Science 321, 111—113 (2008)

The movement of ice sheets increases markedly when meltwater gets involved, according to researchers from Utrecht University in the Netherlands.

Just days after increased meltwater is produced, ice velocity can increase by a factor of four, say Roderik van de Wal and his colleagues. They used 17 years' worth of data from Global Positioning System units drilled into the western edge of Greenland's ice sheet to determine both ice velocity and disappearance rates. Despite detecting larger than previously observed meltwater-induced bursts in velocity, the team found that, in the long term, ice velocities have actually decreased slightly.

They suggest that ice sheets continually adjust to the amount of meltwater, keeping overall velocities more or less constant.