Unusual characteristics of the carbon cycle during the 2015−2016 El Niño

Kai Wang; Xuhui Wang; Shilong Piao; Frédéric Chevallier; Jiafu Mao; Xiaoying Shi; Chris Huntingford; Ana Bastos; Philippe Ciais; Hao Xu; Ralph F. Keeling; Stephen W. Pacala; Anping Chen

doi:10.1111/gcb.15669

Unusual characteristics of the carbon cycle during the 2015−2016 El Niño

Kai Wang, Xuhui Wang, Shilong Piao, Frédéric Chevallier, Jiafu Mao, Xiaoying Shi, Chris Huntingford, Ana Bastos, Philippe Ciais, Hao Xu, Ralph F. Keeling, Stephen W. Pacala, Anping Chen

Earth Systems Modeling

Research output: Contribution to journal › Article › peer-review

7 Scopus citations

Abstract

The 2015−2016 El Niño was one of the strongest on record, but its influence on the carbon balance is less clear. Using Northern Hemisphere atmospheric CO₂ observations, we found both detrended atmospheric CO₂ growth rate (CGR) and CO₂ seasonal-cycle amplitude (SCA) of 2015−2016 were much higher than that of other El Niño events. The simultaneous high CGR and SCA were unusual, because our analysis of long-term CO₂ observations at Mauna Loa revealed a significantly negative correlation between CGR and SCA. Atmospheric inversions and terrestrial ecosystem models indicate strong northern land carbon uptake during spring but substantially reduced carbon uptake (or high emissions) during early autumn, which amplified SCA but also resulted in a small anomaly in annual carbon uptake of northern ecosystems in 2015−2016. This negative ecosystem carbon uptake anomaly in early autumn was primarily due to soil water deficits and more litter decomposition caused by enhanced spring productivity. Our study demonstrates a decoupling between seasonality and annual carbon cycle balance in northern ecosystems over 2015−2016, which is unprecedented in the past five decades of El Niño events.

Original language	English
Pages (from-to)	3798-3809
Number of pages	12
Journal	Global Change Biology
Volume	27
Issue number	16
DOIs	https://doi.org/10.1111/gcb.15669
State	Published - Aug 2021

Funding

We thank Dr. Pieter Tans and Dr. Ed Dlugokencky for providing the CO mole fraction data. We also thank the TRENDYv6 modelers for their simulations and Dr. Christian Rödenbeck for the Jena CarboScope inversion datasets. This study was supported by the National Natural Science Foundation of China (grant nos. 41861134036 and 41988101) and an Oak Ridge National Lab subcontract (grant no. 4000167205). J. Mao and X. Shi were supported by the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation Science Focus Area and the Terrestrial Ecosystem Science Scientific Focus Area project in the Earth and Environmental Systems Sciences Division of the Biological and Environmental Research (BER) office in the US Department of Energy Office of Science. Oak Ridge National Laboratory is supported by the Office of Science of the US Department of Energy under contract no. DE‐AC05‐00OR22725. 2

Funders	Funder number
Oak Ridge National Lab subcontract	4000167205
Synthesis and Computation Science Focus Area
U.S. Department of Energy	DE‐AC05‐00OR22725
Office of Science
Biological and Environmental Research
National Natural Science Foundation of China	41988101, 41861134036

Keywords

CO seasonal-cycle amplitude (SCA)
El Niño
atmospheric CO growth rate (CGR)
net biome productivity (NBP)
northern terrestrial ecosystems
soil water deficit

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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title = "Unusual characteristics of the carbon cycle during the 2015−2016 El Ni{\~n}o",

abstract = "The 2015−2016 El Ni{\~n}o was one of the strongest on record, but its influence on the carbon balance is less clear. Using Northern Hemisphere atmospheric CO2 observations, we found both detrended atmospheric CO2 growth rate (CGR) and CO2 seasonal-cycle amplitude (SCA) of 2015−2016 were much higher than that of other El Ni{\~n}o events. The simultaneous high CGR and SCA were unusual, because our analysis of long-term CO2 observations at Mauna Loa revealed a significantly negative correlation between CGR and SCA. Atmospheric inversions and terrestrial ecosystem models indicate strong northern land carbon uptake during spring but substantially reduced carbon uptake (or high emissions) during early autumn, which amplified SCA but also resulted in a small anomaly in annual carbon uptake of northern ecosystems in 2015−2016. This negative ecosystem carbon uptake anomaly in early autumn was primarily due to soil water deficits and more litter decomposition caused by enhanced spring productivity. Our study demonstrates a decoupling between seasonality and annual carbon cycle balance in northern ecosystems over 2015−2016, which is unprecedented in the past five decades of El Ni{\~n}o events.",

keywords = "CO seasonal-cycle amplitude (SCA), El Ni{\~n}o, atmospheric CO growth rate (CGR), net biome productivity (NBP), northern terrestrial ecosystems, soil water deficit",

author = "Kai Wang and Xuhui Wang and Shilong Piao and Fr{\'e}d{\'e}ric Chevallier and Jiafu Mao and Xiaoying Shi and Chris Huntingford and Ana Bastos and Philippe Ciais and Hao Xu and Keeling, {Ralph F.} and Pacala, {Stephen W.} and Anping Chen",

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doi = "10.1111/gcb.15669",

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AU - Wang, Kai

AU - Wang, Xuhui

AU - Piao, Shilong

AU - Chevallier, Frédéric

AU - Mao, Jiafu

AU - Shi, Xiaoying

AU - Huntingford, Chris

AU - Bastos, Ana

AU - Ciais, Philippe

AU - Xu, Hao

AU - Keeling, Ralph F.

AU - Pacala, Stephen W.

AU - Chen, Anping

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N2 - The 2015−2016 El Niño was one of the strongest on record, but its influence on the carbon balance is less clear. Using Northern Hemisphere atmospheric CO2 observations, we found both detrended atmospheric CO2 growth rate (CGR) and CO2 seasonal-cycle amplitude (SCA) of 2015−2016 were much higher than that of other El Niño events. The simultaneous high CGR and SCA were unusual, because our analysis of long-term CO2 observations at Mauna Loa revealed a significantly negative correlation between CGR and SCA. Atmospheric inversions and terrestrial ecosystem models indicate strong northern land carbon uptake during spring but substantially reduced carbon uptake (or high emissions) during early autumn, which amplified SCA but also resulted in a small anomaly in annual carbon uptake of northern ecosystems in 2015−2016. This negative ecosystem carbon uptake anomaly in early autumn was primarily due to soil water deficits and more litter decomposition caused by enhanced spring productivity. Our study demonstrates a decoupling between seasonality and annual carbon cycle balance in northern ecosystems over 2015−2016, which is unprecedented in the past five decades of El Niño events.

AB - The 2015−2016 El Niño was one of the strongest on record, but its influence on the carbon balance is less clear. Using Northern Hemisphere atmospheric CO2 observations, we found both detrended atmospheric CO2 growth rate (CGR) and CO2 seasonal-cycle amplitude (SCA) of 2015−2016 were much higher than that of other El Niño events. The simultaneous high CGR and SCA were unusual, because our analysis of long-term CO2 observations at Mauna Loa revealed a significantly negative correlation between CGR and SCA. Atmospheric inversions and terrestrial ecosystem models indicate strong northern land carbon uptake during spring but substantially reduced carbon uptake (or high emissions) during early autumn, which amplified SCA but also resulted in a small anomaly in annual carbon uptake of northern ecosystems in 2015−2016. This negative ecosystem carbon uptake anomaly in early autumn was primarily due to soil water deficits and more litter decomposition caused by enhanced spring productivity. Our study demonstrates a decoupling between seasonality and annual carbon cycle balance in northern ecosystems over 2015−2016, which is unprecedented in the past five decades of El Niño events.

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KW - El Niño

KW - atmospheric CO growth rate (CGR)

KW - net biome productivity (NBP)

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KW - soil water deficit

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Unusual characteristics of the carbon cycle during the 2015−2016 El Niño

Abstract

Funding

Keywords

UN SDGs

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