Relevant methane emission to the atmosphere from a geological gas manifestation.

ABSTRACT: Quantifying natural geological sources of methane (CH₄) allows to improve the assessment of anthropogenic emissions to the atmosphere from fossil fuel industries. The global CH₄ flux of geological gas is, however, an object of debate. Recent fossil (¹⁴C-free) CH₄ measurements in preindustrial-era ice cores suggest very low global geological emissions (~?1.6 Tg year^-1), implying a larger fossil fuel industry source. This is however in contrast with previously published bottom-up and top-down geo-emission estimates (~?45 Tg year^-1) and even regional-scale emissions of ~?1-2 Tg year^-1. Here we report on significant geological CH₄ emissions from the Lusi hydrothermal system (Indonesia), measured by ground-based and satellite (TROPOMI) techniques. Both techniques indicate a total CH₄ output of ~?0.1 Tg year^-1, equivalent to the minimum value of global geo-emission derived by ice core ¹⁴CH₄ estimates. Our results are consistent with the order of magnitude of the emission factors of large seeps used in global bottom-up estimates, and endorse a substantial contribution from natural Earth's CH₄ degassing. The preindustrial ice core assessments of geological CH₄ release may be underestimated and require further study. Satellite measurements can help to test geological CH₄ emission factors and explain the gap between the contrasting estimates.

SUBMITTER: Mazzini A 

PROVIDER: S-EPMC7892996 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature