- Conference Proceedings Paper
Abstract: Large amounts of carbon and nutrients are delivered to the coastal and pelagic ocean by the Land-Ocean Aquatic Continuum (LOAC). The LOAC refers to the major biogeochemical pathway whereby river and groundwater discharge is connected to coastal systems. Terrestrial loads fluxed through the LOAC system likely play a key role in the carbon cycle of the global ocean. For example, riverine carbon export may be responsible for global-ocean outgassing of roughly 0.45 Pg C yr-1. While the significance of terrestrial exports is commonly accepted in the community, quantification of these fluxes over seasonal-to-interannual timescales is still lacking. To address this deficiency, we parameterize contemporary terrestrial carbon and nutrient export in the ECCO-Darwin global-ocean biogeochemistry state estimate and evaluate the subsequent sensitivity of air-sea CO2 fluxes at regional and global scales from 1995 to 2017. We compute daily riverine export by combining the GlobalNEWS2.0 watershed model with point-source freshwater discharge from the JRA55-do atmospheric reanalysis. Additionally, we derive carbon exports from coastal wetlands (i.e., mangroves and marshes) from ecosystem primary production and the associated soil organic carbon. We evaluate our simulated ocean biogeochemistry and air-sea CO2 fluxes using in-situ and remotely-sensed observations in the coastal ocean. We quantify the impact of terrestrial exports to the global ocean by comparing our new simulation with a baseline simulation that does not include terrestrial carbon and nutrient export. Our study highlights the importance of improving the representation of terrestrial fluxes in global-ocean biogeochemistry models for the accurate simulation of ocean carbon cycling, biogeochemistry, and ecology.