Climate models predicted it wouldn’t happen until the end of the century.
So Seattle researchers were stunned to discover that vast swaths of acidified sea water are already showing up along the Pacific Coast as carbon dioxide from power plants, cars and factories mixes into the ocean.
In surveys from Vancouver Island to the tip of Baja California, 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. In some places, including Northern California, the acidified water was as little as four miles from shore.
“What we found … was truly astonishing,” said oceanographer Richard Feely, of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle. “This means ocean acidification may be seriously impacting marine life on the continental shelf right now.”
The phenomenon is an aspect of global warming scientists are just beginning to understand.
Acidified ocean water can be fatal to some fish eggs and larvae. It also interferes with the formation of shells and skeletons, harming corals, clams, oysters, mussels and the tiny plankton that are the basis of the marine food web.
“Their shells dissolve faster than they are able to rebuild them,” said Debby Ianson, an oceanographer at Fisheries and Oceans Canada and a co-author of the study published today in the online journal Science Express.
The acidified water does not pose a direct threat to people, said co-author Burke Hales, an oceanographer at Oregon State University. “We’re not talking battery acid here.”
Normally, sea water is slightly alkaline. When carbon dioxide dissolves into the water, it forms carbonic acid — the weak acid that helps give soda pop its tang. That lowers the water’s pH, or makes it slightly more acidic. 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, the oceans have absorbed 525 billion tons of the greenhouse gas, Feely estimates. That’s about a third of the man-made emissions during that time.
By reducing the amount of carbon dioxide in 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.
Until now, researchers believed most of the acidified water was confined to the deep oceans.
But during ship-based surveys last year, Feely and his colleagues found the natural upwelling that occurs along the West Coast each spring was pulling the acidified water up onto the continental shelf.
“This is another example where what’s happening in the natural world seems to be happening much faster than what our climate models predict,” said Carnegie Institution climate scientist Ken Caldeira, whose work suggested it would be nearly 100 years before acidified water was common along the West Coast.
And there’s worse to come, the scientists warn.
The acidified water upwelling along the coast today was last exposed to the atmosphere about 50 years ago, when carbon-dioxide levels were much lower than they are now. That means the water that will rise from the depths over the coming decades will have absorbed more carbon dioxide, and will be even more acidic.
“We’ve got 50 years’ worth of water that’s already left the station and is on our way to us,” study co-author Hales said. “Each one of those years is going to be a little bit more corrosive.”
Some creatures, like jellyfish, actually thrive in more acid waters. Adult mussels have a protective coating that may protect their shells.
But many other species are likely to suffer, including commercially important fish like pollock and salmon, which could see their food supply diminish.
“I think this is a red flag for us, because it’s right at our doorstep on the West Coast,” said Victoria Fabry, a biological oceanographer at California State University San Marcos who was not involved with the study. “It’s telling us that we really need more monitoring to figure out what’s going on.”
Sandi Doughton, Seattle Times, 22 May 2008. Article.
