Over The Horizon

Corer Lost at Sea

The snap of a rope has severely set back a major Antarctic research project and devastated the scientists who had invested years of planning, effort and ingenuity in it.

Scientists from Victoria University had just begun to lower a 1.5 tonne "vibracorer" through a hole in the ice to sample the sea floor off the Victoria Land coast north of Scott Base, when the rope broke and the corer sank 330 metres to the bottom. The corer was being used to recover sea-floor samples to date the retreat of the Antarctic ice sheet in this area. Designed and built at the university, the machine was believed to be ahead of anything of its type in the world. The corer had been successfully tested and used in other research in Wellington Harbour. [Icy Cores, Dec 1992]

"We still can't understand how it happened, though we guess it is some unknown factor in the Antarctic environment," Dr Peter Barrett, director of the university's Antarctic Research Centre, says. "The rope was supposed to have a breaking strain of seven tonnes, and the corer weighs less than a tonne and a half."

Deteriorating ice conditions make recovery difficult now, and plans are being made for a recovery attempt next spring. Even if the corer is brought back, though, it is most likely to be unusable because of impact damage and corrosion. Nevertheless, plans for a new corer are already being made.

"It will take another two or three years to design and build," Dr Barrett says, "but the experience necessary for the task has not been lost, and interest in this sort of research is likely to increase. Before a new corer is tried out, though, we must find out what caused the rope to fail."

The Wellington Harbour study is looking at silting and pollution rates, and the corer has already played a useful part in determining past siltation (3cm/year at Petone Wharf).

In the Antarctic, the aim was to core through the harbour floor mud to the top of the last debris deposited by ice-age glaciers dating the first mud would then establish the time when the ice cap retreated past the core site.