TY - JOUR
T1 - Amplification of the Ocean Carbon Sink During El Niños
T2 - Role of Poleward Ekman Transport and Influence on Atmospheric CO2
AU - Liao, Enhui
AU - Resplandy, Laure
AU - Liu, Junjie
AU - Bowman, Kevin W.
N1 - Funding Information:
Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We are very thankful to the NOAA‐GFDL team that develops, maintains, and shares the ocean physical MOM6 code and the biogeochemical COBALT code, including A. Adcroft, J. Dunne, B. Hallberg, M. Harrison, and C. Stock. E. L., L. R., K. B., and J. L. gratefully acknowledge the support of the NASA OCO‐2 Science Team Grant 80NSSC18K0893. K. B. and J. L. also acknowledge support from the NASA CMS‐Flux NNH16ZDA001N‐CMS.
Funding Information:
Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We are very thankful to the NOAA-GFDL team that develops, maintains, and shares the ocean physical MOM6 code and the biogeochemical COBALT code, including A. Adcroft, J. Dunne, B. Hallberg, M. Harrison, and C. Stock. E. L., L. R., K. B., and J. L. gratefully acknowledge the support of the NASA OCO-2 Science Team Grant 80NSSC18K0893. K. B. and J. L. also acknowledge support from the NASA CMS-Flux NNH16ZDA001N-CMS.
Publisher Copyright:
© 2020. American Geophysical Union. All Rights Reserved.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Amplification of the ocean carbon sink during El Niño events partially offset terrestrial biosphere carbon losses to the atmosphere, but uncertainties in the magnitude, timing, and spatial extent of the ocean response confound our understanding of the global carbon budget and its sensitivity to climate. Here, we examine the mechanisms controlling the anomalous tropical Pacific Ocean CO2 drawdown during El Niño events harnessing multidecadal ocean pCO2 observations in conjunction with a state-of-the-art ocean biogeochemical model. We show that poleward Ekman transport dramatically amplifies the near-equatorial pCO2 anomaly identified in prior work and that this amplification varies considerably between El Niño events. During central Pacific events, the CO2 flux anomaly can vary up to fourfold between events (2002/2003 vs. 2015/2016), but it always recedes during the boreal winter to spring transition and the poleward transport of the anomaly mostly extends into the Northern Hemisphere. During eastern Pacific events characterized by an equatorially centered intertropical convergence zone (e.g., 1997/1998), the intense CO2 flux anomaly persists into boreal summer and can extend further into the Southern Hemisphere. The hemispheric asymmetry (northward vs. southward extension) and the termination (boreal winter/spring for central Pacific events vs. boreal summer for eastern Pacific events) of the ocean CO2 response are tied to the El Niño dynamics in the near-equatorial region and also how it is amplified by poleward Ekman transport. Finally, we evaluate how differences in the ocean response influence atmospheric CO2 and discuss the potential of atmospheric CO2 satellite data to provide observational constraints.
AB - Amplification of the ocean carbon sink during El Niño events partially offset terrestrial biosphere carbon losses to the atmosphere, but uncertainties in the magnitude, timing, and spatial extent of the ocean response confound our understanding of the global carbon budget and its sensitivity to climate. Here, we examine the mechanisms controlling the anomalous tropical Pacific Ocean CO2 drawdown during El Niño events harnessing multidecadal ocean pCO2 observations in conjunction with a state-of-the-art ocean biogeochemical model. We show that poleward Ekman transport dramatically amplifies the near-equatorial pCO2 anomaly identified in prior work and that this amplification varies considerably between El Niño events. During central Pacific events, the CO2 flux anomaly can vary up to fourfold between events (2002/2003 vs. 2015/2016), but it always recedes during the boreal winter to spring transition and the poleward transport of the anomaly mostly extends into the Northern Hemisphere. During eastern Pacific events characterized by an equatorially centered intertropical convergence zone (e.g., 1997/1998), the intense CO2 flux anomaly persists into boreal summer and can extend further into the Southern Hemisphere. The hemispheric asymmetry (northward vs. southward extension) and the termination (boreal winter/spring for central Pacific events vs. boreal summer for eastern Pacific events) of the ocean CO2 response are tied to the El Niño dynamics in the near-equatorial region and also how it is amplified by poleward Ekman transport. Finally, we evaluate how differences in the ocean response influence atmospheric CO2 and discuss the potential of atmospheric CO2 satellite data to provide observational constraints.
KW - Ekman transport
KW - El Niño events
KW - air-sea CO flux
KW - equatorial upwelling
KW - rainfall dilution effect
KW - tropical Pacific Ocean
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U2 - 10.1029/2020GB006574
DO - 10.1029/2020GB006574
M3 - Article
AN - SCOPUS:85091475894
VL - 34
JO - Global Biogeochemical Cycles
JF - Global Biogeochemical Cycles
SN - 0886-6236
IS - 9
M1 - e2020GB006574
ER -