23 Jan 2012:
Ocean Acidity Rise Unprecedented
in Past 21,000 Years, Researchers Say
Carbon dioxide emissions caused by human activities over the last century have increased the acidity of the world’s oceans far beyond the range of natural variations
, which may significantly impair the ability of marine organisms such as corals and mollusks to form their skeletons or shells, a new study says.
Using computer modeling to simulate climate and ocean conditions from 21,000 years ago to the end of the 21st century, an international team of researchers calculated that current saturation levels of aragonite — a form of calcium carbonate and key indicator of ocean acidification — have already dropped five times below the pre-industrial range of natural variability in several critical coral reef regions. As the acidity of seawater increases, the saturation level of aragonite drops. If human combustion of fossil fuels continues at current rates, saturation levels can be expected to decrease further, possibly reducing calcification rates of some marine organisms by more than 40 percent within the next century, researchers say. “Our results suggest that severe reductions are likely to occur in coral reef diversity, structural complexity and resilience by the middle of this century,” said Axel Timmermann, a researcher at the University of Hawaii at Manoa and lead author of the study, published in the journal Nature Climate Change
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