Methane Bubble Escape From Gas Horizon in Muddy Aquatic Sediment Under Periodic Wave Loading

Ebullition of greenhouse methane (CH₄) from the aquatic sediments is often observed at various hydrostatic pressure drops: at low tides, waves, and even at atmospheric pressure drops. It is especially pronounced at the different vent structures, for example, pockmarks, mud volcanoes, and cold seeps. The modeling conducted in the current study suggests that long timescale (glacial to centennial frequency) sea level drops may induce “stable” bubble ascent and control the position of the gas horizon in muddy aquatic sediment. Bubbles escape in the “dynamic” regime from the shallow gas horizon and subsequently to the water column is more feasible under shorter-period waves of higher amplitude travelling in shallow water. These findings are illustrated by examples of various vent structures (e.g., pockmarks), pronounced in shallow straits and bays, described in the literature.