By Liz Kalaugher
In the central Arctic the speed of sea ice drift shows both a seasonal cycle and a long-term trend. Now, Einar Olason of the Max Planck Institute for Meteorology in Hamburg reckons he’s discovered three regimes that govern drift, depending on the time of year.
As he detailed at DACA-13 in Davos, between June and November mean ice drift speed varies with ice concentration, with ice tending to move faster as its concentration decreases. From December to March drift speed is inversely linked to ice thickness. And in April and May, when both ice thickness and concentration are constant, it’s fracture formation that makes the difference by weakening the ice cover and causing it to move more speedily.
The long-term trend in sea ice drift speed apparent in August, September and October seems to be linked to sea ice concentration.
Rob DeConto of the University of Massachusetts, meanwhile, believes that adding marine ice cliff failure into Antarctic ice-sheet models could help account for the ten metres or so of sea-level rise in the Pliocene around 3 million years ago that the models can’t reproduce.