Though more than 150 Antarctic subglacial lakes have been discovered, it is thought thousands may exist, as much of the bed of Antarctica remains un-surveyed. Now it appears that rivers the size of the Thames, flowing beneath the ice of Antarctica, function as a drainage system.

According to a British team led by University College London (UCL) scientists at the Natural Environment Research Council (NERC) Centre for Polar Observation and Modelling (CPOM), Antarctica’s buried lakes are connected by a network of rivers moving water far beneath the surface.

In a letter to the journal Nature, they report that rivers the size of the Thames have been discovered and are moving water hundreds of miles under the ice.

The leader of the team, Professor Duncan Wingham, of UCL, director of CPOM, says:

Previously, it was thought water moves underneath the ice by very slow seepage. But this new data shows that, every so often, the lakes beneath the ice pop off like champagne corks, releasing floods that travel very long distances.

Why is this significant? Let’s backtrack. The subglacial lakes of Antarctica are regarded as “time capsules” of the period when the continent began to freeze over. Years ago, researchers found unexpected evidence of a great lake of liquid water in the bedrock deep below 30 million years’ of ice at the Russian Vostok research station, the most isolated manned research outpost on Earth. Lake Vostok is the largest of more than 70 subglacial lakes in Antarctica. Since subglacial lakes in Antarctica were first identified in the 1960s, more than 150 have been discovered; though it is thought thousands may exist, as much of the bed of Antarctica remains un-surveyed.

Then NASA proposed that if there really was life elsewhere on the solar system, then maybe it was hanging on in the liquid ocean deep under the ice of Jupiter’s moon Europa. Scientists believe any life the subglacial lakes contain might shed light on extreme environments on other worlds.

So for the following years, Russian, British and U.S. scientists wondered how they could break the seal and penetrate the hidden world of Lake Vostok without introducing contamination. Below, sealed beneath ice in some cases miles thick, life could be pursuing a separate evolution in scores of subglacial polar lakes.

Which brings us to last month’s announcement from the UCL scientists.

The rivers’ flow presents a drainage system, of sorts, and the presence of the drainage system challenges the widely held assumption that the Antarctic lakes evolved in isolated conditions for several millions years and thus may support microbial life that has evolved “independently.” As aforementioned, it has been suggested that if microbes exist in the lakes, they could function in the same way as those in the subsurface ocean of Jupiter’s moon Europa or within subsurface water pockets on Mars.

Plans to drill deep beneath the frozen wastes of the Antarctic, to investigate subglacial lakes where ancient life is thought to exist, may have to be reviewed following the team’s discovery. Several groups, under the umbrella of the Scientific Committee on Antarctic Research (SCAR), are currently investigating the prospect of drilling down to subglacial Antarctic lakes. The most advanced UK plans are to explore Lake Ellsworth.

“What this paper shows is that not only could you contaminate a lake, you could contaminate the whole drainage system,” Wingham told BBC News.

The recent discovery, which came as a great surprise to the team, also raises the possibility that large flood waters from deep within the interior may have reached the ocean in the past — and may do so again. The scientists believe that every so often there are large flows of water from one lake to another along rivers the size of the Thames. Most of the time there is very little discharge, but if a lake over pressurizes, a flood occurs that forces the water along the river to the next lake.

According to the team’s announcement, “Ultra-precise measurements were taken using radars on the European Space Agency ERS-2 satellite to examine in detail small changes in the surface of some of the oldest, thickest ice in Antarctica. The satellite found synchronous changes in the surface height separated by 290 kilometres [sic.].”

The scientists argue that the only possible explanation of these changes is that a large flow of water must have occurred beneath the ice from one subglacial lake into several others. The finding re-invigorates old speculations that Lake Vostok, which contains 5,400 cubic kilometers of water — “equivalent to London’s water consumption over 5,000 years — may have generated huge floods that could reach the coast.

The latest research raises the prospect that the same thing could happen again, though any discharge would probably take place over a period of months and would change sea level by less than a centimeter.

Resources

Discovery of Antarctic subglacial rivers may challenge excavation plans
press release
University College London, April 21, 2006

Rapid discharge connects Antarctic subglacial lakes
Authors: Duncan J. Wingham, Martin J. Siegert, Andrew P. Shepherd and Alan S. Muir
Nature, April 20, 2006

Secret rivers found in Antarctic
by Helen Briggs
BBC News, April 19, 2006