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 (pCO2) over the equatorial Pacific Ocean from 1990 to 2019. Unlike the increasing trend in the global oceanic pCO2, both the Niño 3.4 and warm pool regions featured distinct decadal variabilities. A pCO2 increasing stagnation, a hiatus stage, was identified in the Niño 3.4 region from 2010 to 2019. Further analysis demonstrated that low-frequency pCO2 was negatively correlated with the Interdecadal Pacific Oscillation (IPO) index. Both the 2009/10 and 2015/16 El Niño events and an increasing phase of IPO contributed to this long pCO2 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 pCO2 in the Niño 3.4 region. Our results imply a significant impact of climate variabilities on sea surface pCO2 in the equatorial Pacific.

Plain Language Summary

The equatorial Pacific Ocean is one of the largest natural sources of carbon dioxide (CO2) to the atmosphere. It can partially reduce the CO2 absorbed by large areas of the ocean. Here we use a series of data sets to investigate the long-term variations in the sea surface partial pressure of CO2 over the equatorial Pacific Ocean. Unlike the increasing trend in the global ocean surface pCO2 due to the continuous increase in atmospheric CO2 impacted by human activities, the equatorial Pacific Ocean features significant long-term variabilities. The pCO2 observations and products that we used support a pCO2 increasing hiatus at the Niño 3.4 region (located in the central and eastern equatorial Pacific Ocean) since 2010. Further analysis found that the hiatus is related to El Niño events and the large-scale, long period oscillation of the Pacific basin. Our results imply the impact of natural climate variabilities on sea surface pCO2 in this important sea area of the equatorial Pacific Ocean.

Qiu S., Feng Y., Zhang Y., Qi D., Wu Y. & Du Y., 2021. A surface pCO2 increasing hiatus in the equatorial Pacific Ocean since 2010. Geophysical Research Letters 48: e2021GL093612. doi: 10.1029/2021GL093612. Article (subscription required).

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