Large amounts of mercury could soon be released from frozen ground that will thaw as the Arctic warms.
When long-frozen ground called permafrost starts to thaw, this sometimes triggers the collapse of sloping land above bodies of water. The resulting landslide-like features, or ‘thaw slumps’, can release large amounts of sediment into waterways.
Kyra St. Pierre at the University of Alberta in Edmonton, Canada, and her team determined mercury concentrations in waterways close to thaw slumps in Canada’s Northwest Territories. Mercury levels downstream of the slumps were up to two orders of magnitude higher than upstream levels, reaching the highest concentrations ever measured in otherwise uncontaminated sites in Arctic Canada.
The team estimates that across the Arctic region, climate warming and the resulting expansion of thaw slumps could spark the release of almost 90,000 tonnes of mercury — 5% of all mercury currently stored in northern permafrost soils.