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Researchers investigate increased ocean acidification

Credit: Tiago Fioreze / Wikipedia

by Christopher Packham, Phys.org, Aug 3, 2015 – The primary cause of global ocean acidification is the oceanic absorption of CO2 from the atmosphere. Although this absorption helps to mitigate some of the effects of anthropogenic climate change, it has resulted in a reduction of oceanic pH levels, with its own set of environmental consequences. Coral bleaching, algae loss, and decreasing oceanic oxygen levels are all attributable to the reduced pH of the oceans. Additionally, acidification poses a threat to human industry with projected declines in commercial fisheries, the breakdown of food webs, and a decline in tourism as ocean ecosystems and the natural environment suffer degradation. The current pace of acidification is greater and faster than at any time in the last 300 million years, and bears close scrutiny.

Because of the lack of data about basin-wide pH changes at varying depths, an international group of investigators conducted a study of decadal acidification in Atlantic Ocean water masses, and compared the results to existing climate models. They’ve published their conclusions in the Proceedings of the National Academy of Sciences.

Earth climate models project that in the last decade alone, ocean acidity has exceeded cyclic changes in historical analogs. The current study tracked pH levels across two decades and data collected from three cruises in 1993, 1994, and 2013. The observations correspond closely with the model predictions of pH changes in the near surface and upper waters. “For the first time, to our knowledge,” the authors write, “our observations confirm the major role of mode and intermediate waters at the basin scale in the acidification of the ocean interior, which was also evidenced in the climate models.”