Seismic Characteristics of the Gas Hydrate System in the Mackenzie Trough of the Canadian Beaufort Sea, Arctic Ocean

Abstract

We present a comprehensive seismic characterization of the gas hydrate system in the outer continental shelf of the Mackenzie Trough, Canadian Beaufort Sea, based on recently acquired multichannel seismic (MCS) data, P‐wave velocity modeling, and 3D thermal modeling. We identified high‐amplitude, reverse‐polarity Bottom‐Simulating Reflections (BSRs) over an area of ∼406 km ² , marking the base of the gas hydrate stability zone (GHSZ). Iterative migration velocity analysis reveals high‐velocity zones (2.0–2.5 km/s) indicative of hydrate‐bearing sediments overlying low‐velocity free gas (1.0–1.6 km/s). Effective‐medium modeling indicates gas hydrate saturations of 12%–67% of pore space, with maxima near the shelf break, and free‐gas saturations of up to 9%. Combined, these estimates yield a potential methane mass of approximately 0.17–0.23 Gt within the Trough. By integrating a 3D heat flow model constrained by local ocean temperatures, we find that the theoretical base of the GHSZ closely matches observed BSR depths, except in the western sector where BSRs are 40–60 m deeper than the modeled GHSZ. This discrepancy implies that the gas hydrate system in the Mackenzie Trough exhibits localized disequilibrium. Furthermore, these findings suggest that the extensive deep‐marine gas hydrate province and its associated localized thermodynamic disequilibrium, documented off the US Alaska margin, may extend eastward to the Mackenzie Trough, which may represent the easternmost documented occurrence along the US‐Canadian Beaufort margin. While this deep hydrate system is unlikely to be undergoing destabilization from recent ocean warming, sustained long‐term climate forcing may pose a latent risk for future gas hydrate dissociation.