Greenhouse gas pollution has acidified the coastal waters of western North America more rapidly than scientists expected, says a study published today in Science.

In a survey of waters stretching from central Canada to northern Mexico, researchers led by the National Oceanic and Atmospheric Administration's Richard Feely found cold, unexpectedly low-pH water "upwelling onto large portions of the continental shelf." In some locations, the degree of acidification observed had not been expected to occur until 2050.

Ocean acidification is a side effect of excessive atmospheric carbon dioxide, lesser-known but no less troubling than climate change. When seawater absorbs CO2, the proportion of hydrogen ions rises [pdf] – a phenomenon remembered from high school chemistry class as the reddening of a litmus test.

The availability of carbonate ions falls correspondingly, the trends dovetailing to form bad news for marine organisms whose shells or skeletons require calcium carbonate. The shells become weaker and dissolve. Among the affected creatures are corals, crustaceans and shellfish – and if those populations collapse, entire marine ecosystems will follow.

In September of 2005, Feely was among the authors of a Nature article predicting that acidication would claim Antarctic Ocean waters by 2050, spreading into the subarctic Pacific by 2100. "Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously," they wrote [pdf].

In the latest study, they found unusually low-PH water off the continental shelf of western North America. This occurred primarily at depths between 40 and 120 meters, but in one region off the California coast it extended all the way to the surface. Such upwellings are a seasonal phenomenon, the researchers noted, but appear to be getting worse, with low-pH water claiming ever-larger ocean areas.

"Our results show for the first time that a large section of the North

American continental shelf is impacted by ocean acidification," they wrote.

The waters now rising to the ocean surface were last exposed to atmospheric CO2 in the mid-2oth century. What hill happen, one wonders, when water that sank to the deep sea during our own CO2-choked time comes back again?

"Water already in transit to upwelling centers is carrying increasing anthropogenic CO2 and more corrosive conditions to the coastal oceans of the future," write the authors. Ocean acidification "could affect some of the most fundamental biological and geochemical processes of the sea in the coming decades." If anything, the clinical language of science only makes their words more disturbing.

Evidence for Upwelling of Corrosive 'Acidified' Water onto the Continental Shelf [Science]

Image: A dissolving shell, courtesy of Nature.

See Also:

WiSci 2.0: Brandon Keim's Twitter and Del.icio.us feeds; Wired Science on Facebook.