Massive floods deep below Antarctica’s surface are accelerating the flow of glaciers into the ocean, a study has found, adding to the growing concern about the pace at which glaciers are melting into the seas.
The study, published online in the journal ‘Nature Geoscience’, found that a hidden network of glacial lakes far below the Antarctic surface regulates the motion of the continent’s ice rivers. When the subglacial lakes overflow, the ice above accelerates towards the ocean.
The study, published online in the journal ‘Nature Geoscience’, found that a hidden network of glacial lakes far below the Antarctic surface regulates the motion of the continent’s ice rivers. When the subglacial lakes overflow, the ice above accelerates towards the ocean.By tracking both the ocean-bound movement of East Antarctica’s Byrd glacier and the events in two lakes that lie beneath it, a team of scientists led by Leigh Stearns of the University of Maine showed that the glacier sped up between late 2005 and mid-2007 precisely when ice-penetrating radar imagery from satellites showed that both lakes were overflowing.
Conversely, the movement of the glacier slowed when the flood ceased and the lakes began to refill.
“Our findings provide direct evidence that an active lake drainage system can cause large and rapid changes in glacier dynamics,” the researchers concluded.
Now, for the first time, the US study has provided evidence that sub-surface floods can indeed act like a “turbo lubricant” for glaciers.
“It’s like putting in a squirt of oil,” Andy Smith of the British Antarctic Survey, was quoted as saying by New Scientist. “The water lubricates the base of the glacier,” he said.
The exact reason for flooding is not known, but researchers watching the movement of ice in satellite images have noticed that the ice appeared to “breathe” in some places, apparently linked to the ebb and flow of water underneath. Lead researcher Stearns said when the hollows overflow, a flood of water spreads beneath Byrd Glacier. “The extra water overwhelms the subglacial drainage system. It can’t escape fast enough, so spreads out beneath the glacier bed and reduces the friction between the ice and the rock, allowing the glacier to slide faster,” Stearns stressed.
Scientists believe that the pace of the movement of these huge bodies of ice into the ocean help determine the speed at which sea levels rise. Huge increases (measured in tens of centimetres and inches) could wreak disaster for millions of people living in low-lying areas around the world.
The UN Intergovernmental Panel on Climate Change (IPCC) warned last year that thermal expansion will push sea levels up 18 to 59 centimetres (7.2 to 23.2 inches) by 2100, enough to wipe out several small island nations and severely disrupt low-lying mega deltas in Asia and Africa.
Smith said that similar events have been seen in Greenland, but since the lakes there lie at the surface of the ice, the mechanism must be different. Temperatures in Greenland vary more than they do in Antarctica, where the summers are not warm enough to generate significant melt ponds at the surface.
“In Antarctica, it appears that the ice at the very bottom of the glacier melts slowly and accumulates in hollows in the rock,” said Smith.
He stressed the temperature at the bottom of the ice sheet stays very close to melting point — geothermal energy and friction warm it slightly and the kilometres of ice insulate the area keeping it at a relatively stable temperature.