sam
Good, I'm glad you have that info.
I've long wondered about sea level and the pressure on "continental shelf" clathrates.
I posted that info on sagg several years back.
it is something that shouldnt be overlooked and Im glad that
you now have that info also.
heres a phase diagram.
Im not certain about the degree of water temperature increase
that could be expected if the currents were to diminish that
carry cold water from the poles to cool the oceans but it looks
like it would take quite a bit of warming to affect the methane clathrates.
lets remember that with added water pressures there will be a
corresponding increase of warmer temperatures needed to change the phase as shown in the below graph.
the totals of carbon contained in various reservoirs.
http://ethomas.web.wesleyan.edu/ees123/clathrate.htm 
