The Arctic contains vast amounts of mercury trapped in permafrost. As temperatures rise, the mercury is being released injury the apex predators of the region. A paper in Geophysical Research Letters alerts us the scale of the problem could be staggering.
Greenhouse gasses are inducing faster warming in the Arctic than elsewhere, melting vast quantities of permafrost, both on the tundra and the seabed. The great defrost is liberating whatever has been stored in the ice. So far increased attention has focused on the great debate as to whether the abundant methane liberated been able to reach the atmosphere, accelerating warming still further, but there is more to worry about.
There is an average of 43 nanograms of mercury per gram of soil at 13 websites across northern Alaska, a team led by Dr Paul Schuster of the US Geological Survey, discovered use soil cores. This is one 600,000 th of the carbon people are justifiably worried about. Regrettably, mercury is dangerous in far smaller quantities than carbon dioxide or even methane.
Extrapolating based on what we know of soils in the rest of the Arctic, the authors estimate there are almost 800,000 tonnes( 900,000 tons) of mercury frozen in the permafrost( plus or minus more than half that ). A similar amount is held in non-permafrost clays in the same regions. This is much higher than previous approximations and is “more than twice just as much mercury as the rest of all soils, the ambiance and ocean combined.” The figure is so high because mercury deposited at these latitudes get stored there for an estimated 14,000 years, while in other locations it is rapidly recycled.
Studies over the last decade have revealed that some of this mercury is being liberated as permafrost thaw, and the Arctic Ocean is feeding mercury into the Atlantic and Pacific, but calculating the scale of assessments of the problem is a different matter. The situation is complicated by the fact that forest fires likewise liberate mercury, and reactions with ozone accelerate deposition during periods of high atmospheric mixing.
Nevertheless, the consistency of their measurings across permafrost regions has stimulated Schuster and co-authors confident they’re in the right ballpark on the sums waiting to be released.
How fast this mercury will escape into the wider biosphere depends on how quickly the permafrost meltings, which in turn depends mainly on specific actions we take to address emissions of greenhouse gasses.
The paper says the freeing of much of this mercury over the next century- which will occur if emissions are not curtailed- will have “unknown outcomes to the environment.” Nonetheless, mercury bioaccumulates in the food chain, and can destroy the minds of animals, including humen, so it’s unlikely those outcomes will be good.