In a previous post on the worrying pace of Greenland and Antarctic melting, I mentioned that Greenland’s melt rate had been the subject of a bit of discussion. There was evidence of rapid melting from Greenland’s southeast glaciers from the late 90s to the mid 2000s, but this “galloping” (as Kerr put it) pace seemed to have ended in 2005. Of course, the denialists jumped all over this apparent reprieve, using it to snipe at Al Gore and imply that further mention of accelerated Greenland melting was naught but greenie scaremongering.
As noted in the prior post, Pritchard et al. found that while this rapid acceleration did seem to peak around 2005 in the southeast, elsewhere in Greenland melt rates continued to accelerate. These findings, along with similar from Antarctica, have been given further support from GRACE (Gravity Recovery And Climate Experiment) satellite data, as published by Isabella Velicogna in a new GRL study: Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE.
GRACE data from Greenland and Antarctic ice mass balance from April 2002 through February 2009 confirm that not only has significant melting continued on both ice sheets, their respective rates are actually best fit by quadratic rather than linear trends- indicating that the melting of each is continuing to accelerate.
Those concerned about rapid ice sheet decay would do well to avoid the embarrassment of the denialists, and refrain from senselessly extrapolating such a short trend into the future- although there is certainly no harm in mocking how swiftly their talking points are continually refuted by reality. Likewise, those crowing about the minor “recovery” [still the third largest melt recorded] of Arctic sea ice should probably keep this paper in mind as well.
Snark aside, the results of the GRACE survey are troubling. Unfortunately- contra the denialists and to paraphrase Samuel Clemens- reports of the demise of accelerating melt have been greatly exaggerated. Velicogna finds that after applying a seasonal filter and a quadratic fit, the rate of Greenland ice loss doubled during the observed period while the rate in Antarctica increased by roughly 140%. This is not a matter of academic interest or rhetorical point scoring- such dynamic melting is precisely the kind of behavior that paleoclimatic data imply for the ice sheets, and why sea level rise will assuredly be much worse than what the base AR4 numbers reflect.