July 9, 2013
Swamp-Like Water System Revealed Under Antarctica’s Thwaites Glacier
Lee Rannals for redOrbit.com - Your Universe Online
While using an innovative radar analysis method to accurately image the sub-glacial water system under West Antarctica's Thwaites Galcier, scientists discovered a swamp-like canal system beneath the ice.
The scientists, from The University of Texas at Austin's Institute for Geophysics, reported in the Proceedings of the National Academy of Sciences (PNAS) that the swamp-like canal is several times as large as Florida's Everglades.
Thwaites contains enough fresh water to raise oceans by about three feet, and is a critical gateway to the majority of West Antarctica's potential sea level contribution of about 16 feet. The latest observations suggest that the dynamics of the sub-glacier water system may be as important as well-recognized ocean influences in predicting the fate of Thwaites Glacier.
The team used an innovation in airborne radar analysis developed by lead author Dusty Schroeder for the survey. This new method helped show that Thwaites' sub-glacial water system sits under the deep interior of the ice sheet, shifting to a series of mainly stream-like channels downstream as the glacier approaches the ocean.
Other ice-penetrating radar analyses have technical challenges related to the effects of ice temperature, making it difficult for scientists to confirm the extent and organization of these water systems. The new technique looks at the geometry of reflections to solve this problem.
"Looking from side angles, we found that distributed patches of water had a radar signature that was reliably distinct from stream-like channels," said Schroeder.
Being able to distinguish sub-glacial swamps from streams is important because they have contrasting effects on the movement of glacial ice. Swamp-like formations lubricate the ice above them, while streams cause the base of the ice to stick between the streams. This change in slipperiness causes the glacier's ice to pile up where the sub-glacial water system transitions from swamp to streams. This transition forms a stability point along a sub-glacial ridge that holds the massive glacier onto 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," said co-author Don Blankenship, a senior research scientist from the Institute for Geophysics.
The team's observations suggest that the glacier is stable in the short term, but a large pile of ice that has built up in the transition zone could rapidly collapse if undermined by the ocean warming or changes to the water system.
"Like many systems, the ice can be stabilized until some external factor causes it to jump its stability point," said Blankenship. "We now understand both how the water system is organized and where that dynamic is playing itself out. Our challenge is to begin to understand the timing and processes that will be involved when that stability is breached."