By N.F. Glasser and T.A. Scambos

Global warming may not be entirely to blame for the collapse of an Antarctic ice shelf in 2002, according to research published today. The 10,000-year-old Larsen B ice shelf was initially believed to be a victim of climate change. But a paper published in the Journal of Glaciology claims the shelf had been teetering on collapse for decades. Professor Neil Glasser, of Aberystwyth University, the paper’s lead author, said cracks and fault lines in the ice had significantly weakened the structure. “A number of other atmospheric, oceanic and glaciological factors are involved. For example, the location and spacing of fractures on the ice shelf such as crevasses and rifts are very important too because they determine how strong or weak the ice shelf is.”

From their abstract: We define domains on the ice shelf related to glacier source areas and demonstrate that, prior to collapse, the central Larsen B ice shelf consisted of four sutured flow units fed by Crane, Jorum, Punchbowl and Hektoria/Green/Evans glaciers. Between these flow units were ‘suture zones’ of thinner ice where the feeder glaciers merged. Prior to collapse, large open-rift systems were present offshore of Foyn Point and Cape Disappointment. These rifts became more pronounced in the years preceding break-up, and ice blocks in the rifts rotated because of the strong lateral shear in this zone. We suggest that the ice shelf was preconditioned to collapse by partial rupturing of the sutures between flow units.  See full paper here.

Icecap Note: The breakdown in 2002 as the authors showed may have had its seeds in antecedent conditions which affected the ice-shelf’s structure and stability. A factor that may be pertinent to the timing of that break-up was the high solar flux, second solar cycle max that occurred from September 2001 to April 2002. Notice in the image below the coincident timing of the high flux and ice decline.