Back to that ocean problem

Animals are already dissolving in Southern Ocean - environment - 25 November 2012 - New Scientist

It's been ages since I have posted anything about ocean acidification.   I still read about it, but a lot of the studies that have come out in the last year or so have been kind of dull and very technical.   I think there is a realisation that ocean biology, chemistry and ecology are more complicated than previously thought, making forecasts of the effects of ocean acidification a field with a lot of uncertainty.  

I have also been waiting for something more specific about some species that everyone thought would be first affected, and pteropods are high on that list.  So at last there is a study out about them, noting field research from a 2008 field trip.  (They take their time, don't they?).

From the link above:

In a small patch of the Southern Ocean, the shells of sea snails are dissolving. The finding is the first evidence that marine life is already suffering as a result of man-made ocean acidification.

"This is actually happening now," says Geraint Tarling of the British Antarctic Survey in Cambridge, UK. He and colleagues captured free-swimming sea snails called pteropods from the Southern Ocean in early 2008 and found under an electron microscope that the outer layers of their hard shells bore signs of unusual corrosion.

As well as warming the planet, the carbon dioxide we emit is changing the chemistry of the ocean. CO₂ dissolves in water to form carbonic acid, making the water less alkaline. The pH is currently dropping at about 0.1 per century, faster than any time in the last 300 million years....

It gets worse:

Aragonite is still relatively plentiful in most of the ocean, but Tarling suspected that some regions might already be affected by shortages.

He visited the Southern Ocean near South Georgia where deep water wells up to the surface. This water is naturally low in aragonite, meaning the surface waters it supplies are naturally somewhat low in the mineral – although not so much so that it would normally be a problem. Add in the effect of ocean acidification, however, and Tarling found that the mineral was dangerously sparse at the surface.

"It's of concern that they can see it today," says Toby Tyrrell of the National Oceanography Centre in Southampton, UK.

Aragonite-depleted regions are still rare, but they will become widespread by 2050, says Tarling. The polar oceans will change fastest, with the tropics following a few decades after. "These pockets will start to get larger and larger until they meet," he says.

Tyrrell says the Arctic will become undersaturated with respect to aragonite before the Antarctic. Patches of undersaturation have already been seen, for instance off the north coast of Canada in 2008.

The only way to stop ocean acidification is to reduce our CO₂ emissions, Tyrrell says. It has been suggested that we could add megatonnes of lime to the ocean to balance the extra acidity. However, Tyrrell says this is "probably not practical" because the amounts involved – and thus the costs – are enormous.