Vast amounts of methane hydrates are stored in sediments along the continental margins. Their stability is due to the low temperature–high-pressure conditions found on the seafloor. Global warming could destabilize these hydrates and cause a release of methane (CH4) into the water column and possibly the atmosphere. Since the Arctic has and will be warmed considerably, Arctic bottom water temperatures and their future evolution projected by a climate model were analyzed in a joint modeling effort by a group of physical and biological oceanographers, geologists, geochemists, and atmospheric scientists from the Cluster (A2). The seafloor warming was found to be spatially inhomogeneous, with the strongest impact on shallow regions affected by Atlantic inflow (see Fig.). Within the next 100 years, the warming will affect 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 through aerobic microbial consumption in the water column. Contrary to wide spread previous estimates, the impact of methane release on global warming, however, was found to be insignificant within the time span considered.

Reference:
Biastoch, A., Treude, T., Rüpke, L.H., Riebesell, U., Roth, C., Burwicz, E.B., Park, W., Latif, M., Böning, C.W., Madec, G., Wallmann, K. (2011) Rising Arctic Ocean temperatures cause gas hydrate destabilization and ocean acidification. Geophys. Res. Lett. 38, L08602, doi: 10.1029/2011GL047222

Caption: Impact of Global warming on Arctic methane hydrates within the next 100 years: (a) bottom temperatures in an ocean model (ORCA05), (b) changes due to global warming (KCM), (c) changes in the thickness of the gas hydrate stability zone (geophysical model), (d) changes in the near-bottom pH values by released methane (geochemical calculation). All figures from Biastoch et al. (2011).