Despite dramatic increases in ice melt across Greenland in recent years, the speed of ice movement in some areas has slowed down rather than accelerated, scientists have found.
The finding, observed on a sector of the ice sheet that terminates on land rather than in the ocean, could mean that parts of Greenland's ice sheet may be less vulnerable to climate change than was previously thought.
Until recently, scientists thought that the increased volumes of meltwater from Greenland's ice in response to climate warming would speed up the motion of all parts of the ice sheet by helping the ice slide more rapidly.
However, the latest study by an international research team, including scientists from the University of Sheffield found that in recent decades, ice movement in some areas that terminate on land has slowed down rather than accelerated.
The discovery suggests that further increases in ice melting, fuelled by climate change, may further slow movement of these sectors of the ice sheet.
The team used satellite data to track the shift of ice features such as crevasses in an 8,000 square kilometres area of Greenland over three decades.
Researchers found that despite a 50 per cent rise in meltwater from the ice surface in recent years, overall movement in the past 10 years was slower than in previous decades.
They found that this was caused by large amounts of meltwater produced in summer producing channels at the base of the ice sheet, which drain away water efficiently, slowing the glacier's movement the subsequent winter.
Scientists said more research is needed to understand the movement of other parts of the ice sheet, which terminate in the ocean and which have seen acceleration in recent decades.
"Our research underscores the complexity of the relation between climate change affecting Greenland and the response of its ice sheet to the ongoing warming," said Professor Edward Hanna, from the Department of Geography at the University of Sheffield.
"We need to understand these ice-climate interactions better in order to be able to make more reliable global sea-level predictions," Hanna said.
"It is clearly not always a simple case of more icemelt resulting in faster-flowing ice, as was originally thought by some to be the case.
"On the other hand, there can be little doubt of the increasing contribution of mass loss from the Greenland ice sheet to global-sea-level rise over the last couple of decades and we cannot be complacent about further changes," Hanna said.
The study, carried out in collaboration with the University of Edinburgh and Universite Savoie Mont-Blanc in France, was published in the journal Nature.
