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Sea Level Consequences of Exceptional Glacial Meltwater Forcing

Tedstone, A.J., Nienow, P.W., Sole, A.J., Mair, D.W.F., Cowton, T.R., Bartholomew, I.D. and King, M.A. 2013. Greenland ice sheet motion insensitive to exceptional meltwater forcing. Proceedings of the National Academy of Sciences USA 110: 19,719-19,724.
According to Tedstone et al. (2013), "changes to the dynamics of the Greenland ice sheet can be forced by various mechanisms including surface-melt-induced ice acceleration and oceanic forcing of marine-terminating glaciers." And they note, in this regard, that "during summer, meltwater generated on the Greenland ice sheet surface accesses the ice sheet bed, lubricating basal motion and resulting in periods of faster ice flow." However, they say that "the net impact of varying meltwater volumes upon seasonal and annual ice flow, and thus sea level rise, remains unclear."

In an effort to bring some clarity to this situation, Tedstone et al. used "observations of ice motion to examine the surface melt-induced dynamic response of a land-terminating outlet glacier in southwest Greenland to the exceptional melting observed in 2012," when on 12 July of that year 98.6% of the Greenland ice sheet experienced melting (the most significant melt event since 1889), and when one week later 79.2% of the ice sheet melted and summer ice sheet runoff was ~3.9σ above the 1958-2011 mean, which mean value had been matched most recently in 2009.

The results of their analysis revealed that despite the record summer melting of 2012, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in the average year of 2009. In the final sentence of their paper's abstract, Tedstone et al. write their findings suggest "surface melt-induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios."

Archived 18 March 2014