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Author Topic: melting permafrost as a (hidden) heat sink for "missing warming"?  (Read 1996 times)


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 Searching "permafrost changes" at this and other climate sites pulls many references to carbon flux as methane release, but very little discussion about the thermodynamics of land-based subsurface ice interacting with increasing solar energy retained by greenhouse effects.

 I was an arctic ecologist (in a past lifetime 40+ years ago) studying plant populations that segregated in part by height above the water table, available nutrients, etc. My favorite project used aerial photos to define micro-topography by color of plant communities.
The arctic plain across the mainland and most islands is soggy bog, mostly flat from shoreline to miles inland, with an "active layer" that freezes and thaws in turn each year (the energy flux cycles 80 calories or 336 joules per gram water at change of state - plus 4.2J/gm for each degree change in temperature before and after the state change). The active layer is underlain by permanently frozen wet ground that is typically well below 0C (again, 4.2J/gm per degree change). The numbers relate to the water component, with soil type and density as additional variables.

 Energy added to this system raises the baseline temp of the frozen ground, applying 4200J/KG per degree change, and 336KJ/KG at freeze/thaw state change. Flux change after permafrost melt essentially stores energy as a heat sink when smaller amounts of wet soil refreeze, and the midwinter temp minima increase.

 As permafrost decreases in volume, the active layer increases, with shifts in annual flux that vary by refreeze depth and mid-winter minimal temps.
 Water in the active layer is mobile, leaching into creeks and rivers to reach the ocean. In addition to the energy flux dynamics mentioned above, adding heat to this system results in larger amounts of free fresh water, with increased amounts making it to the sea. We talked a lot about that stuff at the time, but the climate was relatively stable, and the annual variability did not seem to be a large issue, beyond local effects on plant communities through released nutrients, surface water temp, etc. Methane seeps had interesting effect on some plant types, and were fun if you could light one afire, but no one cared else.

 I've already used more numbers than I should (is why I do neuroscience - necessary math is limited, and easily passed off to others), so by definition we're in qualitative territory, but seems to me this component of the annual arctic energy budget has gotten too little attention.

 If this topic is finding interest these days, I'd appreciate a link or two to get me there. This may well be another in the "real, but low impact" category. If I am overvaluing the significance, feel free to let me know.


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Re: melting permafrost as a (hidden) heat sink for "missing warming"?
« Reply #1 on: December 05, 2014, 08:23:13 PM »
That's a very scary thought, PJ!

BTW, welcome to the forum  8)