Rivers of fast-flowing water have been discovered in west Antarctica beneath a large mass of glacier ice in an extensive, linked system of rapidly filling and emptying lakes, according to a report earlier this month for the journal Science. The waterways could have major implications for the relationship between global warming and the melting rates of Antarctic ice shelves.
The report, authored by UCSD glaciologist Helen Amanda Fricker of the Scripps Institution of Oceanography, described sightings of previously unknown subglacial lakes beneath the Whillans and Mercer Ice Streams – two quick-moving channels of ice that feed into the Ross Ice Shelf, Antarctica’s largest floating platform of ice, which is approximately the size of France.
Although researchers anticipated the existence of subglacial water, they were surprised by the system’s large scale and speed of the water flow.
“”We thought those changes took place over years and decades, but we are seeing large changes over months,”” Fricker said. “”The detected motions are astonishing in magnitude, dynamic nature and spatial extend.””
The motions were detected from 2003 to 2006, in which Fricker and her colleagues used NASA’s Ice, Cloud and Land Elevation Satellite to identify elevation changes in the ice sheet’s surface as small as 1.5 centimeters. According to Fricker, the fluctuations, recorded by the satellite stationed 600 kilometers above the earth’s surface, were changing so rapidly that it could only be the movement of water filling and draining from subsurface lakes.
The Antarctic ice sheet is the largest single mass of ice on earth, covering an area of almost 5.38 million square miles – nearly twice the size of Australia – and containing 7.2 million cubic miles of ice. Because of its size, the land mass is often studied as part of the ongoing debate concerning the stability of ice sheets, as well as the risk of their collapse and contribution to rising sea levels as a result of global warming. Fricker’s discovery of the subglacial lakes provides crucial new information.
“”To predict how the ice sheets might respond to global warming, this new information is vital as it gives us a more complete picture of what is happening under the ice,”” Fricker said.
Approximately 90 percent of the world’s ice is located in the Antarctic ice sheet, and rising atmospheric temperatures threaten its ability to support ice streams, in turn allowing more ice to enter the oceans and raise sea levels worldwide.
Currently, the relationship between ice stream activity and the climate is not clearly understood, but Fricker’s discovery raises concerns that the subglacial lakes could help lubricate the ice, quickly carrying it to the ice sheet’s edge and exacerbating melting.
If all the Antarctic ice was to melt, scientists estimate it could lead to a 23-foot rise in sea level worldwide. According to a new study, released by World Bank earlier this month, even a one-meter rise would devastate coastal and low-lying areas around the world.
The three largest subglacial lakes detected by ICESat measure up to 193 square miles – approximately 38.6 square miles larger than the area of California. During the three-year study, one lake – Subglacial Lake Engelhardt – drained a volume of 0.480 cubic miles, while another – Subglacial Lake Conway – gained 0.288 cubic miles of water. Overall, Fricker and her colleagues recorded a net gain in subglacial water, but have declined to draw conclusions about how the figure would affect the stability of the ice sheet.
By continuing observations of the ice streams, Fricker said she hopes to find more active regions elsewhere in Antarctica, as well as learn more about their variation through time.
“”We still don’t know how the subglacial water system varies on longer timescales from decades to centuries,”” Fricker said. “”To do this we need to continue monitoring the ice streams with ICESat and future follow-up missions.””
