Multi-scale response of natural gas hydrate systems to climate warming in the Okinawa Trough cold seep region

The Okinawa Trough, an active back-arc basin in the western Pacific, hosts vast natural-gas-hydrate reserves whose dissociation-driven methane seepage exerts a non-negligible influence on the global carbon cycle. We constructed a bottom-water temperature (BWT) time series from the Last Glacial Maximum (LGM) to 2100 AD, and combined it with numerical modules (hydrate phase-equilibrium, stability-zone distribution, and resource empirical models) to quantify the multi-scale impacts of BWT rise and sea-level change on hydrate stability. Results show that in the LGM (1.94 ± 0.8 °C), the gas hydrate stability zone (GHSZ) extended to 82.7 ± 14.8 m below seafloor and the hydrate inventory totaled to 0.17 ± 0.03 Gt. After LGM, although a 150-m sea-level rise supplied hydrostatic compensation that offset ～60 % of the warming effect on hydrate stability, a BWT increase of 2.1 ± 0.4 °C triggered dissociation, reducing the inventory to 0.14 ± 0.02 Gt by 1985. In recent decades, accelerating global warming has raised BWT from 3.5 ± 1.09 °C to 4.5 ± 0.82 °C, shoaling the GHSZ by ～3.3 m and eroding the hydrate mass by 21%. Coupled with CMIP6 climate projections, we estimated that BWT would reach 6.6 ± 0.93 °C by 2100 AD, thinning the GHSZ to 61.6 ± 4.8 m and shrinking the resource to 0.05 ± 0.01 Gt. This study unveils the response mechanism of Okinawa Trough hydrates to climatic warming and highlights their potential contribution as a regional carbon source to the global budget, providing critical constraints on climate-model refinement and ecological-risk assessment.