Huge groundwater system discovered beneath Antarctica

By Mark Waghorn via SWNS

A huge groundwater system has been discovered - beneath Antarctica.

Hundreds of interconnected lakes and rivers are cradled within the ice itself and an international team mapped the actively circulating network.

It has implications for how the frozen continent reacts or contributes to climate change.

Lead author Chloe Gustafson, a graduate student at Columbia University, New York, said: "People have hypothesised there could be deep groundwater in these sediments. But up to now, no one has done any detailed imaging.

"The amount of groundwater we found was so significant, it likely influences ice-stream processes. Now we have to find out more and figure out how to incorporate that into models."

The mysterious reservoirs could speed melting glaciers and release carbon, say the researchers.

They concentrated on the 60-mile-wide Whillans Ice Stream that feeds the massive Ross Ice Shelf, the world’s largest.

Within is a subglacial lake and a sedimentary basin stretching beneath. Drilling into the first foot or so has brought up liquid water and a thriving community of microbes.

But what lies further down was unknown - until a US Air Force ski plane dropped off the intrepid scientists.

They used geophysical instruments placed directly on the surface over six exhausting weeks of travel and digging in the snow.

A technique called magnetotelluric imaging measured the penetration into the earth of natural electromagnetic energy generated high in the planet's atmosphere.

It comes in different degrees from ice, sediments, fresh water, salty water and bedrock to create MRI-like maps of various elements.

The tools were placed in snow pits for a day or so at a time - then taken out and relocated them. Readings were collected from almost 50 locations.

Natural seismic waves gathered by another team were also re-analyzed to help distinguish bedrock, sediment and ice.

The expedition found the sediments extend below the base of the ice from a half kilometer to nearly two kilometers before hitting bedrock - depending on location.

They are loaded with liquid water all the way down. If all was extracted it would form a water column up to 820 meters high.

It would be at least 10 times more than in the shallow hydrologic systems within and at the base of the ice.

Salty water conducts energy better than fresh water. The groundwater becomes more saline with depth.

It makes sense as the sediments are believed to have been formed in a marine environment.

Ocean waters probably last reached what is now the area covered by the Whillans during a warm period some 5,000 to 7,000 years ago.

The sediments were saturated with salt water. When the ice readvanced, fresh meltwater produced by pressure from above and friction at the ice base was evidently forced into the upper sediments. It probably continues to filter down and mix in today.

Slow draining of fresh water in Antarctica could prevent build-up at the base - acting as a brake on the ice's forward motion.

Measurements by other scientists at the 'grounding line' where the landbound ice stream meets the floating ice shelf show the water is less salty than seawater.

It suggests fresh water is flowing through the sediments to the ocean, making room for more meltwater to enter, and keeping the system stable.

But if the ice surface were to thin - a distinct possibility due to global warming - the direction of flow could be reversed.

Overlying pressures 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 Whillans already moves ice seaward about a meter a day - very rapid for glacial ice.

Furthermore, if deep groundwater flows upward, it could carry up geothermal heat naturally generated in the bedrock.

This could further thaw the base of the ice and propel it forward. But if that will happen, and to what extent, is not clear.

Sediments further down are also likely to be inhabited by microbes. Groundwater moving upward would bring up the dissolved carbon used by these organisms.

Added Ms Gustafon: "The confirmation of the existence of deep groundwater dynamics has transformed our understanding of ice-stream behaviour, and will force modification of subglacial water models."

If the ice shelves were to pull back in a warming climate, ocean waters could re-invade the sediments, and the glaciers behind them could rush forward and raise sea levels worldwide.

The findings were published in the journal Science.