Temperature trends in the sub-Arctic and Arctic have been notably on the rise in recent decades. In fact, in the last half century the overall annual mean Alaska temperatures have increased three to four degrees. As America’s only Arctic state, Alaska may be a proverbial canary in the coal mine for the rest of the United States when looking at the effects of climate variations. Such variations can affect water supplies, available flammable biomass fuels, or introduction of pests thus influencing crop harvests and local environments.
In the Alaska sub-Arctic and Arctic, tracking of these variations has shown a general increase in the number of frost-free soil days, a decrease in time periods with snow on the ground, an increase in precipitation and earlier river water exposures in the spring. Most concerning for many is the melting of permafrost (frozen soils maintaining their condition for 24 consecutive months or more). As thawing progresses, there is an increase in the emissions of previously locked up greenhouse gases so that organic materials locked up below the surface, without exposure to oxygen, are now free to decay with the diffusion of methane (and thus carbon).
The problem is that this becomes a self-perpetuating problem as the increase of methane in the atmosphere can then induce more warming. In fact, tundra areas have been referred to as a cyclic greenhouse gas “‘time bomb”’ when diffusion leads to more continual atmospheric heating, leading then to thawing and methane diffusion. Methane is a useful fossil fuel, yet there is no known effective way with such a broad diffusion range to capture it and port it to market for consumptive energy use, as there is with anaerobic digestion of small- scale livestock farm or landfill wastes).
The Geophysical Institute Permafrost Laboratory at the University of Alaska Fairbanks has mapped permafrost deposits in Alaska, and viewing it shows that roughly half of the State’s permafrost is continuous and permanent. Mapping by the United States Geological Service in 2016 demonstrates scattered subsurface uranium deposits throughout the state. Overlaying the two maps, there clearly are substantial deposits of uranium under permafrost, and uranium will decay under the frozen soils to produce the deadly and undetectable (to the human senses) health hazard of radon. As a uranium decay product and the heaviest noble gas, radon is hampered from diffusing and accumulates under ground ice and frozen soils. That is, until melting occurs.
While there hasn’t been empirical, applied research to quantify the diffusion of radon coming out through the active layer as permafrost melts, the concern over potential increases in radon comes from the fact that the United States Environmental Protection Agency lists radon as the second leading cause of lung cancer (only next to smoking). And while radon is an indoor air quality concern, the melting of soils will expand the area of viable building areas. Thus as previously marginal lands thaw and allow builders to put in basements or slab on grade foundations subsurface for residential homes, commercial buildings and schools, the danger of radioactive radon exposure to Arctic residents may become all the more acute. Canadian modeling from a dozen years ago has shown increased soil radon emanation caused by instantaneous and gradual permafrost thawing, yet this work was based on climate warming predictions which have been subsequently stepped up over the past decade since the estimates were created. The modeling demonstrated that permafrost reduces ambient radon concentration by 80 to 90%, and it was calculated that when frozen soils thawed the immediate effect would be 100 times the normal off gassing due to the sudden purging of accumulated radon reservoirs. (Note: It was assumed that these would become much lower in concentration once pent- up stocks were released and a steady rate of diffusion was released).
But radon gas isn’t the only hazard that is locked up in frozen Arctic soils and ice lenses, as there are considerable stores of methylmercury. Recent estimates from the United States Geological Survey reveal that Arctic permafrost is storing nearly twice as much mercury than in land, soil and air combined. According to research conducted north of the Arctic Circle in Alaska’s Brooks Mountains, almost three quarters of the mercury deposited in tundra soils comes from atmospheric drift of industrial nations’ emissions. Rather than contributing to indoor air problems with carcinogenic effects (such as radon avails), mercury diffusion can contaminate worldwide ecosystems by depositing the diffused mercury into food chains as well as Arctic runoff waters, which in turn can contribute to cardiovascular and neurological problems for the residents of many nations on a regional basis.
Based on field research at an experimental forest operated at the University of Alaska Fairbanks, it has been estimated that more than 15 million gallons of mercury is currently cached in permafrost, which is about 10 times the human- caused mercury releases in the last third of a century. With many circumpolar communities yet relying somewhat on hunting and gathering economies, immediate diffused methylmercury can threaten the already fragile food security in the Arctic.
While the Arctic may seem a far way from the vast majority of people, almost a quarter of the earth’s soils north of the equator happen to be permafrost. This abundant soil, whether continuous in tundra areas or discontinuous in sub-Arctic areas is the earth’s concentrated ‘frozen storehouse’ of methane, radon and mercury. There is certainly merit in investigating effects in the Arctic since thawing temperatures are on the rise overall, and do not seem to be abating any time soon.