On Thu, 20 Dec 2001, Mike Lorrey wrote:
> But what evidence is there that this would happen? Hydrates are trapped
> not because of temperature, but because of pressure. Increasing pressure
> from melting glaciers raising ocean levels only makes hydrates more
> secure, not less. You would need to significantly lower ocean levels in
> order to trigger a hydrate release, something that only occurs during
> ice ages.
I would say they are trapped by both temperature and pressure.
See: "Methane Explosion Warmed the Prehistoric Earth, Possible Again"
They think it may have been triggered by continental plate movement.
But once it gets started it may runaway.
> This uplift of tectonic plates would have decreased pressure in the
> sea floor, and may have caused the large methane release. Once the
> atmosphere and oceans began to warm, Schmidt added, it is possible
> that more methane thawed and bubbled out. Some scientists speculate
> current global heating could eventually lead to a similar scenario in
> the future if the oceans warm substantially.
So it would appear that glacier/ice cap accumulation lessening oceanic
pressure might not be the trigger, but reduced continental surface area
and/or warming from other sources may be sufficient. An additional
possibility is changes in ocean currents causing warming of the ocean
bottom where hydrates have accumulated.
In the previous case the warming was 7 deg. C. That would result in
significant impact on humanity with quite possibly a large loss of life
due to weather pattern changes. Not something one wants to invite
on oneself unless one is sure one understands the problem fully.
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