Methane emission from Arctic shelf sediments when hydrate stability conditions are violated
V.V. Malakhova
Institute of Computational Mathematics and Mathematical Geophysics of the Siberian Branch of the RAS, Novosibirsk, Russia
Keywords: methane emission, Arctic, methane hydrate stability zone, numerical simulation
Abstract
Based on numerical simulation, we have estimated the thickness and spatial distribution of the methane hydrate stability zone (MHSZ) associated with submarine permafrost. Using CMIP6 ensemble model results under a scenario of high anthropogenic greenhouse gas emissions (SSP5-8.5), we find that the shrinkage of the MHSZ weakly depends on ongoing warming and occurs mainly on the lower boundary side. This process is mainly a consequence of the Holocene marine transgression and depends on the intensity of the geothermal flux. The spatial distribution of the methane fluxes from the bottom sediments as a consequence of the degradation of gas hydrates under the violation of their conditions of existence has been obtained. The estimated intensity of methane emission from the seafloor to the water was 15 Tg per year for the modern period and 16-17 Tg per year up to 2300 (similar estimates for the intensity of emission from the water to the atmosphere were not made in this work). Significant changes in the intensity of methane emissions from the seafloor to the water are not likely for at least several thousand years. The resulting fields of methane fluxes from bottom sediments can be used in numerical ocean models to estimate methane emissions to the atmosphere.
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