New Study on the Larsen B Ice Shelf Collapse in 2002
11.02.2008 - Other
Using satellite images, scientists from the National Snow and Ice Data Center (NSIDC) and the Aberystwyth University provided a detailed structural glaciological analysis of changes in surface structures on the Larsen B ice shelf before its collapse in 2002. According to this study, ponded meltwater is not the only culprit. Many other factors are to be taken into account, particularly the weakening of structural glaciological discontinuities. The original paper is available online on the Journal of Glaciology website (PDF format).
The former Larsen B ice-shelf consisted of 4 different flow units fed by various glaciers. Between these were suture zones where the ice was thinner. The collapse itself might have been initiated by perturbations in the input velocity from one or more of the tributary glaciers flow units, causing the sutures to rupture and leading to the rapid disintegration of the ice-shelf. Observed loss of ice at the front of the ice shelf probably played a role as well, since it's there that laid the strongest portions of the shelf, where accumulation created thicker suture zones.
Even if this hypothesis is correct, a trigger is still required for such a sudden and rapid disintegration to occur. The theory is that ponded meltwater on the ice-shelf surface acted as a mechanical force in the crevasses, accelerating ice shelf disintegration. The warming of deep Southern Ocean currents, which increasingly brush against the Antarctic coastline are another thinning factor. The unusually warm summer of 2002, part of a multi-decade trend of warming clearly tied to climate change, struck the final blow.
The presence of large offshore open-rifts systems is also something to be considered. These rifts are a relatively recent characteristic of the ice shelf (less than 20 years old). It has been found that they became more pronounced during the few years preceding the break-up. The blocs of ice found in these rifts rotated because of the strong lateral shear in the zone separating active and less-active flow units. When Larsen B collapsed, disintegration proceeded as far back as these rifts.
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