Weaker regional carbon uptake albeit with stronger seasonal amplitude in northern mid-latitudes estimated by higher resolution GEOS-Chem model

• Published in: The Science of the total environment Vol. 912; p. 169477
• Main Authors: Liu, Zhiqiang, Zeng, Ning, Liu, Yun, Wang, Jun, Han, Pengfei, Cai, Qixiang
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.02.2024
• Subjects: Carbon sink; CO2 inversion; High-resolution transport model; Seasonal amplitude; Seasonal amplitude; Carbon sink; CO2 inversion; High-resolution transport model; CO inversion
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.169477

Terrestrial ecosystem in the Northern Hemisphere is characterized by a substantial carbon sink in recent decades. However, the carbon sink inferred from atmospheric CO2 data is usually larger than process- and inventory-based estimates, resulting in carbon release or near-neutral carbon exchange in the tropics. The atmospheric approach is known to be uncertain due to systematic biases of coarse atmospheric transport model simulation. Compared to a coarse-resolution inverse estimate at 4° × 5° using GEOS-Chem in the integrated region of N. America, E. Asia, and Europe from 2015 to 2018, the annual carbon sink estimate at a native high-resolution of 0.5° × 0.625° is reduced from −3.0±0.08 gigatons of carbon per year (GtC yr−1) to −2.15±0.08 GtC yr−1 due to prominent more carbon release during the non-growing seasons. The major reductions concentrate in the mid-latitudes (20°N–45°N), where the mean land carbon sinks in China and the USA are reduced from 0.64±0.03 and 0.35±0.02 GtC yr−1 to 0.14±0.03 and 0.15±0.02 GtC yr−1, respectively. The coarse-resolution GEOS-Chem tends to trap both the release and uptake signal within the planetary boundary layer, resulting in weaker estimates of biosphere seasonal strength. Since the strong fossil fuel emissions are persistently released from the surface, the trapped signal leads to the stronger estimates of annual carbon uptakes. These results suggest that high-resolution inversion with accurate vertical and meridional transport is urgently needed in targeting national carbon neutrality. [Display omitted] •Coarse resolution GEOS-Chem model tend to weaken the vertical transport, leading to biases in CO2 inversion.•The annual carbon sink estimates at 4°×5° in N. America, E. Asia, and Europe is 40.5 % larger than at 0.5°×0.625°.•The seasonal strength estimates at 4°×5° are smaller than at 0.5°×0.625°, especially during the non-growing seasons.•Generally, the larger carbon uptake occurred in areas with denser fossil fuel emissions.