The subglacial water system underlies West Antarctica's Thwaites Glacier, a Florida-sized outlet glacier in the Amundsen Sea considered a key factor in projections of possible rises in ocean levels, researchers at the University of Texas at Austin reported Tuesday.
On its own Thwaites contains enough fresh water to raise oceans by about three feet, they said.
The dynamics of the subglacial water system may be important in predicting the fate of the glacier, they said.
The swamp-like canal system lying under the deep interior of the ice sheet transitions to a series of mainly stream-like channels downstream as the glacier approaches the ocean, the researchers said.
The two configurations have contrasting effect on the movement of glacial ice, they said; swamp-like formations tend to lubricate the ice above them whereas streams, which conduct water more efficiently, are likely to cause the base of the ice to stick between the streams.
That causes the glacier's massive conveyor belt of ice to pile up at the zone where the subglacial water system transitions from swamps to streams, holding the massive glacier on the Antarctic continent.
"This is where ocean and ice sheet are at war, on that sticking point, and eventually one of them is going to win," geophysicist Don Blankenship said.
While Thwaites Glacier appears stable in the short term, holding its current position on the continent, the large pile of ice that has built up in the transition zone could rapidly collapse if undermined by ocean warming or changes to the water system, researchers said.
"We now understand both how the water system is organized and where that dynamic is playing itself out," Blankenship said. "Our challenge is to begin to understand the timing and processes that will be involved when that stability is breached."