Subglacial lakes may influence ice flow

From San Francisco, at a meeting of the American Association for the Advancement of Science

The flow of water into and out of massive, ice-covered lakes in Antarctica may influence the speed at which overlying glaciers move toward the sea, a new study suggests.

Some of the speediest glaciers in the West Antarctic Ice Sheet are hundreds of kilometers long, 50 km wide, and up to 2 km thick, says Robert Bindschadler, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Md. Many of the continent’s ice streams nourish ice shelves, which are country-size ledges of floating ice still attached to the land.

When Bindschadler and his colleagues scrutinized satellite observations of the Whillans and Mercer ice streams between 2003 and 2006, they noted significant changes in the altitude of 14 regions within those features. The researchers suggest that the areas cover subglacial lakes and attribute the altitude fluctuations to water flowing among those bodies. Such shifts have been reported elsewhere in Antarctica (SN: 6/17/06, p. 382: Available to subscribers at Subglacial lakes may not be isolated ecosystems) but haven’t been noted below fast-moving ice streams.

One subglacial body of water, dubbed Lake Englehardt, is about 10 km wide and 30 km long. Between 2003 and 2006, the upper surface of the kilometer-thick ice over the lake dropped an average of about 9 meters. So, about 2 cubic kilometers of water drained from the lake during that period, says Bindschadler. In the same interval, the ice rose over a smaller, nearby subglacial lake, signifying that the lake gained about 1.2 km3 of water.

The movements of water beneath ice streams may lubricate the flow of ice, says Bindschadler. “Water is critical because, essentially, it’s the grease on the wheel, but we don’t know the details yet,” he notes.

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