Probabilistic Estimates of Global Marine N2O Emissions within the Bern3D Earth System Model of Intermediate Complexity

Nitrous oxide (N₂O) is a radiatively active atmospheric trace gas (currently ~325 ppb, increasing by ~0.25% yr^-1) and is emitted to the atmosphere from poorly constrained microbial processes on land and in the oceans. The latest estimates given by the IPCC for marine N₂O sources range from 1.8-9.4 TgN yr^-1. Marine N₂O production is commonly parameterized as a function of organic matter remineralization, oxygen concentrations, or temperature to account for (chemo-autotrophic) nitrification and (chemo-heterotrophic) denitrification processes. We implemented different production schemes in the cost-efficient Bern3D Earth-System Model of Intermediate Complexity which features a 3-D frictional-geostrophic ocean and an OCMIP2-type marine carbon cycle. We optimize the parameters governing N₂O production in a probabilistic, Monte-Carlo-type, Bayesian framework by applying observed dissolved N₂O data, compiled in the MEMENTO database, as constraints. N₂O emissions of the observation-constrained model ensemble will then be determined for both future and past (e.g. Younger-Dryas) environmental conditions.