Vijay Garg*
A team of scientists has mapped a huge, actively circulating ground-water system in deep sediments in West Antarctica. The team at Columbia University estimated that if all of it were extracted, it would form a water column from 220 to 820 metres high -- at least 10 times more than in the shallow hydrologic systems within and at the base of the ice -- maybe much more even than that. However, they noted that said such systems, prob-ably common in Antarctica, may have as-yet unknown implications for how the frozen continent reacts to, or possibly even contributes to, climate change.“People have hypothesised that there could be deep groundwa-ter in these sediments, but up to now, no one has done any detailed imaging,” said lead author Chloe Gustafson, who did the research as a graduate student at Columbia University’s Lamont-Doherty Earth Observatory. Scientists have, for decades, flown radars and other instruments over the Antarctic ice sheet to image subsurface features. Among many other things, these missions have revealed sedimen-tary basins sandwiched between ice and bedrock.
But airborne geophysics can generally reveal only the rough outlines of such features, not water content or other characteristics. In the re-search appearing in the journal Science, the team concentrated on the 60-mile-wide Whillans Ice Stream, one of a half-dozen fast-moving streams feeding the Ross Ice Shelf, the world’s largest.
To better map the sediments and their properties, they used geophysical instruments placed directly on the surface.Their analysis showed that, de-pending on location, the sediments extend below the base of the ice from a half kilometre to nearly two kilometres before hitting bedrock. And they confirmed that the sedi-ments are loaded with liquid water all the way down. They were also able to show that the groundwater becomes more saline with depth.However, the researchers said, if the ice surface were to thin -- a distinct possibility as climate warms -- the direction of water flow could be reversed. Overlying pres-sures would decrease, and deeper groundwater could begin welling up toward the ice base. This could further lubricate the base of the ice and increase its forward motion.—The Hawk Features
*Retired Principal, Malout, Punjab