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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.

Plain Language Summary Release of greenhouse methane bubbles is often observed at various hydrostatic pressure drops: at low tides, waves, and even at atmospheric pressure drops in marine and lacustrine settings. It is pronounced at the different vent structures, for example, pockmarks, mud volcanoes, and cold seeps. It has been shown that long timescale (glacial to centennial frequency) sea level drops induce a stable bubble ascent and control a position of the gas horizon in muddy aquatic sediment. Bubble escape from the gas horizon is more feasible under shorter-period (internal and surface) waves of higher amplitude travelling in shallow water. In this case the bubble starts a rapid unrestricted ascent and will ultimately be released into the water column. Otherwise, the bubble will migrate in the stable regime remaining close to the gas horizon. These findings are illustrated by examples of various vent structures (e.g., pockmarks), especially emphasized in shallow straits and bays, described in the literature. These important insights improve our understanding of the global carbon cycle in general, and of bubble ascent from the gas horizon in aquatic sediment, in particular.