BioEd Online

Perched atop a thick ice shelf, scientists in Antarctica have begun drilling down into the frozen continent's deep history.

Engineers have drilled through the Ross Ice Shelf, through hundreds of metres of water underneath, and this past weekend poured concrete on the seafloor to anchor their next step. In the next couple of days, they plan to begin pulling up cores of sediment from the seabed.

Over the next 2 months, they hope to extract some 1,200 metres of core, recording about 7 million years of geologic and climatic history.

The US$30 million programme, called ANDRILL, is scientists' first attempt to drill deep cores beneath one of Antarctica's ice shelves, the floating plates of ice that extend from the continent's fringes. It is hoped that the cores will provide the first uninterrupted record of changes occurring beneath the Ross shelf. Such information is considered key to understanding how Antarctica's ice waxes and wanes as the climate changes.

"We want to know not just when the ice shelf formed, but its history through time," says Ross Powell of Northern Illinois University in DeKalb, one of the project's leaders. "If we can understand how the ice behaved in the past, then we can get a better understanding of what it may do in the future."

Earlier efforts have taken cores of Antarctic ice, and studied the gases trapped within to reveal climate changes stretching back 750,000 years. But the new sediment cores could provide a much longer and more detailed record.

"Scientifically, this is a really special opportunity," says the project's other leader, Tim Naish of the Institute of Geological and Nuclear Sciences in Lower Hutt, New Zealand.

On thick ice

The United States, New Zealand, Italy and Germany have joined forces in the programme. Many of its scientists and engineers are veterans of previous Antarctic drilling projects, such as the 3-year Cape Roberts Project in the late 1990s, which drilled through the much thinner sea ice.

In 1997, the first year of that project was halted when a storm broke up the sea ice, forcing the scientists to break camp and flee.

Next year, ANDRILL is scheduled to drill through a thin layer of sea ice. But this year, it is set up on the thicker and more stable ice shelf. Engineers have built a rig offshore, about 10 kilometres from New Zealand's Scott Base. The rig will run 24 hours a day, 7 days a week.

It hasn't been easy. Currents in the water beneath the ice have bent and flexed the drill pipe more than expected, slowing the drillers down. And getting through the ice shelf would have been impossible without a hot-water drilling system invented by New Zealand engineers. This is a ring that slides up and down the outside of the drill pipe, using hot water to keep the pipe from freezing to the ice.

The cores will be shuttled to the programme's 57 scientific staff at the US McMurdo base, just over a kilometre from the Scott base, to be photographed and split in half. One half will be taken apart for chemical and other analysis, the other is to be sent to Florida for storage in an Antarctic core facility.

Drilling is scheduled to run non-stop through to the end of December at which point exhausted scientists will pack up and head home, with much more work analysing the cores awaiting them.

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