This peer reviewed new study in the journal Science puts yet another fork into the man-made global warming fear machine. See also July 2007 U.S. Senate Report: Latest Scientific Studies Refute Fears of Greenland Melt
I have a story coming tonight in print on a new paper tracking the impact over time of those iconic drainpipes for meltwater forming each summer on the warming flanks of the vast Greenland ice sheet. Here's the nub, with varied reactions coming from glaciologists later:
One of the most vivid symbols of global warming used by scientists and campaigners to spur society to curb climate-warming emissions is photography of gushing rivers of meltwater plunging from the surface of Greenland's ice sheet into the depths.
Recent studies have shown these natural drainpipes, called moulins, can speed up the slow seaward march of the grinding ice by lubricating the interface with bedrock below. The faster that ice flows, the faster seas rise. Now, though, a new Dutch study of 17 years of satellite measurements of ice movement in western Greenland concludes that the speedup of the ice is a transient summertime phenomenon, with the overall yearly movement of the grinding glaciers not changing, and actually dropping slightly in some places, when measured over longer time spans.
The work, the authors and other experts caution, does not mean that more widespread surface melting could not eventually destabilize vast areas of the world's second-largest ice storehouse. But for the moment, the study, which is being published in Friday's edition of the journal Science, throws into question the notion that abrupt ice losses in Greenland are nigh. "The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades," said the paper.
The study was led by Roderik S.W. van de Wal of the Institute for Marine and Atmospheric Research of the University of Utrecht.
Journal abstract follows:
Large and Rapid Melt-Induced Velocity Changes in the Ablation Zone of the Greenland Ice Sheet
By R. S. W. van de Wal et al.
Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years. The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades.
Science 4 July 2008: Vol. 321. no. 5885, pp. 111 - 113
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