Quantifying CO2 emissions from a newly created reservoir: FAQ-DNDC (v1.0) model development, testing, and sensitivity analysis

Abstract:

Quantifying greenhouse gas (GHG) emissions from inland water is essential for the global carbon cycle. To quantify GHG emissions from lakes and reservoirs we coupled a lake carbon model (HLCM), a newly developed 1-dimension (1-D) thermal stratification model, and a terrestrial biogeochemistry model (DNDC) that is able to represent soil carbon dynamics under flooded conditions. We present here the first results of the newly coupled model, FAQ-DNDC. We evaluated the model for what mechanisms governs the CO₂ emissions from a newly created shallow boreal reservoir, Eastmain-1, in northern Quebec, Canada. We compared simulated CO₂ fluxes against eddy covariance tower measurements during the period of 2007-2012. The observed peak emissions in spring were simulated because water column might lose the dissolved inorganic carbon (DIC) accumulated through the ice-cover period in winter. The observed and simulated annual CO₂ emissions from the reservoir surface gradually decline with reservoir age. The sensitivity analysis showed that CO₂ emissions in high-latitude shallow reservoirs response strongly to warming owning to shorter ice cover period and higher decomposition rate under a warming scenario. We also found that terrestrial dissolved organic carbon (DOC) input would stimulate CO₂ emissions from the reservoir. We conclude that models of aquatic carbon cycle should link terrestrial carbon cycle to better predicting GHG emissions from aquatic ecosystems and to better understanding the carbon balance of lake-rich regions.