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The core of the debate

Global warming - While debate rages over whether global warming is man-made, a Cornish company is helping find the answer by taking coral cores in Tahiti. Mark Hansford reports.

Is it merely a matter of time before global warming destroys life on earth- Or can proof that it is indeed the result of human activity help us save the planet?

Cornish marine contractor Seacore's latest project - extracting cores from tropical coral reefs to find carbon data millions of years old - may achieve just that if it uncovers compelling evidence that today's rate of climate change is unlike any other in history. It may even be the evidence to persuade the likes of US president George Bush that global warming is very rapid and very man made.

Pressure to understand climate change is constantly increasing. Last month research carried out by the British Trust for Ornithology warned that warming temperatures, melting of polar ice and rising sea levels will lead to the extinction of many species of animals and birds.

'In geological terms global warming is happening quickly. If we can find evidence of a similar rate of increase in the past, then that argues against it being a man-made phenomenon, ' says Seacore exploration director Marcus Rampley.

Seacore is extracting the core for client the Integrated Ocean Drilling Program (see box) in a ú2.5M ($4.5M) contract to perform a marine site investigation of the seabed at three offshore locations around the coast of the French Polynesian island of Tahiti in the South Pacific Ocean. This follows coring operations in the Arctic and Antarctic circles, and in sub-equatorial Lake Malawi.

The detailed and challenging investigation requires Seacore to sink 19 boreholes and take core samples of seabed sediments and substrata at up to 105m penetration in water depths ranging from 30m to 310m.

The expedition aims to provide geological information that will allow climate scientists to reconstruct the sea-level rise that followed the last major glacial event 21,000 years ago, when half of North America and most of Northern Europe were covered by thick ice sheets and sea level was about 120m lower than today.

In addition, the expedition aims to reproduce associated changes in sea surface temperatures and to analyse the effects of climatic and sea-level changes on reef building (see box).

'It's like counting the rings on a tree, ' says Rampley. 'We are targeting information on sediment in relatively undisturbed areas. Looking at the paleoenvironment that fossils lived in you can work out the sea temperature at that time, and then radio carbon date the fossil to be sure of its age.'

On last year's expedition to the Arctic Ocean Seacore was working in water depths of 800m to 1,400m, and recovered cores up to 428m into the seabed from sites along the 1,800km long Lomonosov Ridge, which extends from Greenland towards Russia (NCE 8/15 April 2004).

Initial results from that venture have already excited the scientific community by appearing to indicate that the Arctic Ocean was frozen as early as 15M years ago, much earlier than previously thought.

Back to Tahiti, and Seacore has plenty to worry about technically. 'For a start we cannot use anchors because they would damage the coral, ' says Rampley.

'Then there is cooling and clearing the drill. Ordinarily we use drilling mud to cool the drill bit and clear the cuttings.

But the problem is this mud is biodegradable, and that process uses oxygen, which would take oxygen away from the coral and damage it. So we are using seawater only as coolant, but that means we stand a real chance of the drill jamming up. It may compromise the quality of the core, ' he says.

And then there is another, not insignificant challenge, given recent events. 'We are working within 10km of the island, which is well known as a surfers paradise, ' says Rampley.

'That means big waves. We are working in the calm season - we hope.' And then there is the issue of where they are. Tahiti is still a long way from home if anything breaks and spares are needed.

'Our crews really are multidisciplined and by and large selfsufficient, ' reassures Rampley.

'The guys are mostly local and their background is fishing and mining. This gives them common sense and experience in working in a harsh environment. We then give them five years of training.

They don't have preconceived ideas and in a dilemma are very self reliant.' Seacore will drill with its own heave-compensated R100 drill rig, built initially for the Lomonosov Ridge project, mounted on the multi service construction vessel DP Hunter.

DP Hunter left port at Tampa, Florida, on 6 September, passing through the Panama Canal on 14/15 September. The ship is now on station off the coast of Tahiti and began coring last week. Rampley expects the work to take 40 days.

The recovered cores will be left complete and taken to the IODP Core Repository at Bremen University, Germany, for detailed analysis.

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