There has been quite a bit of worry about what happens when the methane hydrates on the Arctic shelf go blooie, but a factor not thought of by many is that since these hydrates are underwater, a fair amount of the methane will never reach the surface, but will first go into solution in the sea water, and later be oxidized to CO2, hydrogen carbonate and carbonate ions.
The same issue confronts anyone (Ian, Ian Plimer, are you out there), who rants about all of the carbon dioxide coming from underwater volcanoes. In point of fact, you read it here on Rabett Run, that if such volcanoes really were the source of so much CO2, the easy mark would be to go look for acidic plumes in the ocean. Plimer's hound of the Baskervilles as it were, because they are not found.
Biastoch, et al (eleven of them, including Latif, and Wallman at the University of Kiel, have thought about the fate of the methane hydrates, and in an article entitled "Rising Arctic Ocean temperatures cause gas hydrate destabilization and ocean acidification" conclude that the major effect will be a decrease of pH, near the Arctic Ocean coasts.
Since the Arctic has and will be warmed considerably, Arctic bottom water temperatures and their future evolution projected by a climate model were analyzed. The resulting warming is spatially inhomogeneous, with the strongest impact on shallow regions affected by Atlantic inflow. Within the next 100 years, the warming affects 25% of shallow and mid‐depth regions containing methane hydrates. Release of methane from melting hydrates in these areas could enhance ocean acidification and oxygen depletion in the water column. The impact of methane release on global warming, however, would not be significant within the considered time span.