Tuesday, May 27, 2008

Acidified seawater showing up along coast ahead of schedule

Seattle Times science reporter

Climate models predicted it wouldn't happen until the end of the century.

So a team led by Seattle researchers was stunned to discover that vast swaths of acidified seawater already are showing up along the Pacific Coast as greenhouse-gas emissions upset the oceans' chemical balance.

In surveys from Vancouver Island to the tip of Baja California, reported Thursday in the online journal Science Express, the scientists found the first evidence that large amounts of corrosive water are reaching the continental shelf — the shallow sea margin where most marine creatures live.

Off Northern California, the acidified water was only four miles from shore.

"What we found ... was truly astonishing," said oceanographer Richard Feely, of the National Oceanic and Atmospheric Administration's (NOAA) Pacific Marine Environmental Laboratory in Seattle. "This means ocean acidification may be seriously impacting marine life on the continental shelf right now."

All along the coast, the scientists found regions where the water was acidic enough to dissolve the shells and skeletons of clams, corals and many of the tiny creatures at the base of the marine food chain. Acidified water also can kill fish eggs and a wide range of marine larvae.

"Entire marine ecosystems are likely to be affected," said co-author Debby Ianson, an oceanographer at Fisheries and Oceans Canada.

Though it hasn't received as much attention as global warming, ocean acidification is a flip side of the same phenomenon. The increase in atmospheric carbon dioxide from power plants, factories and cars that is raising temperatures worldwide also is to blame for the increasing acidity of the world's oceans.

Normally, seawater is slightly alkaline. When carbon dioxide from the atmosphere dissolves into the water, it forms carbonic acid — the weak acid that helps give soda pop its tang. The process also robs the water of carbonate, a key ingredient in the formation of calcium carbonate shells.

Since the Industrial Revolution, when humans began pumping massive amounts of carbon dioxide into the atmosphere, Feely estimates the oceans have absorbed 525 billion tons of the man-made greenhouse gas — about one-third of the total released during that period.

By keeping some of the carbon dioxide out of the atmosphere, the oceans have blunted the temperature rise due to global warming. But they've suffered for that service, with a more than 30-percent increase in acidity.

More at the Seattle Times

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