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We present a marine two-phase gas model in one dimension (M2PG1) resolving interaction between the free and dissolved gas phases and the gas propagation toward the atmosphere in aquatic environments. The motivation for the model development was to improve the understanding of benthic methane seepage impact on aquatic environments and its effect on atmospheric greenhouse gas composition. Rising, dissolution, and exsolution of a wide size-range of bubbles comprising several gas species are modeled simultaneously with the evolution of the aqueous gas concentrations. A model sensitivity analysis elucidates the relative importance of process parameterizations and environmental effects on the gas behavior. The parameterization of transfer velocity across bubble rims has the greatest influence on the resulting gas distribution, and bubble sizes are critical for predicting the fate of emitted bubble gas. High salinity increases the rise height of bubbles; whereas temperature does not significantly alter it. Vertical mixing and aerobic oxidation play insignificant roles in environments where advection is important. The model, applied in an Arctic Ocean methane seepage location, showed good agreement with acoustically derived bubble rise heights and in situ sampled methane concentration profiles. Coupled with numerical ocean circulation and biogeochemical models, M2PG1 could predict the impact of benthic methane emissions on the marine environment and the atmosphere on long time scales and large spatial scales. Because of its flexibility, M2PG1 can be applied in a wide variety of environmental settings and future M2PG1 applications may include gas leakage from seafloor installations and bubble injection by wave action. The importance of natural and anthropogenic methane (CH4) emissions to the atmosphere has been increasingly recognized in the last few decades as CH4 contributes to greenhouse warming by about 20% (Edenhofer et al. 2014; Pachauri et al. 2014), because CH4 is 32 times more potent than CO2 in terms of warming potential (Pachauri et al. 2014). Large CH4 reservoirs in the form of hydrates, a crystalline structure comprising water molecules encapsulating guest molecules such as CO2 and hydrocarbons (Sloan and Koh 2007), exist in sediments along continental margins worldwide. They are presently estimated to contain 1800 Gt of carbon (Ruppel and Kessler 2016), equivalent to one sixth of the global mobile carbon pool. Hydrates are stable under high pressure and low temperature, suggesting that bottom water warming potentially dissociates hydrates at the boundary of their stability (Westbrook et al. 2009). Yearly global flux of CH4 to the atmosphere associated with dissociation of hydrate deposits is presently estimated at 6 Tg, which amounts to less than 1% of the total CH4 flux to the atmosphere (Kirschke et al. 2013), but hydrate dissociation rates may increase as ocean bottom water temperatures increase over human time scales (Ferré et al. 2012). A substantial amount of CH4 is also found trapped where permafrost (water ice that is frozen all year) caps exist. Gaseous CH4 trapped under hydrate and permafrost caps is presently released through the water column and to the atmosphere on the East Siberian Shelf as the caps become more and more permeable as a result of thawing (Shakhova et al. 2010). In the light of a rapidly warming Arctic Ocean, it is therefore crucial to understand the transport mechanisms of *Correspondence: [email protected] Additional Supporting Information may be found in the online version of this article. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.