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Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall

J.F. Bratton
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Abstract

Although submarine methane hydrates or clathrates have been highlighted as potential amplifiers of modern global climate change and associated glacio-eustatic sea-level rise, their potential role in sea-level fall has not been appreciated. Recent estimates of the total volume occupied by gas hydrates in marine sediments vary 20-fold, from 1.2 × 10 14 to 2.4 × 10 15 m 3 . Using a specific volume change on melting of −21%, dissociation of the current global inventory of hydrate would result in a decrease of submarine hydrate volume of 2.4 × 10 13 to 5.0 × 10 14 m 3 . Release of free gas bubbles present beneath hydrates would increase these volumes by 1.1–2.0 × 10 13 m 3 . The combined effects of hydrate melting and subhydrate gas release would result conservatively in a global sea-level fall of 10–146 cm. Such a mechanism may offset some future sea-level rise associated with thermal expansion of the oceans. It could also explain anomalous sea-level drops during ice-free periods such as the early Eocene, the Cretaceous, and the Devonian.

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J.F. Bratton. 1999. Clathrate eustasy: Methane hydrate melting as a mechanism for geologically rapid sea-level fall. https://doi.org/10.1130/0091-7613(1999)027%3C0915%3Acemhma%3E2.3.co%3B2

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