Accelerating CO<sub>2</sub> Outgassing in the Equatorial Pacific from Satellite Remote Sensing
The equatorial Pacific serves as the world’s largest oceanic source of CO<sub>2</sub>. The contrasting ocean environment in the eastern (i.e., upwelling) and western (i.e., warm pool) regions makes it difficult to fully characterize its CO<sub>2</sub> dynamics with limited in...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
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| Series: | Remote Sensing |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2072-4292/17/2/247 |
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| Summary: | The equatorial Pacific serves as the world’s largest oceanic source of CO<sub>2</sub>. The contrasting ocean environment in the eastern (i.e., upwelling) and western (i.e., warm pool) regions makes it difficult to fully characterize its CO<sub>2</sub> dynamics with limited in situ observations. In this study, we addressed this challenge using monthly surface partial pressure of CO<sub>2</sub> (<i>p</i>CO<sub>2</sub>sw) and air-sea CO<sub>2</sub> fluxes (FCO<sub>2</sub>) data products reconstructed from satellite and reanalysis data at a spatial resolution of 1° × 1° in the period of 1982–2021. We found that during the very strong El Niño events (1997/1998, 2015/2016), both <i>p</i>CO<sub>2</sub>sw and FCO<sub>2</sub> showed a significant decrease of 41–58 μatm and 0.5–0.8 mol·m<sup>−2</sup>·yr<sup>−1</sup> in the eastern equatorial Pacific, yet they remained at normal levels in the western equatorial Pacific. In contrast, during the very strong La Niña events (1999/2000, 2007/2008, and 2010/2011), both <i>p</i>CO<sub>2</sub>sw and FCO<sub>2</sub> showed a strong increase of 40–48 μatm and 1.0–1.4 mol·m<sup>−2</sup>·yr<sup>−1</sup> in the western equatorial Pacific, yet with little change in the eastern equatorial Pacific. In the past 40 years, <i>p</i>CO<sub>2</sub>sw in the eastern equatorial Pacific was increasing at a higher rate (2.32–2.51 μatm·yr<sup>−1</sup>) than that in the western equatorial Pacific (1.75 μatm·yr<sup>−1</sup>), resulting in an accelerating CO<sub>2</sub> outgassing (at a rate of 0.03 mol·m<sup>−2</sup>·yr<sup>−2</sup>) in the eastern equatorial Pacific. We comprehensively analyzed the potential effects of different factors, such as sea surface temperature, sea surface wind speed, and Δ<i>p</i>CO<sub>2</sub> in driving CO<sub>2</sub> fluxes in the equatorial Pacific, and found that Δ<i>p</i>CO<sub>2</sub> had the highest correlation (<i>R</i> ≥ 0.80, at <i>p</i> ≤ 0.05), highlighting the importance of accurate estimates of <i>p</i>CO<sub>2</sub>sw from satellites. Further studies are needed to constrain the retrieval accuracy of <i>p</i>CO<sub>2</sub>sw in the equatorial Pacific from satellite remote sensing. |
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| ISSN: | 2072-4292 |