Mercury Currents

Mercury Pollution Is Creeping into the Arctic via Ocean Currents — and Wildlife Is Paying the Price

Despite global efforts to curb mercury emissions, mercury pollution in the Arctic continues to rise — and a groundbreaking new study reveals why. Mercury already present in the ocean is traveling north on slow-moving currents, silently accumulating in Arctic ecosystems and wildlife.

Researchers from Aarhus University and the University of Copenhagen have traced this toxic journey using advanced isotope analysis, uncovering how legacy mercury from past industrial activity is still wreaking havoc in one of the world’s most remote and vulnerable regions.

Legacy Mercury Rides Ocean Currents to the Arctic

When mercury is released into the atmosphere — often from coal combustion, industrial processes, and gold mining — it can travel long distances before settling into oceans. Once in seawater, it doesn’t just disappear; it can remain for up to 300 years, circulating within global ocean currents.

The study, published in Nature Communications, analyzed over 700 biological and environmental samples collected across Greenland, including tissues from polar bears, seals, fish, and peat cores — some dating back 40 years.

“Mercury isotopes act like fingerprints, helping us track where the contamination comes from and how it moves,” explained lead author Jens Søndergaard, a senior researcher at Aarhus University.

Ocean Currents Determine Mercury Levels in Arctic Wildlife

The researchers found that different regions of Greenland are affected by distinct ocean currents:

• Central West Greenland is influenced by the Irminger Current of the North Atlantic, which carries less mercury but shows a specific isotope pattern (notably high in the heavy isotope δ202Hg).

• Northern and Eastern Greenland are impacted by currents flowing from the Arctic Ocean, which deliver higher mercury concentrations and older isotopic signatures — clear evidence of long-term accumulation.

These differences explain why animals in some Arctic areas show alarmingly high levels of mercury, even as global emissions have declined.

Why Mercury Levels Keep Rising in Arctic Predators

Despite international regulations and a drop in new mercury emissions since the 1970s, Arctic wildlife is not seeing relief. In fact, mercury concentrations in polar bears and toothed whales are now 20 to 30 times higher than pre-industrial levels.

“We’ve tracked mercury in Arctic species for over four decades. The global reductions haven’t translated into local declines,” said senior author Rune Dietz, an ecologist at Aarhus.

That’s because much of the mercury now entering the Arctic isn’t new — it’s legacy pollution, released during the industrial age and slowly drifting north via deep-sea currents.

Isotope Fingerprints Reveal Mercury’s Path

By analyzing the distinct mix of mercury isotopes in animal tissues, peat layers, and other samples, the team could map mercury’s journey across ocean basins. Isotopes found in modern surface layers of peat were heavier than those in deeper, older layers — clear evidence that recent pollution is still accumulating in the Arctic.

The isotope data provide a powerful tool for predicting where mercury will appear next, potentially offering early warnings before contamination spikes in vulnerable ecosystems.

Health Risks for Arctic Wildlife and Indigenous Communities

Mercury is a neurotoxin that can impair immune function, reproduction, and sensory perception in animals. In the Arctic, seals, polar bears, and seabirds are already showing signs of mercury-linked health problems, such as suppressed immunity and hormonal imbalances.

This toxic threat also impacts Indigenous communities that rely on marine mammals for food. The bioaccumulation of mercury in top predators means that traditional diets can carry health risks, especially for pregnant women and children.

“Once mercury is in the ocean, it enters a global conveyor belt — and removing it becomes nearly impossible,” said co-author Christian Sonne, a professor at Aarhus.

Why Mercury Pollution Is Hard to Reverse

The Minamata Convention on Mercury, adopted by over 130 countries, aims to reduce global mercury emissions. But the Arctic remains a troubling exception. This study explains why:

• Ocean mercury stores from the 19th and 20th centuries are vast and persistent.

• Currents can take up to 150 years to transport this pollution from source regions to the Arctic.

• As a result, Arctic mercury levels lag behind current emission trends and may remain elevated for decades — or even centuries.

What Can Be Done to Mitigate Arctic Mercury Pollution?

Although stopping legacy mercury is not feasible, there are key strategies to minimize future harm:

• Continue reducing modern mercury emissions to avoid adding to the ocean reservoir.

• Expand long-term monitoring programs to track isotope signatures and identify future hotspots.

• Issue dietary guidelines for Arctic communities to reduce health risks from contaminated food.

• Study climate change impacts, as warming temperatures and shifting currents could accelerate mercury transport.

Programs like GreenPaths and WhaleAdapt are helping researchers connect the dots across peat cores, glaciers, rivers, and Arctic food webs to forecast future contamination zones.

A Warning for the Future

The message is clear: mercury pollution is not just a past problem — it’s a continuing threat. Even with reduced emissions, the toxic legacy of the industrial era continues to harm Arctic ecosystems and communities.

As isotope tracking becomes more precise, scientists hope to predict and prevent future impacts. But meaningful progress will require global cooperation, long-term commitment, and support for those most at risk.