Researchers observed Greenland's "subglacial plumbing system" and how it evolves to slow down the ice sheet's movement towards the sea.
These new findings could help researchers predict how Greenland will respond to climate change, the University of Texas at Austin reported.
"Everyone wants to know what's happening under Greenland as it experiences more and more melt," said study coauthor Ginny Catania, a research scientist at the institute and an associate professor in the university's Jackson School of Geosciences. "This subglacial plumbing may or may not be critical for sea level rise in the next 100 years, but we don't really know until we fully understand it."
The researchers described a complex drainage system in which meltwater from the surface drains into naturally formed pipes, called moulins,that drain water to passageways between bedrock and the underlying ice. The higher the water level the faster the ice sheet moves.
The study results suggest meltwater does speed up the sliding of the ice sheet, but the ice becomes less sensitive to the process as the summer wares on. This suggests the "plumbing system" in adapting to the increase in meltwater linked to climate change.
To make their findings the researchers drilled 13 boreholes through ice up to 2,300 feet thick and measured the water pressure in these regions. The team found there are two key parts to sublglacial plumbing systems. The first drainage system flows through subglacial channels and regulates daily changes in ice flow while the second is separate from the channel network.
"At the beginning of the season, there's little exchange of water between these two systems, but they gradually connect over the course of the melt season, relieving pressure in the isolated regions of the bed," said Lauren Andrews, a Ph.D. candidate at The University of Texas at Austin.
This type of connection would lower water pressure and lead to a seasonal decrease in the ice sheet's sensitivity and would not move as much as surface ice melt suggests.
"If we don't get this hydrology right, and if we don't couple it to models of ice flow, then we can't model the system properly and won't be able to project into the future very well," Catania said.
The findings were published Oct. 2 in Nature.
