Domino effect of chain reaction drainage of surface lakes led to the breakup of Larsen B Ice Shelf in 2002

No mention of “climate change” as the driver for the sudden event.

When the Larsen B Ice Shelf in Antarctica collapsed in 2002, the event appeared to be a sudden response to climate change, and this long, fringing ice shelf in the north west part of the Weddell Sea was assumed to be the latest in a long line of victims of Antarctic summer heat waves linked to Global Warming. Back in 2008 a paper published in the Journal of Glaciology, Prof. Neil Glasser of Aberystwyth University, and Dr Ted Scambos of University of Colorado’s National Snow and Ice Data Center said that the shelf was already teetering on collapse before the final summer. “Ice shelf collapse is not as simple as we first thought,” said Professor Glasser, lead author of the paper. “Because large amounts of meltwater appeared on the ice shelf just before it collapsed, we had always assumed that air temperature increases were to blame. But our new study shows that ice-shelf break up is not controlled simply by climate.

Source: http://www.sciencedaily.com/releases/2008/02/080210100441.htm

Now they have a mechanism with this new paper just published in GRL:

Chain reaction drainage of supraglacial lakes led to breakup of Larsen B Ice Shelf

In 2002, Antarctica’s Larsen B Ice Shelf disintegrated over the course of just a few months. The shelf, which covered more than 3000 square kilometers (1158 square miles) of ice, had been stable for thousands of years before it broke up, and the processes involved in the sudden breakup were not well understood. Before the breakup, there were more than 2700 small supraglacial lakes on top of the ice shelf that had formed as ice melted gradually over the preceding years. Observations indicated that the majority of those lakes drained within the final few days before the ice shelf broke up, but scientists were not certain how that could have happened.

Now, using a simulation of the stresses that the lakes create on the ice shelf, Banwell et al. show that the draining of one supraglacial lake could result in fractures under other lakes, which, in turn, could cause more fractures under more lakes and thus cause numerous lakes to drain, in a chain reaction. The draining of many supraglacial lakes in a short time period ultimately led to the breakup of the entire ice shelf, the authors suggest.

Source: Geophysical Research Letters, doi:10.1002/2013GL057694, 2013 http://onlinelibrary.wiley.com/doi/10.1002/2013GL057694/abstract

Title: Breakup of the Larsen B Ice Shelf triggered by chain reaction drainage of supraglacial lakes

Authors: Alison F. Banwell: Department of Geophysical Sciences, University of Chicago, Chicago, Illinois, USA; and Scott Polar Research Institute, University of Cambridge, Cambridge, UK;

Douglas R. MacAyeal: Department of Geophysical Sciences, University of Chicago, Chicago, Illinois, USA;

Olga V. Sergienko: The Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, New Jersey, USA.

Abstract: The explosive disintegration of the Larsen B Ice Shelf poses two unresolved questions: What process (1) set a horizontal fracture spacing sufficiently small to predispose the subsequent ice shelf fragments to capsize and (2) synchronized the widespread drainage of >2750 supraglacial meltwater lakes observed in the days prior to break up? We answer both questions through analysis of the ice shelf’s elastic flexure response to the supraglacial lakes on the ice shelf prior to break up. By expanding the previously articulated role of lakes beyond mere water reservoirs supporting hydrofracture, we show that lake-induced flexural stresses produce a fracture network with appropriate horizontal spacing to induce capsize-driven breakup. The analysis of flexural stresses suggests that drainage of a single lake can cause neighboring lakes to drain, which, in turn, causes farther removed lakes to drain. Such self-stimulating behavior can account for the sudden, widespread appearance of a fracture system capable of driving explosive break up.

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Figure at left:

Chain reaction drainage of supraglacial lakes. (a) Observed lakes [Glasser and Scambos, ] are represented by circular disks of equal area and constant depth (5 m). The lake found to trigger the drainage of most neighboring lakes is labeled “starter lake.” Colored surrounding lakes indicate those that are induced to drain either directly by the starter lake’s effect on flexure stresses (stage = 1) or indirectly by lakes which are drained at an earlier stage (stage = 2, …, 10). The color of the lake indicates its stage according to the color bar. When the fracture criterion of 70 kPa is evaluated at each lake’s center, a total of 227 lakes are triggered to drain by the starter lake (either directly or indirectly). The radii of colored lakes are drawn at twice the scale to promote visibility. The radii of gray‐shaded lakes, which are not drained as a result of the chain reaction, are drawn at true scale. (b) As in Figure a but with the fracture criterion reduced to 35 kPa.