Three teams of scientists have taken a detailed look into the biogeochemistry, geophysics and geology of subglacial Lake Whillans, which lies 2,600 feet (800 m) beneath the Antarctic Ice Sheet.
An artist’s conception of the Antarctic subglacial environment. Image credit: Zina Deretsky / NSF.
The findings stem from NSF’s Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project.
In a paper published in the journal Geophysical Research Letters, Dr. Matthew Siegfried of the Scripps Institution of Oceanography and co-authors report that GPS data gathered over a period of five years indicate that periodic drainage of Lake Whillans can increase velocity at the base of the ice sheet and speed up movement of the ice by as much as 4% in episodic bursts, each of which can last for several months.
The scientists suggest that these short-term dynamics need to be better understood to help refine prediction of future, long-term ice sheet changes.
In a second paper, published in the journal Geology, Dr. Alexander Michaud of Montana State University and co-authors used data taken from a 15-inch (38-cm) long core of lake sediment to characterize the water chemistry in Lake Whillans and its sediments.
This team’s results indicate that lake water comes primarily from melting at the base of the ice sheet covering the lake, with a minor contribution from seawater, which was trapped in sediments beneath the ice sheet during the last interglacial period, when the Antarctic Ice Sheet had retreated. This ancient, isolated reservoir of ocean water continues to affect the biogeochemistry of this lake system.
This new finding contrasts with previous studies from neighboring ice streams, where water extracted from subglacial sediments did not appear to have a discernable marine signature.
In the third paper, published in the journal Earth and Planetary Science Letters, Dr. Timothy Hodson of Northern Illinois University and co-authors examined another sediment core taken from Lake Whillans to discover more about the relationship between the ice sheet, subglacial hydrology and underlying sediments.
Their findings show that even though floods pass through the lake from time to time, the flow is not powerful enough to erode extensive drainage channels, like the rivers that drain much of the Earth’s surface.
Rather, the environment beneath this portion of the ice sheet is somewhat similar to a wetland within a coastal plain, where bodies of water tend to be broad and shallow and where water flows gradually.
Together, these new publications highlight an environment where geology, hydrology, biology and glaciology all interact to create a dynamic subglacial system, which can have global impacts.
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Matthew R. Siegfried et al. Episodic ice velocity fluctuations triggered by a subglacial flood in West Antarctica. Geophysical Research Letters, published online March 16, 2016; doi: 10.1002/2016GL067758
Alexander B. Michaud et al. 2016. Solute sources and geochemical processes in Subglacial Lake Whillans, West Antarctica. Geology, vol. 44, no. 5, pp. 347-350; doi: 10.1130/G37639.1
T.O. Hodson et al. 2016. Physical processes in Subglacial Lake Whillans, West Antarctica: Inferences from sediment cores. Earth and Planetary Science Letters, vol. 444, pp. 56-63; doi: 10.1016/j.epsl.2016.03.036
