Further break-up of Wilkins Ice Shelf

Wilkins Ice Shelf is located on the western side of the Antarctic Peninsula at about 70°S, about 100km south of the southern tip of South America. Dr. Angelika Humbert of the Polar Geophysics Research Group of the University of Muenster and her colleague Dr. Matthias Braun of the Center for Remote Sensing of Land Surfaces of the University of Bonn have monitored the events, which started on 30 May 2008.

The team of researchers is tracking the development in a sensitive region, which connect the Wilkins Ice Shelf to Charcot and Latady Islands, since years by means of satellite images of the European Space Agency (ESA) and the German Aerospace Center (DLR).

The formerly about 15 km wide connection between the islands was reduced in its width to now only about 3 km. Satellite images show on the remaining ice plate an arched fracture, making it most likely that the remaining plate will disrupt completely in the next few days. The consequences for the entire ice shelf are not yet foreseeable.

The newly broken up ice mass was already a year ago littered with small fractures. 'The real damage was done already then' is Angelika Humbert pointing up, who already reported with her colleague about the reasons for the fracturing: buoyancy forces due to different ice thicknesses caused bending stresses in the ice. These led to fractures, which spread abruptly.

Subsequently, the unstable ice is breaking at a later point – as it happened the second time in a few month. Ice shelves on the Antarctic Peninsula are floating on the sea and are sandwiched between a warming ocean and increasing surface air temperatures. A possible connection to the extraordinary warming rates observed along the Antarctic Peninsula may exist by promoting melting processes on the underside of the ice.

The recent break-up shows that melt water, which was long in believed to cause as solely factor ice shelf break-up, played no role in the recent event: in the current Antarctic winter the surface of the Wilkins Ice Shelf is frozen completely.At the moment, the largest stresses in the ice are likely due to ice creep, the deformation of ice under its own weight. These stresses might have drawn the fracture faces apart and caused them to cut through. The break-up was running this time completely different from the February 2008 event: while that time the icebergs were calving directly from the ice front, this time the ice mass is breaking up from the inside out. Small sliver icebergs capsize and push the ice mass in front of it outside.