By John McLean
On 25 March the US National Snow and Ice Data Center (NSIDC) and the British Antarctic Survey (BAS) jointly published a press statement declaring that the Wilkins Ice Shelf “has begun to collapse because of rapid climate change in a fast-warming region of Antarctica.” I’ve looked at relevant public data and I’m undecided whether this statement was a gross exaggeration, an inept interpretation of the evidence or borderline fraud, because I can see nothing about the collapse to indicate that it was anything but a natural event.
Firstly, there were no other reports of recent collapses in this part of the Antarctic during what the end of the (southern) summer melt period. If climate was the major cause then surely we would have seen other instances of ice shelf disintegration, shelves such as the nearby King George IV shelf or the several shelves along the Bellinghausen Sea just 500km to the west. Secondly and more importantly, there is nothing in the observational data to suggest a dramatic recent change in climatic conditions. The NSIDC/BAS press statement, grandly titled “Antarctic Ice Shelf Disintegration Underscores a Warming World”, said “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.” By accident or design that press release omitted some very vital details about that increase, details that show the warming to have very minor effect and that the likely cause of recent temperature change is quite natural.
The Wilkins Ice Shelf is located about half way along the western (i.e. Pacific) side of the Antarctic Peninsula, that tongue of land stretching towards South America and reaching latitudes comparable with central Alaska (or for European readers, the Finnish city of Oulu). The NSIDC photographs of the Wilkins Ice Shelf give a clear indication of the normal cycle of events and show a lot about the collapse. The distinct line indicates the natural boundary of thicker pack ice and thinner sea ice. The area indicated as being reformed appears to be part of an old collapse that sea ice has progressively filled. The ice in this region is rougher than the long-term pack ice.
Image is for January 15, 2008, prior to the partial break-up. See larger image here
A plausible hypothesis is that wind and wave conditions during the second quarter of 2007 caused internal forces that opened an old weakness in the ice. Perhaps that weakness was caused by undercutting wave action back in 2004 and the sea ice has until now had braced the pack ice. The hypothesis of previous bracing is supported by the press statement, which said “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”. One collapse apparently triggered another, which is what we’d expect from bracing. This begs the question of when the Wilkins Ice Shelf last lost ice from its southwestern edge and whether the recent collapse was not some kind of “catch up” of natural processes.
There are many possible causes for this loss of ice, which in itself is hardly a momentous and unknown event, but it seems that neither NSIDC nor BAS were inclined to look beyond the reasons that we all recognize as being likely to interest the news media. If NSIDC or BAS have evidence that the ice shelf collapsed due to man-made warming then they need to produce it very quickly. Until that happens I will continue to believe that their great hype about man-made climate change is no more than a con job. It grabbed some brief media attention but now we can go back to observing falling temperatures and a very poor correlation between temperature and carbon dioxide concentration, two factors that unfortunately for many believers threaten to undermine the claims of man-made warming. See full pdf analysis here.