First author

Credit: H. PAELIKE

In August 2004, an international team of researchers extracted 400 metres of sediment core from the Arctic sea floor. It was a technical achievement that many thought impossible. The team is now using the sedimentary record to reveal past climate changes in the Arctic, which could elucidate future climate trends.

For example, the period known as the Palaeocene/Eocene thermal maximum interests climatologists because it is similar to today's warming climate. And the team has discovered that during this period, 55 million years ago, the sea surface temperature in the Arctic was as high as 25 °C.

The results have implications for our understanding of environmental change, says co-author Kathryn Moran, an oceanographer at the University of Rhode Island and one of the project's primary architects. Moran tells Nature about the expedition.

What technological advances made this expedition possible?

Sea ice moves constantly and can be up to three metres thick. So we worked with three icebreakers, one of which was fitted out to drill into the seafloor. The drill ship maintained a fixed location, and the other two vessels protected it by breaking up ice and pushing the pieces away. This stopped the drill ship being knocked out of position.

What did you miss most while on site?

We lacked very little because the Swedish Polar Research Secretariat, which organized the fleet, took care of our every need. They provided saunas, excellent food and a bar. They even threw us a party with surströmming — fermented Baltic herring. We had another party when we reached the North Pole: while guards with shotguns stood watch for polar bears, we walked on to the ice and celebrated.

What is your dream tool; what would make expeditions easier?

A seafloor-drilling system that stayed in place no matter what the conditions were. Money's the biggest hurdle right now. Drilling is an art, and mechanically complicated. There is one such drill in development, but it's in the very early stages of planning.

What can you say about global warming today based on your findings?

The Arctic is currently warming, but we have evidence that it used to be much warmer. We hope that our results can be used by climate modellers as ‘ground truth’ so that they can refine their predictions.