Posted by: JohnnyRook | November 28, 2008

Final Wilkins Ice-Sheet Breakup Looms

Antarctica Peninsula Map

The European Space Agency (ESA) announced today that new Envisat Asar photos show new rifts have formed in Antarctica’s Wilkins Ice Shelf. The ice 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. The Wilkins ice shelf is an anomaly that formed from sea ice and has little inflow from the ice sheet, so it’s demise is unlikely to contribute much to movement of the ice sheet. In most cases however, 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 Celsius in 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.

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.

Wilens Ice Shelf before breakup

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 petition. You can see my post on this topic here.

Related posts: From North to South, the Whole Damn World is Melting

Hat Tip to Steve Bloom at Daily Kos for pointing out an error in the original post–since corrected.

Crossposted at Daily Kos


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