Three-way race to reach lost Antarctic lakes

Antarctic researchers are set to make first contact with long-lost lakes deep beneath the continent's ice – closely followed by second and third contact. Three expeditions will attempt to enter the hidden lakes over the next two years, in search of unknown kinds of life that have evolved in isolation. The projects could also determine if or when the west Antarctic ice sheet will collapse – one of the worst-case scenarios in future climate change.

Over the next few months a team from the British Antarctic Survey, based in Cambridge, UK, and other institutions will set up drilling equipment on the ice above Lake Ellsworth. They will return late next year to drill into the lake.

Ellsworth is buried under 3 kilometres of ice, in what was once a fjord. The team will break in by firing a jet of hot water into the ice. "We can get through those 3000 metres of ice in about three days," says lead scientist Martin Siegert of the University of Edinburgh, UK. The hot-water drill should also minimise contamination of the lake, as the melted pristine ice from the bottom of the borehole is cleaned and then used in the jet.

The hole will stay open for only 24 hours. During that time the team will lower in a probe to retrieve samples of water and sediment. A second probe will drill into the sediment on the lake floor and retrieve a core. Afterwards the hole will naturally close up. "It will be as if we were never there," Siegert says.

"We're confident we'll find life in the sediments," says Martyn Tranter of the University of Bristol, UK, but life in the nutrient-poor water is less likely. Tranter says any living things will be bacteria, perhaps feeding on sulphides from ground-up rock in the sediments.

Three kilometres above Lake Ellsworth (Image: British Antarctic Survey)

Race to the finish

The Ellsworth team are not the first to seek life in an Antarctic lake. Last year a Russian expedition drilled to within 29 metres of the surface of Lake Vostok, which lies 3750 metres below the ice of east Antarctica. They were forced to stop when winter closed in, but will resume drilling in January.

When they break into the lake early next year, its water should rise up the hole and refreeze. They will return late next year to get samples from this fresh ice – a sampling technique that is designed to minimise the human contamination.

Antarctica's plumbing

The third project, WISSARD, will drill into west Antarctica's Lake Whillans. Unlike Vostok and Ellsworth, which have been isolated for tens of thousands of years, Lake Whillans is part of an extensive network of lakes and channelsrunning under the ice, and is much more active.

"We know it fills with water and discharges," says Ross Powell of Northern Illinois University in DeKalb. It is "part of the plumbing" that collects water from streams under the ice and releases it into the sea.

The WISSARD team will spend two Antarctic summers setting up and testing their equipment before drilling into Lake Whillans in 2013 and 2014 using the same hot-water method as the Ellsworth team. Powell plans to observe the lake filling and discharging, and monitor how that affects the ice sheet above. The team will also send down a robot to explore the lake.

Collapsing ice sheet

The Ellsworth and Whillans projects will both help to answer the critical questions about whether, or when, rising global temperatures will cause the west Antarctic ice sheet to collapse.

Glaciers in the ice sheet have been disappearing for years. If the sheet collapses, sea levels will rise at least 3 metres, and possibly as much as5 metres, swamping low-lying areas worldwide.

The sediment core from Lake Ellsworth should tell us when the ice sheet last collapsed, says Dominic Hodgson of the British Antarctic Survey. The sediment deposited while the ice sheet has been present will have been ground-up rock, but when it was absent, marine sediment will have been deposited instead. "That provides a marker," Hodgson says, which can then be matched to temperature records obtained from ice cores.

Hodgson suspects the last collapse was 110,000 to 120,000 years ago. At the time temperatures in Antarctica were 6 °C warmer than today, and seas were 6.6 metres higher.

Alternatively the last collapse may have occurred 400,000 years ago – the warmest period of the past 500,000 years. "That would indicate that the west Antarctic ice sheet is more resilient," Hodgson says.

"What we'd really like is a continual record going back 2.5 million years," Siegert says. "That would tell us it's really robust." Hodgson thinks this is unlikely, however, because Antarctic ice loss is the only explanation we have for the rise in sea levels 120,000 years ago.