Mid-Atlantic US observations of radiocarbon in CO 2 : fossil and biogenic source partitioning and model evaluation
Abstract
Accurately quantifying regional anthropogenic CO₂ fluxes is fundamental to improving our understanding of the carbon cycle and for creating effective carbon mitigation policies, and the radiocarbon to total carbon ratio in atmospheric CO₂(Δ¹⁴CO₂) is a robust tracer of fossil fuel CO₂ that can discriminate between biogenic and fossil fuel CO₂ sources. NASA's Atmospheric Carbon and Transport-America (ACT-America) airborne mission between 2016 and 2019 aimed to improve the accuracy of regional greenhouse gas flux estimates, through refining our understanding and characterization of fluxes and flux uncertainties in models. Δ¹⁴CO₂ observations from 26 flights are presented for examining seasonal CO₂ source partitioning in the Mid-Atlantic USA. Observed variability in boundary layer CO₂ at timescales ranging from intra-day to seasonal was largely driven by biogenic CO₂ (CO2bio) variability that ranged from −19.7 ppm in summer to 16.2 ppm in fall, while fossil fuel CO₂ (CO2ff) variability remained at 3.3±2.0 ppm. Carbonyl sulfide uptake was well-correlated with CO2bio uptake, and examining this relationship, as well as that between CO₂ and CO2bio variability reinforces the seasonal extent of gross primary productivity response throughout ACT-America. We use airborne Δ¹⁴CO₂ flask sampling alongside in situ carbon monoxide measurements to calculate high-frequency CO2ff and evaluate the magnitude and diurnal variability of modeled CO2ff, deducing likely transport errors in an example flight. Although ACT-America CO2ff signals were attenuated due to the broad source regions sampled, results illustrate the value of Δ¹⁴CO₂ sampling and observation-based methodologies for regional CO₂ flux attribution, evaluation and improvement of modeled CO₂.
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BibTeX
@article{baier2026midatlantic,
title = {{Mid-Atlantic US observations of radiocarbon in CO 2 : fossil and biogenic source partitioning and model evaluation}},
author = {Bianca C Baier and John B Miller and Colm Sweeney and Scott J Lehman and Chad Wolak and Joshua P Digangi and Yonghoon Choi and Kenneth Davis and Sha Feng and Thomas Lauvaux},
journal = {Atmospheric Chemistry and Physics},
year = {2026},
month = oct,
doi = {10.5194/acp-25-10479-2025},
url = {https://hal.science/hal-05807002v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Mid-Atlantic US observations of radiocarbon in CO 2 : fossil and biogenic source partitioning and model evaluation
AU - Bianca C Baier
AU - John B Miller
AU - Colm Sweeney
AU - Scott J Lehman
AU - Chad Wolak
AU - Joshua P Digangi
AU - Yonghoon Choi
AU - Kenneth Davis
AU - Sha Feng
AU - Thomas Lauvaux
PY - 2026
DA - 2026/10/19
JO - Atmospheric Chemistry and Physics
DO - 10.5194/acp-25-10479-2025
UR - https://hal.science/hal-05807002v1
AB - Accurately quantifying regional anthropogenic CO₂ fluxes is fundamental to improving our understanding of the carbon cycle and for creating effective carbon mitigation policies, and the radiocarbon to total carbon ratio in atmospheric CO₂(Δ¹⁴CO₂) is a robust tracer of fossil fuel CO₂ that can discriminate between biogenic and fossil fuel CO₂ sources. NASA's Atmospheric Carbon and Transport-America (ACT-America) airborne mission between 2016 and 2019 aimed to improve the accuracy of regional greenhouse gas flux estimates, through refining our understanding and characterization of fluxes and flux uncertainties in models. Δ¹⁴CO₂ observations from 26 flights are presented for examining seasonal CO₂ source partitioning in the Mid-Atlantic USA. Observed variability in boundary layer CO₂ at timescales ranging from intra-day to seasonal was largely driven by biogenic CO₂ (CO2bio) variability that ranged from −19.7 ppm in summer to 16.2 ppm in fall, while fossil fuel CO₂ (CO2ff) variability remained at 3.3±2.0 ppm. Carbonyl sulfide uptake was well-correlated with CO2bio uptake, and examining this relationship, as well as that between CO₂ and CO2bio variability reinforces the seasonal extent of gross primary productivity response throughout ACT-America. We use airborne Δ¹⁴CO₂ flask sampling alongside in situ carbon monoxide measurements to calculate high-frequency CO2ff and evaluate the magnitude and diurnal variability of modeled CO2ff, deducing likely transport errors in an example flight. Although ACT-America CO2ff signals were attenuated due to the broad source regions sampled, results illustrate the value of Δ¹⁴CO₂ sampling and observation-based methodologies for regional CO₂ flux attribution, evaluation and improvement of modeled CO₂.
SN - 1680-7316
SN - 1680-7324
ER -