Robo-sub surveys glacier

Autosub, a robot submarine developed by Southampton’s National Oceanography Centre, has successfully completed six mapping missions under the Pine Island Glacier in the Antarctic.

The robot submarine is being used to understand the changes occurring to the Antarctic glacier, which has been thinning and accelerating since the 1970s. It is thought that together with surrounding glaciers, Pine Island is contributing around 0.25mm a year to global sea-level rise.

Steve McPhail, who led the Autosub team during the 10-day survey, said: ‘Autosub is a completely autonomous robot; there are no connecting wires with the ship and no pilot. Autosub has to avoid collisions with the jagged ice overhead and the unknown seabed below, and return to a pre-defined rendezvous point, where we crane it back onboard the ship.

‘Adding to the problems are the sub-zero temperatures and the crushing pressures at 1,000m depth. All systems on the vehicle must work perfectly while under the ice or it would be lost. There is no hope of rescue 60km in, with 500m of ice overhead.’

A recent report of the Intergovernmental Panel on Climate Change (IPCC) claims that it is difficult to predict how ice sheets will contribute to sea-level rise as little is understood about the behaviour of ice sheets.

However, scientists at the centre are hoping to move a step closer to understanding these changes by using Autosub to investigate the underside of the ice and measure shifts in the salinity and temperature of the surrounding water.

Once the data has been collected, Autosub is able to create a three-dimensional map that identified any areas of warmth in the ocean waters. In total, the project covered a distance of around 500km.

Leading the project, Adrian Jenkins of British Antarctic Survey said: ‘There is still much work to be done on the processing of the data, but the picture we should get of the ocean beneath the glacier will be unprecedented in its extent and detail. It should help us answer critical questions about the role played by the ocean in driving the ongoing thinning of the glacier.’

In addition to the Autosub exploration, other work undertaken during the trip included the positioning of five moored instrument arrays to record the variability in ocean properties over the next two years, profiling of ‘warm’ and melt-laden seawater, sampling the perennial sea ice and swath-mapping deep troughs on the sea floor.