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Over The Horizon

Icy Cores

Victoria University scientists and technicians have developed a machine that will sit on the Antarctic ocean floor up to a kilometre below the surface and dig into the sediment.

The vibra-corer, weighing 1.5 tonnes, is designed to fit through a 1.3-metre ice hole with its legs retracted. The legs fold out to support the body when it hits the sea bed hundreds of metres below the ice. Once there, the corer will sink a tube several metres into the sediment and bring the samples back to the surface.

Alex Pyne, of Victoria's Antarctic Research Centre, said he and his colleagues designed the corer because there was no machine available commercially that could do the job. Conventional corers rely on their weight to sink their tubes into the sea-floor mud, but the Antarctic mud is too stiff for such an approach to work. The vibra-corer uses batteries to vibrate the tube into the sea floor.

The group has been working on the design for the past three years, and recently tested the machine successfully from the Petone Wharf.

"We plan to carry out coring at ten sites, using a tractor crane and a hydraulic winch we designed ourselves, with a rope a thousand metres long," says Pyne. "Each coring operation should take about a day --  it takes quite a while to make a hole in the ice, which is about two metres thick."

The sediment studies aim to trace the retreat of the Antarctic ice margin over the last 20,000 years. At one time, the MacKay Glacier joined the Ross Sea ice shelf, but it has since retreated.

Once the sediment is analysed -- which could take 2-3 years -- scientists should have a reliable indication of the speed of retreat at the end of the last glaciation.

"Getting some hard data will be an important step forward in developing a model to show what might happen as the climate changes," notes Pyne.

The data can then be used to estimate the effect on the volume of Antarctic ice from past rises in global temperatures, and hence to what extent a future temperature rise could lead to further melting.

After its Antarctic sojourn, the vibra-corer is expected to be used in Wellington Harbour to monitor sedimentation and pollution.

The Antarctic Research Centre staff believe the device has a number of special applications with good commercial potential.