Corrosive seawater burps up temporarily
Seawater with the potentially shell-disrupting chemistry
predicted for the open ocean after 2050 has already surfaced along
In spring 2007, the corrosive, deep water rose temporarily to
the Pacific surface some 40 kilometers roughly west of the California-Oregon
border, says Richard Feely of the National Oceanic and Atmospheric
Administration’s Pacific Marine Environmental Laboratory in
Deeper water normally swells upward at this time of year. But so much carbon dioxide — from natural and human-related processes — had dissolved in the water that the upwelling had a pH around 7.7. Surface water in the region typically has a pH of between 8.0 and 8.3 (a pH below 7 is acidic).
Gloomy estimates hadn’t predicted such a pH drop at the ocean surface until the second half of the century, Feely says. “This means that ocean acidification may be seriously impacting marine life on our continental shelf right now,” he says.
Feely blames human releases of greenhouse gas for creating the conditions that led to the upwelling. Deeper water naturally dips closer to acidity and carbonate scarcity, and human additions of carbon dioxide have expanded this zone upward.
“I was expecting that upwelling systems would be the first
place where corrosive waters would reach the surface, but I hadn't really
thought we were already there,” says Corinne Le Quéré of the
"What this study will really do is to point at where the biologists should come and study the impact of ocean acidification," says Le Quéré.
Just what the slosh of unusually low pH meant to the sea
creatures isn’t clear, says Victoria Fabry of
Feely and his colleagues discovered the extent of the upwelling
during a research cruise last May and June. The research team sampled water
along a series of paths sticking out from the shore like teeth on a somewhat
splayed comb. The cruise data can’t tell them how the water moved along the
coast in later days or months, but Feely says he’s seen signs that it rolled
Some colder water normally rises toward the sea surface
along the coast at this time of year, says coauthor Christopher Sabine, also of
With the industrial age, extra carbon dioxide wafts into the atmosphere and gets picked up by the sea. The oceans now take up 30 million metric tons of carbon dioxide a day, Sabine says. The extra dose makes the pH decline in the water column more dramatic so lower pH water is closer to the surface, where the upwelling originates.
“The water it’s grabbing is now corrosive, and it wasn’t before,” he says.
The California report looks like only the second report of low-carbonate,
or undersaturated, water on any sea surface, says Toby Tyrrell of the National
Oceanography Centre at the University of Southampton in England. He and his
colleagues reported the first, in the
Other regions with water dynamics similar to those off the
Hoegh-Guldberg O, et al. 2007. Coral reefs under rapid climate change and ocean acidification.
Science 318(Dec. 14):1737-1742.
Orr, J.C., et al. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature 437(Sept. 29)):681--686. doi:10.1038/nature04095
Feely, R.A., et al. In press. Evidence for upwelling of corrosive “acidified” water onto the continental shelf. Science 320(June 13):1490 - 1492. DOI: 10.1126/science.1155676
A map and slide show of predicted changes in ocean surface waters for this century (magenta outlines the emerging blue zones that are undersaturated in aragonite, a kind of calcium carbonate)