The European Space Agency (ESA) announced today that new Envisat Asar photos show new rifts have formed in Antarctica's Wilkins Ice Shelf. Theice shelf, which is connected to two islands, Charcot and Latady, is the anchor for the ice sheet behind it. The rifts threaten the stability of the ice shelf which owing to previous breakups this year has been reduced to a narrow finger of ice. For information on the previous breakups see: UPDATE: Bridge to Wilkins Ice Shelf Faces Imminent Collapse
Photo and map above are from the European Space Agency.
The appearance of the rifts is consistent with ice shelf behavior just before a breakup. See: When Ice Shelves Collapse: A Brief Tutorial As the ice shelf is floating, it's collapse will not directly contribute to sea-level rise, but recent research has shown that removal of ice shelves is the major factor contributing to ice sheet movement. Ice shelves serve as stoppers on the movement of the ice sheets behind them. Warming air (the Antarctic ice shelf has warmed 2.5 degree Celsiusin the last 50 years) and warming sea water cause melting of the ice shelf. When the ice shelf, which is anchored to the seabed at its terminus breaks up, the stopper is removed and the ice sheet is free to move. Historically, movement has increased up to 8 times in the wake of ice shelf collapse.
CORRECTION: Although, the above description is true in most instances, as Steve Bloom reminded me in a comment below, the Wilkins ice shelf is an anomaly and unlikely to lead to extensive ice sheet movement. I reprint the relevant part of his comment here.
JR, IIRC the Wilkins is a (relatively rare) type of ice shelf that formed from sea ice, and isn't doing much if any blocking of glaciers. What's alarming about its break-up is that it's the southernmost one so far, and so is one step closer to the much larger ice shelves on the edge of Antarctica proper that in turn hold back the really big ice sheets.
The image below from the National Snow and Ice Data Center shows the ice shelf and Charcot and Latady Islands (between -70 and -71 degrees on the left hand side) before the the earlier breakups this year, which reduced the ice shelf to the narrow finger that it is now.
The Wilkins ice shelf seems unlikely to survive the Antarctic summer which is beginning now. Amazingly, the earlier breakups this year occurred during the Antarctic Winter.
If you are alarmed by this news, (and you should be) allow me to remind you that today is the final day for comments to be made to the EPA on whether it should regulate CO2 as a danger to human health. I would encourage you to follow this direct link and sign the We Campaign's petition. You can see my post on this topic Tell the EPA to Regulate CO2 as a Pollutant (Comment Deadline is Friday).
Related posts: From North to South, the Whole Damn World is Melting
Crossposted at Climaticide Chronicles