Evidence of shallow- and deep-water gas hydrate destabilizations in North Atlantic polar continental margin sediments

 Destabilization of gas hydrates from the North Atlantic polar continental margins is geophysically detectable within hydrate stability zones (HSZ). High-frequency seismic surveys of structures and propagation velocities of compressional waves have changed the classic conception of a consistently stable hydrate zone. The results are important in two respects: (1) unstable shallow-water gas hydrates can substantially contribute to the transfer of methane into the atmosphere, and (2) deep-water gas hydrates also indicate destabilization, which results in slope instability with probably only a secondary role in the transfer of methane to the atmosphere and thus in the greenhouse effect. Received: 6 August 1997 / Revision received: 26 January 1998