the second half of December 2016. Only a final 20 km of ice now connects an iceberg one quarter the size of Wales to its parent ice shelf.
No one but a moron could fail to grasp what those articles stated and meant. CSM author David Iaconangelo clearly isn't a moron, but is what might be euphemistically termed "economical with the truth".

Grist isn't much better - an editor retitles a "cross-post" and reorders images with captions removed to give a very different impression to the linked Climate Central article.

"Antarctica’s fourth biggest ice shelf is on the verge of collapse" shrieks Grist. However, the picture at the top of the page

.... is of the Larsen B disintegration in 2002. There's no caption, nor is it referred to in the text. Below the author's name is stated "Cross-posted from Climate Central". That link is to the article by CC author Andrea Thompson, titled Large Iceberg Poised to Break Off From Antarctica. Does she, or any of her quoted sources think "Antarctica’s fourth biggest ice shelf is on the verge of collapse"? No, this is just Grist once again changing a word or two, or misquoting a link or two, to push its catastrophic view of anything that might be remotely connected to what they think is the coming apocalypse. Also, that picture has been cropped to remove a distance scale at the bottom, as the Larsen B was about the size of the piece splitting from Larsen C. The scale might give the game away.  The one in the CC article, is captioned quite correctly The breakup of Antarctica's Larsen B ice shelf as it looked on Feb. 23, 2002. Click image to enlarge. Credit: NASA
The breakup of Antarctica's Larsen B ice shelf as it looked on Feb. 23, 2002.
Click image to enlarge. Credit: NASA

It's not a "cross-post" - Grist has altered the title, removed image captions, and reordered images from the CC article, to create the impression that the images are of Larsen C. Removing captions, editing images, and showing them out of context to create an impression not intended by the original author is more than breaking the rules of attribution, it's fraud.

Unusually, I find the CC article generally factual, informative, and links back up the text, though there are one or two disputed claims.

Author Andrea Thompson headed her article with this close-up image of part of the rift:
A large rift in Antarctica's Larsen C ice shelf, photographed by NASA's IceBridge mission on Nov. 10, 2016. The rift surged ahead by about 10 miles in late December.
Click image to enlarge. Credit: NASA/John Sonntag

In the Grist "cross-post", that image follows a a paragraph about the disintegration of Larsen B, and has the caption "NASA". The intention is now obvious, and totally unforgivable.

On a more factual note, the rift is about 500m (metres, not miles) wide, 350m deep in the centre, and is currently about 80km long, according to Project MIDAS. Some articles say 80 miles, and if the scale on the graphic below, is accurate, 150 km would be more like it. Not that it matters to you maybe, but I'll check. It's not unusual for genuine mistakes to go unnoticed by authors:
Source: Project MIDAS

The graphic is of more than a little personal significance - I was born just about where the second "s" in Swansea is located top right (although Wales is a little further north, and a lot warmer than its position on that graphic.

I've read a few articles that say words to the effect that the rift has just been discovered (where did they get that?), but it's been monitored since 2011.

Even the BBC managed to get it right:

Huge Antarctic iceberg poised to break away 
An iceberg expected to be one of the 10 largest ever recorded is ready to break away from Antarctica, scientists say. A long-running rift in the Larsen C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5,000 sq km piece from floating away.
Larsen C is the most northern major ice shelf in Antarctica.
Researchers based in Swansea say the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up.
Larsen C is about 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.
Researchers have been tracking the rift in Larsen C for many years, watching it with some trepidation after the collapse of Larsen A ice shelf in 1995 and the sudden break-up of the Larsen B shelf in 2002.
They even end the piece with
"We are convinced, although others are not, that the remaining ice shelf will be less stable than the present one," said Prof Luckman.
"We would expect in the ensuing months to years further calving events, and maybe an eventual collapse - but it's a very hard thing to predict, and our models say it will be less stable; not that it will immediately collapse or anything like that."
As it floats on the sea, the resulting iceberg from the shelf will not raise sea levels. But if the shelf breaks up even more, it could result in glaciers that flow off the land behind it to speed up their passage towards the ocean. This non-floating ice would have an impact on sea levels.
According to estimates, if all the ice that the Larsen C shelf currently holds back entered the sea, global waters would rise by 10cm.
All that is very much in the future. There are few certainties right now apart from an imminent change to the outline of Antarctica's icy coast.
"The eventual consequences might be the ice shelf collapsing in years to decades," said Prof Luckman,
"Even the sea level contribution of this area is not on anybody's radar; it's just a big geographical event that will change the landscape there."
Prof. Luckman is one of the Project MIDAS team, based in Swansea. I like very much "We are convinced, although others are not...". It shows some humility, the acknowledgement that it's a personal team view. A good note to end on.

UPDATE 10/1/2017

I've been scanning through articles on the British Antarctic Survey website. I've always thought
the BAS to be a reactionary and somewhat alarmist bunch. I had already noticed this, on the page referenced above:
Glaciologist Professor David Vaughan OBE, Director of Science at British Antarctic Survey, said, “The calving of this large iceberg could be the first step of the collapse of Larsen C ice shelf, which would result in the disintegration of a huge area of ice into a number of icebergs and smaller fragments.
“Because of the uncertainty surrounding the stability of the Larsen C ice shelf, we chose not to camp on the ice this season.  Researchers can now only do day trips from our Rothera Research Station with an aircraft nearby on standby.”
In 2015 they said this:
The team, who continue to monitor the ice shelf closely, predict that a collapse could occur within a century, although maybe sooner and with little warning. A crack is forming in the ice which could cause it to retreat back further than previously observed. The ice shelf appears also to be detaching from a small island called Bawden Ice Rise at its northern edge.
"Within a century" - what's changed in the 19 months since that statement? Prof. Vaughan has dramatically changed his view - back in 2015:
Professor David Vaughan, glaciologist and Director of Science at BAS, says:
“When Larsen A and B were lost, the glaciers behind them accelerated and they are now contributing a significant fraction of the sea-level rise from the whole of Antarctica. Larsen C is bigger and if it were to be lost in the next few decades then it would actually add to the projections of sea-level rise by 2100.
On the same page - "within a century" and "the next few decades". However, contradictions like this aren't unusual on the BAS website. Members have very differing views, and careful reading reveals very different "facts" too. The thickness of the Larsen B shelf, which disintegrated in 2002, is given as 200 metres, and on one page a very unlikely and obviously incorrect 1km. That last article I quoted, actually a press release titled New study shows Antarctic ice shelf is thinning from above and below has this lead-in:
The Larsen C Ice Shelf — whose neighbours Larsen A and B, collapsed in 1995 and 2002 — is thinning from both its surface and beneath. For years scientists have been unable to determine whether it is warming air temperatures or warmer ocean currents that were causing the Antarctic Peninsula’s floating ice shelves to lose volume and become more vulnerable to collapse. This new study takes an important step forward in assessing Antarctica’s likely contribution to future sea-level rise. 
The research team combined satellite data and eight radar surveys captured during a 15-year period from 1998–2012. They found that Larsen C Ice Shelf lost an average of 4 metres of ice, and had lowered by an average of one metre at the surface. 
Lead author, Dr Paul Holland from British Antarctic Survey (BAS), says:
“What’s exciting about this study is we now know that two different processes are causing Larsen C to thin and become less stable. Air is being lost from the top layer of snow (called the firn), which is becoming more compacted — probably because of increased melting by a warmer atmosphere. We know also that Larsen C is losing ice, probably from warmer ocean currents or changing ice flow. 
“If this vast ice shelf — which is over two and a half times the size of Wales and 10 times bigger than Larsen B — was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise.”
The Antarctic Peninsula is one of the fastest warming regions on Earth, with a temperature rise of 2.5°C over the last 50 years.
"Air is being lost", "probably because of increased melting by a warmer atmosphere". Here's a plot of the "warmer atmosphere" since 1995:
Larsen C - GISS unadjusted data.

I don't think so. What's amazing, is that many glaciologists and climate scientists never keep up-to-date with the latest data, but rely on published papers, many of which are out of date within a few years. I read something a dated a few weeks ago by a glaciologist, publishing regularly in this field, who cited "the continuing warming on the Antarctic Peninsula". An Ostrich is a large flightless bird, claimed to occasionally put its head in the sand. Some scientists are sightless birds, with their heads continually in the sand. More on the "continued warming" (/sarc off) soon.

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