Based on a 3D quasi-geostrophic model of the World Ocean climate, supplemented with the model of the dissolved methane transport by ocean streams, a model describing consequences of possible destabilization of sub-floor methane hydrates in the World Ocean has been developed. The presences of methane and certain thermodynamic conditions, the so-called p,T-conditions, are necessary for the formation of methane hydrates. It is supposed that methane hydrates exist throughout in the sediment layer, where thermobaric conditions are favorable for their existence. To estimate the scale of their destabilization, the model parameter, namely, the depth of methane hydrates occurrence in the World Ocean deposits is important. The sub-floor depth is determined with the account of the thickness of the methane hydrate stability zone, geothermal gradient, sediment layer porosity, and percentage of sediments, the porous space of which contains the gas hydrates.