Permafrost Thaw Looks Alien What You Need to Know
Hullo Archimid - it is your fault for making me think. At the end of that great video from USGS, there is a single reference to increased precipitation affecting permafrost / methane.
There has been a lot of stuff about increased snowfall in the freezing thread, some about the season to come from this winter's large snow fall and some looking further ahead, all saying that the increased snow on the ground will inhibit sea ice melt. i.e. -ve feedback. I am still not convinced.
I've been looking at another consequence of increased snowfall with potential significant longer-term impacts on AGW and therefore the potential for an ice-free Arctic. It seems increased snowfall may well accelerate breakdown of permafrost and release of methane and CO2. i.e. +ve feedback. Two examples below. (Also posted on ice-free arctic thread).
Example 1
https://www.sciencedaily.com/releases/2016/03/160302204625.htmHow permafrost thawing affects vegetation, carbon cycle
Study focuses on Toolik Lake area of Alaska's North Slope
Date: March 2, 2016
Source: University of Delaware
Summary:Scientists are exploring how the thawing of permafrost affects vegetation and the carbon cycle in the Toolik Lake area of Alaska's North Slope.
Climate models predict 25-50 percent more precipitation in the Arctic region by the end of the century, mostly as fall and winter snow. However, extra snow can also mean extra moisture during warmer seasons like spring and summer.
Snow fence experiment
During fieldwork, the scientists used an existing snow fence that had been in place for 18 years to explore what changes in average snow accumulation might mean for the Toolik Lake area.
Typical winter snowfall depth in the area is about one foot. The snow fence, which stands approximately 9 feet high by 200 feet long, was built perpendicular to the wind direction so that snowdrifts would form behind the fence. This allowed the researchers to mimic various snowfall accumulations for the region, from below normal to average to much higher levels of winter precipitation.
Snow blanket means longer growing season for plants
As they reviewed the data, the researchers discovered that in areas with increased winter precipitation, the ground didn't freeze as deeply because the snow acted like a blanket, keeping the ground warmer than normal.
Their findings showed that higher snow accumulations resulted in increased soil temperatures and a deeper thawing of the permafrost, which, in turn, resulted in increased microbial activity, increased melting depth and more water content in the soil that led to increased production of methane and more plant growth.
In areas with reduced snow accumulation, however, the soil acted as a methane sink because of enhanced activity of methane-oxidizing bacteria.
When the snow melted, scientists noted a longer growing season for plants and shrubs. In areas with higher snow, the soil also collapsed when the ice that was occupying the soil's pore space melted, causing depressions in the ground.
"It affected more than just the amount of methane produced, it changed the landscape and the types of plants that grew there. We started seeing woody plants -- dwarf trees like birch and other shrubs -- instead of just moss, lichens and grass."
Example 2
http://iopscience.iop.org/article/10.1088/1748-9326/11/9/091004/pdfAbstract
The dramatic shrinkage of Arctic sea ice is one of the starkest symptoms of global warming, with
potentially severe and far-reaching impacts on arctic marine and terrestrial ecology (Postet al 2013 Science 341 519–24) and northern hemisphere climate (Screen et al 2015 Environ. Res. Lett. 10 084006).
In their recent article, Alexeev et al (2016 Environ. Res. Lett. 11 074022) highlight another,
and unexpected, consequence of Arctic sea ice retreat: the thinning of lake ice in northern Alaska. This is attributed to early winter‘ocean effect’snowfall which insulates lake surfaces and inhibits the formation of deep lake ice. Lake ice thinning has important consequences for Arctic lake hydrology, biology and permafrost degradation......
....they show that impacts from an open Arctic Ocean in autumn are both direct, through
increased air temperature and precipitation, and indirect, through inhibiting bedfast ice formation in lakes leading to localised permafrost degradation and talik formation
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