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Tahiti Sea Level Expedition
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Tahiti Sea Level Expedition

July 14, 2010
The DP Hunter. The ship was the mission-specific platform chosen for Integrated Ocean Drilling Program (IODP) expedition 310, Tahiti Sea Level, in which scientists sampled fossil coral reefs to investigate the rise in global sea levels since the last ice age. The National Science Foundation is the lead agency of the IODP, which supported the expedition to Tahiti, while the expedition was conducted by the European Consortium on ocean Research Drilling (ECORD), a contributing member of IODP.

More about this Image The IODP Tahiti Sea Level Expedition amassed a huge amount of physical evidence showing changes in sea level during the last deglaciation, including a full record of temperature and salinity changes in the southern Pacific. The international team of researchers who comprised the expedition spent a year afterwards, analyzing 632 meters of fossil material retrieved from 37 boreholes drilled beneath the sea floor.

"Tahiti has given us a treasure of records that archive sea level change over approximately the last 20,000 years," said co-chief scientist Gilbert Camoin of the Centre Européen de Recherche et dEnseignement des Géosciences de lEnvironnement (CEREGE), a geoscience research center in France. "Because corals are ultra-sensitive to environmental change, we have been able--by splitting lengths of coral reef cores we acquired--to get better, more accurate descriptions of reef growth during the sea-level rise that occurred after the last glacial maximum, 23000 years ago."

Camoin said Tahiti was chosen for the expedition because of its unique geology and its location. A relatively stable, volcanic island, Tahiti is subsiding at a rate of just .025 millimeter per year in the southern Pacific, far away from the previously glaciated regions. Added Camoin, "Tahiti presents a microcosm of what's happening globally in paleoclimatology today."

Examining massive coral cores retrieved from 40 to 120 meters below sea level, the team identified grooved pairs of light and dark bands, with each pair measuring a centimeter in width and each representing one year of growth. Because coral fossils record age in their grooves, the researchers were able to determine a coral fossil's age within 30 years using radiometric methods.

"Coral reefs comprise the richest ecosystem on Earth," says Camoin. "And the most fragile." But he says that coral reefs, which play a prominent role in global matter cycles, are diminishing, with half of all reefs expected to disappear in the next few decades. [Research supported by NSF grant OCE 04-32224.] (Date of Image: November 2005)