Cracking up


With the “pin” to Charcot Island gone, big cracks that first formed in 2008 are are opening up in the Wilkins ice shelf, and a new break up is taking place close to Latady Island. The animation above uses ESA “webcam from space” images captured on April 18 and 21 (the latter has black corners). Latady Island is bottom left. Judging by the scale on the NASA image below, the big crack above bottom right has opened up by a couple of kilometres, and the whole assemblage of chunks of shelf are moving northwards. It’ll be interesting to see if new cracks form deeper into the shelf (bottom right) as the new bergs move away. Meanwhile, NASA’s Earth Observatory helpfully provides a new photo-like image of what was the base of the ice bridge, captured by the Terra satellite on April 12:


And while we’re on the subject of ice, the Earth Observatory has just posted an excellent new feature article on sea ice, covering both ends of the planet and illustrated with some spectacular imagery. Well worth a read for anyone wanting an in-depth introduction to the state of play before the Arctic melt season really gets underway.

[Nick Lowe]



This somewhat crude(*), but effective animation of the two most recent ESA images of the Wilkins Ice Shelf break up shows clearly that with the “pin” gone, large areas of ice are beginning to move. The most recent image (April 8th) is the smaller, overlaid on one captured on April 5th. Focus on what was the narrowest part of the ice “bridge” to Charcot Island, and you can see a large berg rotating counterclockwise, while the mass of shattered ice at the original break up site and three big bergs to the east appear to be moving slowly north. To the NE of the base of the “bridge”, cracks are getting wider, while there’s also substantial northward movement in the big bergs to the north and east left by earlier collapses. It’s not clear from this pair of images what’s going on in the biggest cracks running SW/NE below the base of the “bridge”, but that will be the region to watch for the next big breaks.

[* What do you expect? GR fecit…]

Gone west


NASA’s Earth Observatory has just published a pair of beautiful images of the Wilkins Ice Shelf showing the ice bridge before and after collapse. The image above, acquired on April 6th, shows the bergs created by the break up moving towards the west. With the bridge gone, the remnant ice from earlier break ups to the east is now free to follow those bergs out to sea.



Since I posted 12 hours ago on the imminent demise of a large chunk of the Wilkins ice shelf, new ESA imagery shows that it has finally collapsed into a shattered mass of icebergs — roughly centre of this image. The BBC has the story, together with comments from David Vaughan of the British Antarctic Survey. Loss of this “pin” could destabilise even more of the shelf — look at the large cracks bottom right…

[Update: see also Times Online, and the DomPost story has this quote from Prof Tim Naish of VUW’s Antarctic Research Centre: “It’s a consequence of global warming. Antarctica is behaving in a very strange way, bits of it are cooling and bits of it are warming. Our deep time records tell us that these ice shelves are the early warning signals; when they go, then we see quite dramatic and unstable changes in the ice sheets and glaciers feeding them.”

There have been a lot of new units of area invoked: Wilkins is as big as Connecticut, Jamaica, and almost half the size of Wales. But which half? Is Cardiff safe? 😉 ]

Last straw


The last bit of the ice “bridge” pinning the Wilkins Ice Shelf in place appears to be on the verge of collapse, according to the European Space Agency. New rifts formed on April 2nd (blue lines above), and have begun to spread rapidly. Worth keeping an eye on the ESA’s “webcam from space” over the next few days…

[Tip of the hat to Cindy in Bonn]

[Robert Wyatt]