Geoscience: Southwestern Greenland is a hotspot of mercury release

The southwestern margin of the Greenland Ice Sheet is a large source of mercury, with extremely high concentrations of dissolved mercury found in meltwater rivers flowing from its glacial catchments, according to a study published this week in Nature Geoscience. This source, which has not been accounted for in global mercury budgets, may have significant impacts on local and coastal ecosystems in the Arctic.

Mercury pollution is an issue of global concern due to the high toxicity of the element. High levels of mercury have previously been found in Arctic organisms. However, whether the Greenland Ice Sheet is a source of mercury and how significantly it affects downstream regions in the Arctic remain unknown. Such information is urgently needed, as the Greenland Ice Sheet is melting at an accelerated rate as the climate warms.

Jon Hawkings and colleagues measured mercury concentrations in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet during the summer melting season. The authors found that meltwater from southwestern Greenland exports significant amounts of mercury to downstream fjords. Export of dissolved mercury from this region is estimated to be globally significant — up to about 42 tons a year — equivalent to around 10% of the estimated global riverine export to the oceans. Concentrations of dissolved mercury in meltwaters were found to be among the highest recorded in natural waters. High concentrations of mercury also persist in downstream fjords, leading to potential risks of bioaccumulation in coastal food webs.

Further research is needed to understand mercury dynamics in ice sheet runoff across the entirety of Greenland, given the potentially elevated exposure of humans and ecosystems to this element.