Isn't that curious. Well here is the abstract.
However there is something fishy here and I'll explain later
The fishy thing is here, of the last author, Jeff Severinghaus. This is his publication list. And this one is the most interesting.
The idea is that temp changes change fractionation processes with heavy isotopes within the firn, causing an enrichment during the warming. Isotopes, that is, all the gas isotopes, isn't it? Seeing this abstract (anybody seen the complete study?) it does not appear that they corrected for this gravitational and molecular fractionation of the CH4 gas, did they?
If indeed they did not, then the corrected 'warming' isotope ratio should be a lot lower, right?
Here it is. http://static.mwnx.net/mac/Climatology/Ice record.pdf
Testing Just lost a post worth of an hour work.
Well here are the links
Bottom line was that Sowers and Schaefer et al see appear to see considerable differences in atmospheric oxidation and that the Clathrate methane source of the Preboreal, the Ormen Lange gas field was geologic methane not biogenic methane, with a different isotope signature.
It hasn't happend to me for a while because I put a lot of saftey procautions on my browser, but I used to save long posts on notepad so I would still have them and laugh in the face of my computer when my window closed or something.
Separate names with a comma.