Toxic mercury discharged from melting glacier

Water melting off the Greenland Ice Sheet is releasing high levels of mercury, new research reveals.

According to a recent report, the concentrations of dissolved mercury detected in water melting from the glacier are among the highest recorded in natural waters and equal contaminated rivers in industrial areas of China.

An international team of researchers sampled water from three seemingly pristine glaciers on the southwestern margin of the Greenland Ice Sheet, and two fjords the meltwaters flow into.

“The mercury concentration on the surface of the ice where a lot of the meltwater is coming from is very low, but the concentrations in the rivers that are coming out of the ice or from beneath the ice was very high,” notes Jon Hawkings from Florida State University, lead author of the study published in the journal Nature Geoscience.

The researchers believe that, as the glaciers move seawards, they act as "natural bulldozers", crushing the underlying mercury-rich bedrock and releasing the toxic metal. This mercury then flows into the ocean in the meltwater.

While it is unclear whether the mercury is making its way into the marine food chain, Hawkings stresses that seafood from the waters surrounding Greenland is regarded as safe to eat. “I would never have any concerns about eating any of the produce that comes out of Greenland.”

He further states that, “there is no evidence - yet - to suggest that these high concentrations are an issue for that seafood.” 

Nevertheless, with glaciers covering about 10 per cent of the planet, the impact of global warming means that this is an open question.

"It is going to be very difficult to manage in the future, because you can’t turn off a glacial meltwater river – you can’t just turn a tap and reduce the amount of water getting into the ocean," Hawkings points out.