Tap water no longer drinkable in Norwegian town as climate-related thawing releases heavy metals

Warning for other Arctic communities as residents told not to use water in Longyearbyen in Svalbard, one of the fastest-warming places in the world

Residents of a remote town in Norway that is in one of the fastest-warming places in the world have been told they must no longer drink tap water due to heavy metal contamination that scientists have linked to the thawing permafrost.

Longyearbyen, in the archipelago of Svalbard, gets its main drinking water supply from a 1.5 mile-long (2.5km) dammed lake called Isdammen, or "ice pond". Higher temperatures as a result of the climate crisis have thawed permafrost, leading to newly exposed bedrock leaching metals into the pond.

Longyearbyen, 800 miles from the north pole, is warming at between five and seven times the world's average rate, with autumn temperatures rising at up to 4C a decade.

Heavy metal contamination of the water supply is likely to be linked to two factors, researchers say: the thawing of permafrost - rock-hard ground that remains frozen all year apart from a so-called "active layer" that thaws in summer - and the geology of the former mining town.

"The combination of the thawing permafrost and the shale bedrock, which contains a mineral called pyrite, or fool's gold, is causing contamination of its water supply," said Marjolaine Verret, a permafrost expert and associate professor in Arctic geology at the University Centre in Svalbard.

When pyrite came into contact with water and oxygen, it oxidised and generated acidity, she explained. "The acid produced can now leach heavy metals from these rocks into the waterways. The issue we've been having here in Longyearbyen is manganese, but other contaminants can be leached out from the rocks."

The municipality, Longyearbyen lokalstyre, first alerted its 2,600 residents after manganese levels in the water supply were found to be 25 times higher than the 50 micrograms per litre recommended by the Norwegian Institute of Public Health, in September last year. The mayor of Longyearbyen, Terje Aunevik, said that while drinking water quality had never been good, due to sediment, the manganese levels had "gone ballistic".

Prolonged exposure to high levels of manganese can cause neurological problems, particularly in children and infants.

Emergency, temporary measures were rolled out, including the installation of a central tank of free purified water, filtered by the local brewery, for residents to refill containers at the local supermarket, and an investigation was launched.

Manganese levels have since dropped, but earlier this year sulphate and nickel levels were found to exceed recommended drinking water limits. As a result, the ban remains in place.

Aunevik said that while manganese levels were "not dangerous", government guidelines had to be followed. The drinking water crisis had created a lot of "noise", he admitted, with some residents angry at the inconvenience.

The mayor, who has commissioned an investigation into water quality, said a "completely new water mains supply" may be needed. Potential solutions being considered were installing a filtration system to Isdammen and having a desalination plant as a backup, or the other way around. Either way was "extremely expensive" and, due to the extreme temperatures of Svalbard, with water temperatures often below zero, would include technical challenges, Aunevik said.

"In Norway, where we have always taken for granted that we can drink the water from the tap, it is challenging to start thinking that we need to carry our water like we do now. Other small communities should be precautious and start thinking of what to do if it happens to their sources."

Verret and other scientists have warned that the contamination of water sources in Longyearbyen could be a foretaste of what is to come for Arctic communities.

"These ingredients [bedrock rich in pyrite and heavy metals] and thawing permafrost are present in other parts of the Arctic so this could be a first example of how climate change can impact freshwater, for example in northern Canada and Alaska," Verret said.