Tuesday, 17 January 2012

Drilling for Lake Ellsworth.

Lake Ellsworth is a sub-glacial lake in West Antarctica, it is about 70 km west of the Ellsworth Mountains, and approximately 3.4 km beneath the West Antarctic Ice Shelf. The lake has a long narrow throat and is thought to be about 150 m deep, and to cover an area of about 29 km³, about the same size as Lake Windermere. It is one of about 400 subglacial lakes in Antarctica, insulated from outside world by the overlying glaciers, and kept above freezing by heat from the Earth's interior, these lakes often flow for long distances, none lake emptying into another. They are of extreme interest to scientists since they have been cut off from the outside world since the overlying glaciers formed, in West Antarctica about 150 000 years ago, and any life there will have been evolving in isolation for all that time, in extremely strange and harsh conditions; cold, dark and low in nutrients. The sediments bellow the lake will also tell us a lot about the climate at the time the lakes formed.

The location of Lake Ellsworth.

Lake Ellsworth is the subject of a British mission to drill through the ice and recover water and sediment samples from beneath the ice. A team of engineers has just returned to the UK having towed 7o tonnes of drilling equipment 250 km though the Ellesworth Mountains to the drilling site, in temperatures as low as -35 °C. The equipment is now 1.7 km from the Lake, at a sheltered site where it will be protected during the harsh Antarctic winter. Engineers and scientists will return to the site in December 2012, when the equipment will be moved into its final position and drilling will commence.

The drill will use hot water to bore a 360 mm borehole slowly through the ice. Once the drill is turned off the hole should reseal in about 24 hours. The borehole will be kept sterile using a powerful ultraviolet filtering system. Once the borehole is complete a probe will be used to collect water from the lake, and a sediment corer to collect sediment from beneath it.

The location of Lake Ellsworth beneath the ice, and how the drill will reach it. Not to scale.

A Russian team has been drilling towards Lake Vostok, on the East Antarctic Ice Sheet, and thought to be Antarctica's largest lake, for some years. They were within 29 m of the lake in February 2011, when they were forced to stop drilling due to the onset of the Antarctic winter, with drilling resuming in December 2011; they hope to break through to the lake early in 2012. In the winter of 2012-13 the Russian team hope to launch a robotic probe into the lake. An American project, the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD), hopes to start drilling towards Lake Whillans beneath the West Antarctic Ice Sheet in 2013. They also hope to launch a remote rover vehicle into the sub-glacial lake. Many scientists view these missions as good practice for any future mission to the sub-glacial ocean thought to exist on Jupiter's moon Europa.

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