Global Soil Consumption of Atmospheric Carbon Monoxide: An Analysis Using a Process-Based Biogeochemistry Model
Atmospheric Chemistry and Physics Discussions
Carbon monoxide (CO) plays an important role in controlling the oxidizing capacity of the atmosphere by reacting with OH radicals that affect atmospheric methane (CH<sub>4</sub>) dynamics. We develop a process-based biogeochemistry model to quantify CO exchange between the soil and the atmosphere at the global scale. The model is parameterized using CO flux data from the field and laboratory experiments for eleven representative ecosystem types. The model is then extrapolated to the global
... to the global terrestrial ecosystems. Global soil gross consumption, gross production, and net flux of the atmospheric CO are estimated to be 132&ndash;154, 29&ndash;36 and 102&ndash;119&thinsp;Tg&thinsp;CO&thinsp;yr<sup>&minus;1</sup> (1&thinsp;Tg&thinsp;=&thinsp;1012&thinsp;g), respectively, assuming a constant spatially distributed atmospheric CO concentration (~&thinsp;128&thinsp;ppbv) during the 20th century. When satellite-based atmospheric CO concentration data are used, our estimates of the soil gross consumption are 180-197 Tg CO yr-1 in the period of 2000&ndash;2013. Tropical evergreen forest, savanna and deciduous forest areas are the largest sinks at 93&thinsp;Tg&thinsp;CO&thinsp;yr<sup>&minus;1</sup>. Soil CO gross consumption is sensitive to air temperature and atmospheric CO concentration while gross production is sensitive to soil organic carbon (SOC) stock and air temperature. Under future climate scenarios, the soil gross consumption, gross production and net flux of CO will increase at 0.15&ndash;1.23, 0.04&ndash;0.3 and 0.12&ndash;0.94&thinsp;Tg&thinsp;CO&thinsp;yr<sup>&minus;2</sup> during 2014&ndash;2100, reaching 162&ndash;194, 36&ndash;44, and 126&ndash;150&thinsp;Tg&thinsp;CO&thinsp;yr<sup>&minus;1</sup> by the end of the 21st century, respectively. Areas near the equator, Eastern US, Europe and eastern Asia will be the largest sinks due to optimum soil moisture and high temperature. The annual global soil net flux of atmospheric CO is primarily controlled by air temperature, soil temperature, SOC and atmospheric CO concentrations, while its monthly variation mainly determined by air temperature, precipitation, soil temperature and soil moisture. Our process-based soil CO dynamics model and analysis shall benefit the modeling of the global climate and atmospheric chemistry.