Acidic Oceans

Greenhouse emissions’ warming effect on the atmosphere is bad enough, but their bigger threat is the ecological chaos they are causing as the world’s oceans become more acidic, according to a marine scientist.

Oceans are absorbing the glut of atmospheric carbon dioxide – stemming from two centuries of rampant burning of fossil fuels – at the rate of 1 million metric tons an hour.

Reacting with seawater, the absorbed carbon dioxide forms carbonic acid and throws marine chemistry out of whack. Without a major effort to curb emissions, a massive die-off will occur in coral reefs, the shells of crucial mollusk species will dissolve and key marine plant life, which produces half the world’s atmospheric oxygen, will disappear, said Marcia McNutt, a geophysicist who heads California’s Monterey Bay Aquarium Research Institute.


“The decisions you make, even though you live 1,000 miles from the nearest ocean, impact the oceans, which cover 71 percent of the Earth’s surface,” McNutt said.

Climate change has a far greater impact on the oceans than the atmosphere because oceans have absorbed 30 times more anthropogenic heat than have the skies, disrupting circulation patterns and the oceans’ ability to moderate the weather, she said. Thermal expansion accounts for a far greater portion of rising sea levels than melting ice.

McNutt’s research institute is often referred to as “the NASA of oceanography” because of the robotic exploratory equipment it uses to snoop around the ocean off the central California coast.

“The Monterey Bay is the best-observed piece of seafloor in the world,” she said. One of the disturbing trends the institute has detected is the disappearance of Pacific whiting, or hake, once the most important commercial finfish in the area.

“As the hake numbers started to plummet, there was a perfect correlation in the increase in jumbo squid. He grows to my size in one year … by eating everything in sight, including hake,” she said.

Oceanic warming off California not only invited in the squid, but drove away its predators, such as the orca. But more disturbing to McNutt is the decline in diatoms, a keystone unicellular plant species that had been dominant in the ocean.

“Suddenly in 2003, dinoflagellate took over,” McNutt said, referring to a competing species of plankton that has a much weaker ability to consume carbon dioxide. “The last time these guys were dominant was 55 million years ago for a period of 225,000 years, a time of massive extinctions.”

McNutt said the ocean itself can be part of the solution to climate change because its tides and winds are potential clean-energy sources. And seeding the ocean with iron could help spur growth of beneficial plant life that would pull carbon from the water and return oxygen to the air.

Brian Maffly, Salt Lake Tribune, 12 February 2008. Article.


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Ocean acidification in the IPCC AR5 WG II

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