Geophys. Res. Lett. http://doi.org/ckbk (2018)

Warming of the Arctic and its permafrost regions will result in the release of carbon as soils thaw. Whilst estimates have been made of the greenhouse gas emissions from the permafrost thaw, other elements currently locked away will also be released, with implications for their global elemental cycles. One such example is mercury (Hg), which in certain forms can be highly toxic.

Credit: Steve Morgan/Alamy Stock Photo

To calculate the potential mercury inventory, Paul Schuster of the US Geological Survey, Boulder, Colorado and collaborators analysed 13 permafrost soil cores from a 500 km Alaskan north–south transect. Calculating the Hg-to-carbon ratio gave a median value of 1.6 ± 0.9 micrograms Hg per gram C. This ratio, along with known soil carbon maps, can be extrapolated to calculate that the Northern Hemisphere permafrost stores 1,656 ± 962 gigagrams Hg. This is double the amount found in all other sources combined.

This large store of Hg is currently locked away as the low temperatures prevent microbial activity from liberating it. However, warming and increased microbial activity could alter this, but currently the timescale and consequences for the environment and food webs are unknown.