Seep carbonate clumped isotopes revealing ocean warming-induced gas hydrate dissociation

Abstract

The dissociation of marine methane hydrates due to the increased ocean temperature may be widespread in the context of global warming. However, direct evidence for this phenomenon is limited. Here, we reported the carbon and oxygen isotopes, mineralogy, elements, and clumped isotopes (Δ47) of coring seep carbonates (MIS5e) to explore the influence of temperature changes on gas hydrate stability. The extremely low δ13C and high δ18O values of bulk carbonates (average, −48.1‰ and 4.4‰, respectively) indicated the authigenic carbonates formed from the anaerobic oxidation of methane and gas hydrate dissociation. An anaerobic environmental condition with intense methane seepages was confirmed by the dominant aragonite, Mo enrichment (MoEF averaged as 312), and positive Ce anomalies (averaged as −0.03). The Δ47 values ranged from 0.714 to 0.745, indicating a higher bottom-water temperature (averaged at 7.5 °C) during MIS5e compared with the current seafloor temperature (5.4 °C). This study provides direct evidence for the dissociation of gas hydrate triggered by ocean warming, presenting new insights into potential temperature-induced gas hydrate instability due to global climate warming.