Degradation of Terrestrial Organic Carbon and its Effect on the Air-Sea CO2 Exchange

Filippa Fransner1,2, Erik Gustafsson3, Letizia Tedesco4, Marc C. Geibel2,5, Robinson Hordoir2,6, Fabien Roquet1,2, Jonas Nycander1,2, Christoph Humborg3,7, Carl-Magnus Mörth2,8 and Marcello Vichi9, (1)Stockholm University, Department of Meteorology, Stockholm, Sweden, (2)Bolin Centre for Climate Research, Stockholm, Sweden, (3)Stockholm University, Baltic Sea Centre, Stockholm, Sweden, (4)Finnish Environment Institute, Marine Research Centre, Helsinki, Finland, (5)Stockholm University, Dept. of Environmental Science and Analytical Chemistry, Stockholm, Sweden, (6)Swedish Meteorological & Hydrological Institute, Oceanography Research Dept., Norrköping, Sweden, (7)Bolin Centre for Climate Research, Baltic Sea Centre, Stockholm, Sweden, (8)Stockholm University, Department of Geological Sciences, Stockholm, Sweden, (9)University of Cape Town, Department of Oceanography and Marine Research Institute, Cape Town, South Africa
Abstract:
It is becoming more evident that organic matter brought to the oceans by rivers is undergoing a large transformation in the coastal seas. Here we use 3D coupled physical-biogeochemical model (NEMO-Nordic-BFM) for the Northern Baltic Sea, in combination with pCO2 measurements, to investigate to what extent terrestrial organic carbon is degraded into dissolved inorganic carbon (DIC). The effects of physical properties of the sea water, total alkalinity, primary production and degradation, on the outgassing of CO2 are separated in a suite of experiments. It was found that a degradation of terrestrial dissolved organic carbon (DOC) into DIC is needed in order to obtain the high pCO2 values observed close to the coast. A good fit with the observed pCO2 values is obtained when 80% of the terrestrial DOC is degraded relatively fast (decaying time scale of 1 year), which is in good agreement with previous modeling studies.
Back to: Understanding the Coastal Carbon Cycle and Biogeochemical Processes in the Coastal Ocean: Observations and Modeling II