• Fri. Jun 18th, 2021

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Greenland’s ice sheet is releasing huge amounts of mercury into rivers

Greenland

The edge of the Russell glacier, which flows from the south-west of the Greenland ice sheet

Martin Zwick/REDA&CO/Universal Images Group via Getty Images

An ice sheet in the southwestern region of Greenland is releasing huge amounts of mercury into nearby rivers. The discovery is worrying as the toxic metal can accumulate in the marine animals that are a key dietary component for local Indigenous communities.

Mercury is a naturally occurring metal found in some rocks. As glaciers slowly flow downhill, they grind up the underlying rocks, potentially releasing mercury into their meltwater.

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To find out whether this is occurring in Greenland, Jon Hawkings at Florida State University and his colleagues analysed meltwater flowing from the southwestern margin of the Greenland ice sheet.

Hawkings and his team completed two expeditions to Greenland in 2015 and 2018, collecting water samples from three meltwater rivers that receive substantial amounts of water from the Greenland ice sheet – up to 800 cubic metres per second. The samples were filtered to remove any sediment and kept safe from contamination. Then the researchers analysed the mercury concentration in each one.

“[Mercury concentrations in this region] are at least 10 times higher than in an average river,” says Hawkings. This means the meltwater is as rich in mercury as some highly polluted rivers – except in this case the mercury hasn’t been introduced into the water directly by humans. “Although this mercury isn’t introduced by humans, the ice sheet is melting much faster as a result of climate change,” says Hawkings.

The researchers estimate this source of mercury is exporting significant amounts into downstream fjords – long, narrow bodies of water carved out by moving glaciers. This region in Greenland could be exporting up to 42 tonnes of mercury every year – around 10 per cent of the estimated global export of mercury from rivers into the oceans. The mercury concentrations are among the highest ever recorded in the scientific literature for natural waters not contaminated by human activity.

Mercury is one of the core elements of global concern because of its toxicity as it accumulates in food webs. “As you go further up the food chain, mercury becomes more concentrated,” says Hawkings.

This is especially concerning for members of the Indigenous communities living in the Arctic. “It is a region that contains both lots of melting glaciers and Indigenous communities that rely heavily on harvested marine animals from local waters as a food source,” says Maya Bhatia at the University of Alberta in Canada, who wasn’t involved in the study.

Journal reference: Nature Geoscience, DOI: 10.1038/s41561-021-00753-w

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