Direct observations of basin-wide acidification of the North Pacific Ocean
Article first published online: 20 JAN 2010
Copyright 2010 by the American Geophysical Union.
Geophysical Research Letters
Volume 37, Issue 2, January 2010
How to Cite
2010), Direct observations of basin-wide acidification of the North Pacific Ocean, Geophys. Res. Lett., 37, L02601, doi:10.1029/2009GL040999., , , and (
- Issue published online: 20 JAN 2010
- Article first published online: 20 JAN 2010
- Manuscript Accepted: 25 NOV 2009
- Manuscript Revised: 20 NOV 2009
- Manuscript Received: 15 SEP 2009
- seawater pH;
- ocean acidification rates;
- pH variability
 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.