Hi, Andrew - Thanks. Virtually all the clustered methane hotspots of ESAS are south of 76 degrees lat, & thus in the part of the Laptev that is all ~75ft or less in depth. That could still, normally, lead to almost total oxidation - but: what if the critters have as little health care & social security as we do!? No, seriously, boom & bust is par for the course in such microbial communities. And I was only talking about .4% getting out to the air, not a lot.
Above all, in the real world, it doesn't have to be - and really wouldn't at all be likely to be - all "new" methane, either. I was just using that as an example of how NO HYDRATES need to destabilize at all for there to be a very big problem there soon. In fact, all these "taliks" tend to be grouped around fault zones, where there's plenty of free gas to migrate up. Remember, additional to the 500Gt C that's been estimated to be in the permafrost and getting perforated, is possibly another 700Gt C as free gas, under the hydrates and pretty much spread all around this region. It's around the fault zones that the taliks can make very effective pathways for gas migration. So, maybe an even more realistic scenario than what I wrote before is actually: just .15% from submarine permafrost release, leading to a sudden gush of ~.2% of the free gas? As far as getting re-dissolved, I can't see why, once it's emitted, it would be any different than any other methane in the air. Yes, there's a small sink into soils of methane (~3% globally, I think), but don't know of any major oceanic sink (it's not listed at all in the IPCC methane budget I have sitting in front of me), although it wouldn't surprise me if there were a very small one, it would just surprise that it were at all significant. Cheers, Nathan On Mon, Apr 16, 2012 at 6:44 PM, Andrew Lockley <[email protected]>wrote: > Yes, but what's lost in the water column? Only very sudden releases > in shallow seas make it to the atmos, and much may re-dissolve as it > remains in the marine boundary layer. > > A > > On 16 April 2012 22:17, Nathan Currier <[email protected]> wrote: > > Going with what John Nissen just wrote earlier today on a different > > thread, it could possibly be very useful for policymaking, etc., and > > for those following this geoengineering group, to do something like > > the IPCC for future emission and mitigation scenarios, and construct a > > range of different 'Arctic event scenarios' for others to consider, > > involving methane, ice or both. > > > > For me, I personally find something like the following arctic methane > > scenario quite astonishing to contemplate, and please note that it > > neither goes against anything said recently by David Archer at Real > > Climate, nor posits any mechanism that is not currently already > > activated towards change, and is entirely based upon already observed > > flux rates, conditions, etc. > > > > Let’s imagine that just a small fraction of the only the NON-HYDRATE C > > around the ESAS permafrost were released as methane rather quickly, > > either in one season, or even episodically over two or three years. > > Let’s make it just a mere .45%. This would be equal to 3 Gt methane. > > (3Gt CH4 = 2.3 Gt C, and 2.3 Gt C = ~.45% of 500Gt C, the amount > > estimated to be around the ESAS submarine permafrost [Shakhova, > > 2010]). > > > > This is a quite credible scenario. It is certain that there are > > already releases coming from this source, and that there is currently > > significant deterioration of the state of this carbon store from > > influxes of warming waters, lost ice, etc. Current methane fluxes > > recorded in the water column from around these hotspots are >1000x > > those expected from the observed atmospheric anomolies, so > > considerable methanotrophic activity could already be activated, > > making irregularities of microbial consumption capable of such a > > release. An estimated 3-5% of ESAS submarine permafrost is currently > > covered with taliks and degraded [Shakhova, 2010], and extrapolation > > from current hotspot releases would actually equal ~3.5Gt/yr > > [Shakhova, 2010]. > > > > A pulse of 3 Gt CH4 doubles the methane increase since > > industrialization: we have increased methane by about +157% (700ppb + > > 1100ppb= ~1800ppb), with abundances being ~1.9Gt (pre-industrial) + > > 3Gt = 4.9Gt CH4 (current). With best understanding of all indirect > > effects, this 3 Gt has added ~1W/m2. Thus, this modest methane pulse > > would add quite quickly about +62% to all the increased radiative > > forcing since industrialization. > > > > Further, spreading it over a couple of years wouldn’t make all that > > much difference: the feedback effect for methane is a ~ -.2 loss rate > > for each +1% of methane emission rate, which holds for up to about 33% > > increase in emission rate. (After that, I believe the negative loss > > rate increases further – does anyone know what happens after this?). > > Roughly, the release would constitute a ~+500% change, so the pulse > > should, I believe, last for something like double the lifetime, or > > more, something like two decades or more. In any case, it would last > > long enough that I suspect it might cause Much Ado. > > > > -- > > You received this message because you are subscribed to the Google > Groups "geoengineering" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > [email protected]. > > For more options, visit this group at > http://groups.google.com/group/geoengineering?hl=en. > > > > > > -- > twitter @andrewjlockley > 07813979322 > andrewlockley.com > skype: andrewjlockley > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. 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