56 / 2024-09-03 20:39:39

Simulation Study on the Production, Distribution, and Flux of Global Marine Nitrous Oxide (N2O) - Based on CESM2

Nitrous Oxide,Earth System Model,Marine biogeochemistry

Session 11 - Recent Advances in Modelling the Ocean Carbon Cycle Across Scales

Nitrous oxide (N2O) is an important greenhouse gas with a strong global warming potential. In addition, the increasing concentration of N2O in the atmosphere caused by human activities has an important impact on the global climate system, and nitrous oxide is regarded as the biggest threat of ozone layer destruction in the 21st century. The concentration of N2O in the atmosphere is driven by a natural balance between terrestrial and Marine sources. The Intergovernmental Panel on Climate Change reports that the oceans contribute about 3.8Tg N of N2O per year, or about 21 percent of total N2O emissions. In practice, N2O emissions in the open ocean occur primarily in high-productivity, low-oxygen regions, but the rates of N2O production and consumption in these regions are difficult to measure and therefore difficult to model. In addition, the uncertainty in the determination of N2O emissions in these regions is greater than 100% due to the lack of observational data in the field and the poorly understood mechanism of N2O formation. The process of N2O production in the ocean is complex and dependent on oxygen. When organic matter is remineralized by microorganisms in the ocean interior, N2O is produced in a process associated with the decomposition of organic nitrogen. Given these complexities, the establishment of methods to model ocean N2O production and flux has so far been incomplete, and its distribution and contribution to the global nitrogen cycle have not been well revealed and predicted. In this study, two parameterizations of n2o production and air-sea exchange are included in the Community Earth System Model Version 2-Marine Biogeochemistry Library (CESM2-MARBL), assuming that nitrification is the main N2O generation pathway. Simulation results show that N2O shows high emission fluxes in areas such as the equatorial and eastern tropical Pacific, the northern Indian Ocean, the Northwest Pacific, the North Atlantic and the Agulhas Current.  The large-scale distribution of N2O fluxes in the global ocean is consistent with simulations from other large-scale circulation models as well as measurements, , which is a natural result of relatively high nitrification. Our simulation results reveal tight coupling between the marine carbon cycle, O2, N2O, and climate.