Is there a way to date the hydrates and if so has it been done?
If Arctic hydrates are exclusively younger than Eemian times it indicates that whatever clathrates had formed earlier have outgassed during the Eemian & will do so again as we reach for Eemian temperatures. Since we're heating things up much more rapidly than ever before it seems as though what could have been a measured release in the past might accelerate and cause a feedback allowing the 20 year effects of CH4 to cause ever more rapid outgassing.
I'm not sure about dating them - if there is any isotopic signature or similar that could do the trick. However - it seems possible to infer for some locations at least whether or not the activity is brand new or has been ongoing at at least some level for a long time:
http://www.sciencedaily.com/releases/2012/09/120924144054.htmIf there are the associated carbonate deposits, that seems to provide an indication of the length of activity - and so does the presence of hydrogen sulphide within the water, given that this states the growth of bacterial colonies to be rather slow in this environment (makes sense if you look at just how low the solubility of methane in water is and the low temperatures - around 40mg/l if memory serves)
I haven't seen anything commenting on the presence of either indicator on the ESAS sites to date. It wouldn't rule out a significant increase in activity, but it would help identify if at least some level of activity had been ongoing for a long time (as off Svalbard in deeper water).
I'd like to think it ought to be possible to refine the results of the Svalbard expedition to try to infer recent history in terms of changing release of methane with more data, ie if hydrogen sulphide concentration is low vs methane, it would indicate a recent increase in methane release (I can see this would have limited value in regions where the water is saturated with either gas).
My understanding is that the clathrate deposits on the ESAS are up to 200m thick (substantially thicker than the typical water depth) - perhaps another way to approach the question of how old they might be is to try to come up with some estimate of how fast they are formed and grew to such thickness? Is 1cm every 5 years a likely rate of growth of such a deposit? (200m in 100,000 years - feels a bit faster to me but I really don't know)
I'm personally convinced that Shakhova and Semiletov were told at some point to keep quiet about the results of their 2011 cruise. Hope this doesn't require me to don the tinfoil chapeau.
Best wear it. After all, if you'd claimed certain western governments were spying on virtually every online means of communication and mass harvesting communications with automated algorithms and even in some cases storing total regional internet activity for limited durations - you'd have been told to wear it (pre Snowden).
Whatever the denier types and obsessive mainstreamers (and the two groups are rapidly moving closer together as far as I can see - mainstreamers being more vocal in opposing scenarios at the worse end of the spectrum and deniers gradually falling back on IPCC statements to try to defend their positions) think, I think keeping an open mind is really rather important in these matters. While nobody can rule a catastrophic near future release of methane probable - key experts in that area seem unable to rule it out or even to say they're confident it is very unlikely.
Hopefully Semiletov and Shakhova will release more papers soon - that seems to be the best place to look for what they have to say.
I think it should be kept in mind that we live on a planet that is capable of profound and rapid changes - a complex machine that we are nowhere near understanding.
One would think there would be lessons for the deniers and mainstream obsessives in just how fast the sea ice is changing versus expectations - but no - rinse and repeat, it seems.