By John Henzell
    Stuff

    Wednesday 29 November 2006

    A New Zealand-led drilling team in Antarctica has recovered three million years of climate history, but the news is not good for the future.

    Initial analysis of seafloor cores near Scott Base suggest the Ross Ice Shelf had collapsed in the past and had probably done so suddenly.

    The team's co-chief scientist, Tim Naish, said the sediment record was important because it provided crucial evidence about how the Ross Ice Shelf would react to climate change, with potential to dramatically increase sea levels.

    "If the past is any indication of the future, then the ice shelf will collapse," he said.

    "If the ice shelf goes, then what about the West Antarctic Ice Sheet? What we've learnt from the Antarctic Peninsula is when once buttressing ice sheets go, the glaciers feeding them move faster and that's the thing that isn't so cheery."

    Antarctica stores 90 per cent of the world's water, with the the West Antarctic Ice Sheet holding an estimated 30 million cubic kilometres.

    In January, British Antarctic Survey researchers predicted that its collapse would make sea levels rise by at least 5m, with other estimates predicting a rise of up to 17m.

    Naish, a sedimentologist with the Institute of Geological and Nuclear Sciences, said the drilling team had banked on recovering about 30m of sediment core a day but was far exceeding that.

    In one day this week the team, organised by Antarctica New Zealand, retrieved 83m, containing climate records spanning about 500,000 years.

    "We're really getting everything we've dreamed of. What we're getting is a pretty detailed history of the ice shelf," he said.

    "You go from full glacial conditions to open ocean conditions very abruptly. It doesn't surprise us that much that the transition was dramatic.

    "We know from the Larsen Ice Shelf (which collapsed on the Antarctic Peninsula in 2002) that they go extremely quickly." The cores had to be sent from Antarctica to get a definitive date, but the indications were the team had reached sediments laid down about three million years ago.

    "Once the date is more precise we'll be able to look at what the ice shelf was doing during periods when we know from other evidence that it was 2deg to 4deg warmer than today," Naish said.

    The team's project manager, Jim Cowie, said the unexpectedly rapid progress of drilling came after decades of experience in Antarctica.

    This included a preliminary sediment recovery project run by Antarctica New Zealand at Cape Roberts and involved researchers from seven countries.