Ocean acidification varies with depth and time

Ocean acidification varies with depth and time, depends on ocean circulation and microbe activity as well as on ocean chemistry. So say researchers of Montana State University and the University of Hawaii who have studied 20 years of data taken as part of the Hawaii Ocean Time-series (HOT) Program at Station ALOHA, 115 km north of the island of Oahu.

“Our study reveals that on year-to-year timescales the rate of acidification varies considerably with climate-driven changes to ocean mixing and with the biological responses to nutrients brought up from the deep by such mixing,” John Dore of Montana State University told environmentalresearchweb. “This finding is important because it reveals physical and biological mechanisms by which the rate of acidification is altered in the natural system.”

Dore and colleagues found that there was a five-year period (from 1999 to 2003) where the surface ocean pH actually rose, indicating that the waters were becoming less acidic. They propose that phosphate fertilization caused by a period of anomalously deep mixing from 1997 to 1999 led to at least some of this reversal of acidification.

“Such events might provide clues as to how acidification could be potentially slowed through deliberate manipulation of ocean ecosystems through nutrient fertilization,” said Dore. “Although I’m not advocating such geo-engineering schemes at this time, I do think they warrant further feasibility studies. We need to understand the system better than we do.”

Liz Kalaugher, environmentalresearchweb.org, 12 August 2009. Full article.

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