Although its almost impossible to be sure about the causes driving this, the authors of one study (and most of the press coverage) suggested that it was caused by warmer ocean waters, in turn caused by changing weather patterns, in turn caused by good ole global warming. One study argued that the melting of these particular glaciers had reached the point of no return, prompting one magazine to go as far as calling it a "holy shit moment in climate science".
In a neat demonstration of how you should never jump to conclusions no matter how 'obvious' they may be, two new studies have now shown that the real reason for the melting may well be increased geothermal heat flow caused by volcanism, and nothing to do with pumping out CO2 in the northern hemisphere. One study produced a heat map for the area which looks a lot like a stove top of hot spots, and another even discovered an active volcano beneath the ice not far away.
Global warming may indeed be playing a part in increasing melting in the Antarctic, but an active volcano beneath the ice sheet is probably a much more direct, if mundane, factor.