A Surface pCO2 Increasing Hiatus in the Equatorial Pacific Ocean Since 2010

We used multiple data sets to investigate the decadal and longer time scale variability of sea surface partial pressure of CO2 (pCO(2)) over the equatorial Pacific Ocean from 1990 to 2019. Unlike the increasing trend in the global oceanic pCO(2), both the Nino 3.4 and warm pool regions featured distinct decadal variabilities. A pCO(2) increasing stagnation, a hiatus stage, was identified in the Nino 3.4 region from 2010 to 2019. Further analysis demonstrated that low-frequency pCO(2) was negatively correlated with the Interdecadal Pacific Oscillation (IPO) index. Both the 2009/10 and 2015/16 El Nino events and an increasing phase of IPO contributed to this long pCO(2) stagnation. Correspondingly, a weaker upwelling was induced in the central and eastern tropical Pacific as the trade winds weakened and thus stagnated the increase in pCO(2) in the Nino 3.4 region. Our results imply a significant impact of climate variabilities on sea surface pCO(2) in the equatorial Pacific.