Methane Emission from Arctic Shelf Sediments upon Violation of Hydrate Stability Conditions

Abstract

The thickness and spatial distribution of a methane hydrate stability zone (MHSZ) associated with submarine permafrost is estimated based on numerical simulation. Using CMIP6 ensemble model calculations with a scenario of high anthropogenic greenhouse gas emissions (SSP5-8.5), a weak dependence of MHSZ shrinkage on ongoing warming is found, and mainly on the side of its base. This process is, first of all, a consequence of the Holocene marine transgression and depends on geothermal flux intensity. The spatial distribution of methane fluxes from bottom sediments caused by degradation of gas hydrates under the violation of their existence conditions is derived. The intensity of methane emission from seafloor to water is estimated at 15 Tg/yr in the modern period and 16–17 Tg/yr to 2300 (similar estimates of the intensity of methane emission from water to the atmosphere are not made in this work). Significant changes in the intensity of methane emissions from seafloor to water are hardly probable for at least several thousand years. The resulting fields of methane fluxes from bottom sediments can be used in numerical ocean models for assessing methane emissions to the atmosphere.