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International ocean drilling pointing the way on climate change: scientist

English.news.cn   2011-11-15 13:44:19 FeedbackPrintRSS

WELLINGTON, Nov. 15 (Xinhua) -- The earth's oceans are rising as a result of rising levels of carbon dioxide in the atmosphere, but how fast and how high could they go?

Those questions will be discussed by about 40 scientists from around the world, who will gather in New Zealand this week to discuss the results of a global seabed drilling project that could help anticipate the effects of climate change on the oceans.

The scientists will be examining analyses of core samples of sediment dating back as far as 35 million years that were drilled in the Canterbury Basin off the east of New Zealand's South Island early last year, and comparing them with samples from other parts of the world.

"We're studying the past history of global sea level changes that will allow those who are anticipating the effects of global climate change to predict what might happen to the earth," said co- chief scientist on the expedition Craig Fulthorpe, of the University of Texas.

The expedition was part of the Integrated Ocean Drilling Program (IODP), which will compare core samples from the Canterbury Basin with those from Northern Hemisphere sites, to examine sea level changes on a global basis.

Funded by the United States, China, India, Europe, Australia, New Zealand and South Korea, the expedition set a record for drilling the deepest hole in the history of scientific ocean drilling, reaching down 1,927 meters off the coast of New Zealand.

The core samples have been studied and compared by the scientists from nine countries, who will review the results in the South Island town of Oamaru from Wednesday to Friday.

"It's given us a baseline to evaluate climate change for the next centuries," Fulthorpe told Xinhua in a phone interview Tuesday.

Other sediment samples were taken from off New Jersey on the U. S. east coast, the Bahamas and Tahiti, said Fulthorpe.

"To prove we're looking at a global process of sea level rises, we need to look at places as far apart as possible.

"Sea levels have been rising and falling throughout geological history. What we want to know is are they fast or slow? How do modern sea level changes fit in with the historical trends of sea level changes?"

The IODP chose the Canterbury Basin for drilling because of its distance from the other sites and because the large amount of sediment washed down from the South Island's Southern Alps contained a lot of detail about climate and sea level changes.

Researchers also wanted samples showing changes in ocean circulation that began when movements in earth's tectonic plates separated Antarctica from Australia, creating a new seaway about 34 million years ago.

Although the samples contained sediments dating back further, the global study was focusing on changes over the last 10 million to 12 million years when high concentrations of carbon dioxide in the earth's atmosphere caused large areas of ice to melt, particularly around the poles.

After the last Ice Age of 20,000 to 22,000 years ago, sea level rises had been "very high," said Fulthorpe.

The evidence from the samples showed up as "erosional non- conformities" in the sediment, such as high porosity, as well as concentrations of fossilized micro-organisms, which could be scientifically dated.

"These show us the timing of the cycles and the amplitude of the sea level changes," said Fulthorpe.

"There were several periods when carbon dioxide concentrations in the atmosphere were equal to or higher than those of today, so we have an idea of how the earth might respond to climate change."

Fulthorpe said the evidence strongly suggested "it's 90 percent probable" that the earth experienced cycles of global sea level rises and falls, but today's rising sea levels did not seem to fit the natural cycle as the high corresponding concentrations of carbon dioxide were not a natural phenomenon.

"The more that we learn about it, it seems unlikely that this is natural," he said.

The scientists meeting in New Zealand this week will come from Europe, Japan, the United States, Australia and New Zealand. Fulthorpe said a Chinese scientist had participated in the Canterbury Basin drilling expedition, but no Chinese scientists were attending the meeting.

The expedition was carried out on a former oil exploration drilling vessel that was converted into a floating laboratory and renamed the JOIDES Resolution. It was funded by the U.S. National Science Foundation, the European Consortium for Ocean Research Drilling, the Australian-New Zealand IODP Consortium, India's Ministry of Earth Sciences, China's Ministry of Science and Technology and the Korea Institute of Geoscience and Mineral Resources.

According to the IODP, 10 percent of the world's population lives within 10 meters of sea level. Current climate models predict a sea level rise of 50 centimeters to possibly more than a meter over the next 100 years, posing a threat to people in low- lying coastal communities around the world.

Editor: Zhang Xiang
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