PhysOrg - New Computer Modeling Suggests US Pacific Coast Seawater Will Acidify Faster Than Expected
An upwelling zone is one in which waters from the deep ocean well up to replace water displaced by summer surface winds, which push water away from the coast. The upwelled deep water tends to contain high concentrations of dissolved carbon dioxide (CO2) from the respiration of microbes on the ocean floor, and this adds to the dissolved atmospheric CO2, which is rising, producing a region of marked decreases in pH.
When CO2 dissolves in seawater it reduces the pH by the production of carbonic acid and release of H+ ions, a process known as “acidification.” According to the International Panel on Climate Change (IPCC), the mean pH of open ocean surface water is 7.9-8.3, and even with reducing pH will still be slightly basic. Even very small changes in the pH can affect marine ecosystems, but the effects are poorly known. A reduction of 0.1 in pH corresponds to a 30% increase in H+ concentration.
A reduction in ocean surface pH reduces the amount of carbonate ions in seawater, and these are used by many shell-building creatures in building their shells. A reduction in the carbonate concentration also reduces the saturation state of the mineral aragonite, which is a form of calcium carbonate also commonly used in shell building.
The computer model was developed by a team of researchers at the Swiss Federal Institute of Technology (ETH) in Zurich and concentrated on the California Current System, the upwelling region off the western coast of the USA. The aim of the research team, led by ocean biogeochemist Professor Nicolas Gruber, was to examine the effects of linking rising atmospheric levels of CO2 and the CO2 already dissolved in the seawater.
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http://phys.org/news/2012-06-ocean-ph-falling-rapidly.html
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