Author: Manon O.,B. Maisonnier,  doctoral student (Unniversité Libre de Bruxelles)

Designation: 

Description:
Natural emissions of CH4 from lakes are poorly constrained as shown in the last budget by the Global Carbon Project (Saunois et al., 2020). The extent to which these emissions are impacted by anthropogenic perturbations, particularly warming and eutrophication, are even more quantitatively uncertain, especially on the large scale. This results partly from our limited ability to resolve the complex interplay of the many processes and drivers controlling CH4 cycling in lakes and their spatio-temporal variability. Here, we present a hybrid approach to assess lake CH4 emissions at the European scale. To resolve spatial patterns, we rely on the HydroLAKES dataset coupled with semi-empirical predictors of CH4 emissions derived from nutrient concentrations as computed by a global stochastic-mechanistic model. To superimpose the temporality, we rely on CSLM for the lake physics and embed a new process-based model of the coupled autochthonous C-O2-CH4 dynamics driven by atmospheric forcings and nutrient loads from the catchment. We estimate an annual-mean CH4 emission from European lakes of 2.53±1.0 Tg CH4-C yr-1 for the period 1990-present, with a strong spatial variability resolved at 0.1°x0.1°. The temporal dynamics in the autochthonous C cycle, O2 profiles and diffusive/ebullitive CH4 fluxes is also well captured for lakes of distinct trophic status and geometries and will be scaled-up regionally using a lake clustering approach. Overall, our  lake CH4 emission estimates help reconcile CH4 budgets derived from national inventory-data and atmospheric inversion models.

Category: Scientific Program Abstract > Special Sessions > CS10 Gas Fluxes