I wonder if, when referring to "bubbles", they mean pingos... remember them?
Methane now bubbling from Beaufort Sea
Anomalies caused by ancient event

Updated
A search of the GNS website referred to in the link has some information on the gas hydrate research

What are gas hydrates? <= nice structure and phase diagrams

Energy resource

Useful links

I remember the PLF's - Wayne Madsen turned them into a tinfoil horror story back when that news item came out :-)

I like the NZ diagrams.

I'll just add the link to the USGS stability diagram as it is even clearer.

It's a good thing that these formations are deep and that water has a high heat capacity.... It'll probably take a long time for surface heat to penetrate to that depth... especially if/as(?) the oceans stratify...