Tahiti yields ‘treasure trove’ of climate records

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An international team of scientists, supported by the Integrated Ocean Drilling Program, reunited at the University of Bremen to analyse a trove of coral fossil samples retrieved from Tahitian waters during October and November 2005.

Three weeks ago, led by chief scientists from France and Japan, the science party started their year-long analysis of 632 meters of fossil material retrieved from 37 boreholes drilled beneath the seafloor.

The initial conclusion is that the IODP Tahiti Sea Level Expedition has assembled the most accurate physical evidence available today of changes in sea level during the last deglaciation, including a full record of temperature and salinity changes in the southern Pacific.

Co-chief scientist Gilbert Camoin, of CEREGE, a geoscience research centre in France, summarized the expedition’s success: “Tahiti has given us a treasure of records that archive sea level change over approximately the last 20,000 years.

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 explains that Tahiti was chosen for this expedition because of its unique geology and its location: a relatively stable, volcanic island, Tahiti is subsiding at a rate of just .025 mm per year, in the southern Pacific far away from the previously glaciated regions. “Tahiti presents a microcosm of what’s happening globally in paleoclimatology today,” he says.

Japanese co-chief scientist Yasufumi Iryu, of Tohoku University, praises the quality of the cores obtained. “The longest continuous coral core we collected is 3.5 meters long,” he confirms. “It represents 350 years of coral growth.” Providing a reliable climate record with no gaps, massive coral samples–just five percent of the samples obtained–are highly valued by scientific investigators as they reconstruct climate variability and piece together frequency and amplitude of climatic anomalies such as El Ni