Decadal Variation of the Surface Water P CO 2 in the Western and Central Equatorial Pacific

Abstract

The equatorial Pacific Ocean is one of the most important yet highly variable oceanic source areas for atmospheric carbon dioxide (CO ₂ ). Here, we used the partial pressure of CO ₂ ( P CO ₂ ), measured in surface waters from 1979 through early 2001, to examine the effect on the equatorial Pacific CO ₂ chemistry of the Pacific Decadal Oscillation phase shift, which occurred around 1988 to 1992. During the decade before the shift, the surface water P CO ₂ (corrected for temperature changes and atmospheric CO ₂ uptake) in the central and western equatorial Pacific decreased at a mean rate of about –20 μatm per decade, whereas after the shift, it increased at about +15 μatm per decade. These changes altered the CO ₂ sink and source flux of the equatorial Pacific significantly.