Process-based modelling of greenhouse gases in lakes: ways to tackle spatial heterogeneity

Abstract:

Lakes are regarded as an important source of methane and carbon dioxide in the atmosphere and awareness of their significance has increased during last years (Bastviken, Tranvik, Downing, Crill, & Enrich-Prast, 2011)⁠. This large observational evidence motivates the development of process-based models for improving global and regional inventories of contemporary CH4 and CO2 fluxes from lacustrine systems and future predictions of these fluxes in coupled Earth System models. For the thermo-hydrodynamic part of such models 1D (in vertical) lake parameterizations widely used in numerical weather prediction and climate modelling (Stepanenko et al., 2013)⁠ seem to be the best candidates. However, a bulk of observations demonstrates a large horizontal heterogeneity of bubble and diffusive methane fluxes in lakes, that may pose a principal difficulty to be simulated in a framework of 1D lake models. Are we able to retain the simplicity of 1D models and realistically capture the difference of carbon fluxes between deep and shallow parts and the total lake flux? Opportunities to solve this problem are discussed in this contribution based on the experience with 1D LAKE model (Stepanenko, Machul’skaya, Glagolev, & Lykossov, 2011)⁠ and 3D Large Eddy Simulation of lake and the atmospheric boundary layer above.

Bastviken, D., Tranvik, L. J., Downing, J. A., Crill, P. M., & Enrich-Prast, A. (2011). Freshwater Methane Emissions Offset the Continental Carbon Sink. Science, 331(6013), 50. doi:10.1126/science.1196808

Stepanenko, V. M., Machul’skaya, E. E., Glagolev, M. V., & Lykossov, V. N. (2011). Numerical modeling of methane emissions from lakes in the permafrost zone. Izvestiya, Atmospheric and Oceanic Physics, 47(2), 252–264. doi:10.1134/S0001433811020113

Stepanenko, V. M., Martynov, A., Jöhnk, K. D., Subin, Z. M., Perroud, M., Fang, X., … Goyette, S. (2013). A one-dimensional model intercomparison study of thermal regime of a shallow, turbid midlatitude lake. Geoscientific Model Development, 6(4), 1337–1352. doi:10.5194/gmd-6-1337-2013

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