Evidence for Upwelling of Corrosive "Acidified" Water onto the Continental Shelf
Richard A. Feely,1*
Christopher L. Sabine,1
J. Martin Hernandez-Ayon,2
Debby Ianson,3
Burke Hales4
The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of 
40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.
1 Pacific Marine Environmental Laboratory/National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, WA 98115–6349, USA.
2 Instituto de Investigaciones Oceanologicas, Universidad Autonoma de Baja California, Km. 103 Carr. Tijuana-Ensenada, Ensenada, Baja California, Mexico.
3 Fisheries and Oceans Canada, Institute of Ocean Science, Post Office Box 6000, Sidney, BC V8L 4B2, Canada.
4 College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Administration Building, Corvallis, OR 97331–5503, USA.
* To whom correspondence should be addressed. E-mail: richard.a.feely{at}noaa.gov
