Direct Observations of Basin-wide Acidification of the North Pacific Ocean

• Main Authors: Byrne, Robert H., Mecking, Sabine, Feely, Richard A., Liu, Xuewu
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Digital Commons @ University of South Florida 2010
• Subjects: seawater pH; ocean acidification rates; pH variability; Life Sciences; Pacific; Ocean acidification
• Online Access: https://digitalcommons.usf.edu/msc_facpub/1590; https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=2642&context=msc_facpub

Global ocean acidification is a prominent, inexorable change associated with rising levels of atmospheric CO2. Here we present the first basin-wide direct observations of recently declining pH, along with estimates of anthropogenic and non-anthropogenic contributions to that signal. Along 152°W in the North Pacific Ocean (22–56°N), pH changes between 1991 and 2006 were essentially zero below about 800 m depth. However, in the upper 500 m, significant pH changes, as large as −0.06, were observed. Anthropogenic and non-anthropogenic contributions over the upper 800 m are estimated to be of similar magnitude. In the surface mixed layer (depths to ∼100 m), the extent of pH change is consistent with that expected under conditions of seawater/atmosphere equilibration, with an average rate of change of −0.0017/yr. Future mixed layer changes can be expected to closely mirror changes in atmospheric CO2, with surface seawater pH continuing to fall as atmospheric CO2 rises.