TY - JOUR
T1 - Consistency and Challenges in the Ocean Carbon Sink Estimate for the Global Carbon Budget
AU - Hauck, Judith
AU - Zeising, Moritz
AU - Le Quéré, Corinne
AU - Gruber, Nicolas
AU - Bakker, Dorothee C.E.
AU - Bopp, Laurent
AU - Chau, Thi Tuyet Trang
AU - Gürses, Özgür
AU - Ilyina, Tatiana
AU - Landschützer, Peter
AU - Lenton, Andrew
AU - Resplandy, Laure
AU - Rödenbeck, Christian
AU - Schwinger, Jörg
AU - Séférian, Roland
N1 - Funding Information:
The Surface Ocean CO2 Atlas (SOCAT) is an international effort, endorsed by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmosphere Study (SOLAS) and the Integrated Marine Biosphere Research (IMBeR) program, to deliver a uniformly quality-controlled surface ocean CO2 database. The many researchers and funding agencies responsible for the collection of data and quality control are thanked for their contributions to SOCAT. We thank Amanda Fay and Marion Gehlen for discussions on technical aspects of the ocean carbon sink estimate and its evaluation and two reviewers for their constructive comments. JH thanks Cara Nissen and Hanna Ewen for their contributions to the plotting scripts. Funding. This research has received funding from the Helmholtz Young Investigator Group Marine Carbon and Ecosystem Feedbacks in the Earth System (MarESys), grant number VH-NG-1301, the European Union's Horizon 2020 research and innovation programme under grant agreement nos. 820989 (COMFORT), 821003 (4C), and 730944 (RINGO). CL received funding from the UK Natural Environment Research Council SONATA project (no. NE/P021417/1). LB received funding from the ANR project SOBUMS (ANR-16-CE01-0014) and from the Chanel Research Chair. LR gratefully acknowledged the support of the Sloan Foundation Research Fellowship program. JS acknowledged funding from the Research Council of Norway through project INES (270061) and HPC resources provided by the National Infrastructure for HPC and Data Storage in Norway, UNINETT Sigma2 (nn/ns2980k).
Funding Information:
This research has received funding from the Helmholtz Young Investigator Group Marine Carbon and Ecosystem Feedbacks in the Earth System (MarESys), grant number VH-NG-1301, the European Union’s Horizon 2020 research and innovation programme under grant agreement nos. 820989 (COMFORT), 821003 (4C), and 730944 (RINGO). CL received funding from the UK Natural Environment Research Council SONATA project (no. NE/P021417/1). LB received funding from the ANR project SOBUMS (ANR-16-CE01-0014) and from the Chanel Research Chair. LR gratefully acknowledged the support of the Sloan Foundation Research Fellowship program. JS acknowledged funding from the Research Council of Norway through project INES (270061) and HPC resources provided by the National Infrastructure for HPC and Data Storage in Norway, UNINETT Sigma2 (nn/ns2980k).
Publisher Copyright:
© Copyright © 2020 Hauck, Zeising, Le Quéré, Gruber, Bakker, Bopp, Chau, Gürses, Ilyina, Landschützer, Lenton, Resplandy, Rödenbeck, Schwinger and Séférian.
PY - 2020/10/27
Y1 - 2020/10/27
N2 - Based on the 2019 assessment of the Global Carbon Project, the ocean took up on average, 2.5 ± 0.6 PgC yr−1 or 23 ± 5% of the total anthropogenic CO2 emissions over the decade 2009–2018. This sink estimate is based on simulation results from global ocean biogeochemical models (GOBMs) and is compared to data-products based on observations of surface ocean pCO2 (partial pressure of CO2) accounting for the outgassing of river-derived CO2. Here we evaluate the GOBM simulations by comparing the simulated surface ocean pCO2 to observations. Based on this comparison, the simulations are well-suited for quantifying the global ocean carbon sink on the time-scale of the annual mean and its multi-decadal trend (RMSE <20 μatm), as well as on the time-scale of multi-year variability (RMSE <10 μatm), despite the large model-data mismatch on the seasonal time-scale (RMSE of 20–80 μatm). Biases in GOBMs have a small effect on the global mean ocean sink (0.05 PgC yr−1), but need to be addressed to improve the regional budgets and model-data comparison. Accounting for non-mapped areas in the data-products reduces their spread as measured by the standard deviation by a third. There is growing evidence and consistency among methods with regard to the patterns of the multi-year variability of the ocean carbon sink, with a global stagnation in the 1990s and an extra-tropical strengthening in the 2000s. GOBMs and data-products point consistently to a shift from a tropical CO2 source to a CO2 sink in recent years. On average, the GOBMs reveal less variations in the sink than the data-based products. Despite the reasonable simulation of surface ocean pCO2 by the GOBMs, there are discrepancies between the resulting sink estimate from GOBMs and data-products. These discrepancies are within the uncertainty of the river flux adjustment, increase over time, and largely stem from the Southern Ocean. Progress in our understanding of the global ocean carbon sink necessitates significant advancement in modeling and observing the Southern Ocean carbon sink including (i) a game-changing increase in high-quality pCO2 observations, and (ii) a critical re-evaluation of the regional river flux adjustment.
AB - Based on the 2019 assessment of the Global Carbon Project, the ocean took up on average, 2.5 ± 0.6 PgC yr−1 or 23 ± 5% of the total anthropogenic CO2 emissions over the decade 2009–2018. This sink estimate is based on simulation results from global ocean biogeochemical models (GOBMs) and is compared to data-products based on observations of surface ocean pCO2 (partial pressure of CO2) accounting for the outgassing of river-derived CO2. Here we evaluate the GOBM simulations by comparing the simulated surface ocean pCO2 to observations. Based on this comparison, the simulations are well-suited for quantifying the global ocean carbon sink on the time-scale of the annual mean and its multi-decadal trend (RMSE <20 μatm), as well as on the time-scale of multi-year variability (RMSE <10 μatm), despite the large model-data mismatch on the seasonal time-scale (RMSE of 20–80 μatm). Biases in GOBMs have a small effect on the global mean ocean sink (0.05 PgC yr−1), but need to be addressed to improve the regional budgets and model-data comparison. Accounting for non-mapped areas in the data-products reduces their spread as measured by the standard deviation by a third. There is growing evidence and consistency among methods with regard to the patterns of the multi-year variability of the ocean carbon sink, with a global stagnation in the 1990s and an extra-tropical strengthening in the 2000s. GOBMs and data-products point consistently to a shift from a tropical CO2 source to a CO2 sink in recent years. On average, the GOBMs reveal less variations in the sink than the data-based products. Despite the reasonable simulation of surface ocean pCO2 by the GOBMs, there are discrepancies between the resulting sink estimate from GOBMs and data-products. These discrepancies are within the uncertainty of the river flux adjustment, increase over time, and largely stem from the Southern Ocean. Progress in our understanding of the global ocean carbon sink necessitates significant advancement in modeling and observing the Southern Ocean carbon sink including (i) a game-changing increase in high-quality pCO2 observations, and (ii) a critical re-evaluation of the regional river flux adjustment.
KW - anthropogenic CO
KW - ocean carbon cycle model evaluation
KW - ocean carbon uptake
KW - riverine carbon flux
KW - seasonal cycle
KW - variability of the ocean carbon sink
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U2 - 10.3389/fmars.2020.571720
DO - 10.3389/fmars.2020.571720
M3 - Article
AN - SCOPUS:85095860104
SN - 2296-7745
VL - 7
JO - Frontiers in Marine Science
JF - Frontiers in Marine Science
M1 - 571720
ER -