Despite decades of global reductions in mercury emissions, mercury levels in Arctic wildlife continue to rise due to persistent mercury pollution. This trend poses serious ecological as well as human health concerns. New Danish research uncovers how ancient mercury pollution is transported via deep ocean currents, contributing to persistent contamination of Arctic ecosystems.
According to the study published in Nature Communications, “legacy mercury” from historical mercury pollution can remain active in ocean systems for a long time. It may persist for over 300 years after its release. Coal combustion and gold mining released vast amounts of mercury into the air. Much of it has now settled into the ocean. This mercury poses a long-term threat.
MERCURY ISOTOPES REVEAL OCEAN TRANSPORT PATHWAYS
Researchers examined more than 700 samples from polar bears, seals, fish, and environmental sources across Greenland. These samples were gathered over a 40-year monitoring period to study mercury pollution.
Scientists analyzed six types of mercury isotopes. They identified unique chemical fingerprints. These fingerprints help trace mercury’s origin and path through ocean currents. For example, areas of central West Greenland show mercury signals. These signals are tied to Atlantic waters entering via the Irminger Current. This is distinct from other Arctic regions.
ELEVATED MERCURY LEVELS IMPACT TOP PREDATORS AND HUMANS ALIKE
In top predators like polar bears and toothed whales, mercury levels are now significantly elevated due to ongoing mercury pollution. These levels are 20 to 30 times higher than before the industrial era began.
This neurotoxic metal impairs immune systems, damages reproductive health, and may disrupt sensory functions, which can reduce the survival rate of affected animals. Many Indigenous Arctic communities rely on these animals for sustenance. Therefore, human populations face elevated mercury exposure risks through their traditional diets.
EMISSIONS MAY BE DOWN, BUT LEGACY POLLUTION PERSISTS
The puzzle lies in the discrepancy: global mercury emissions have fallen since the 1970s, yet Arctic wildlife shows no parallel decline in contamination levels.
Researchers now believe that legacy mercury pollution, carried by slow-moving ocean currents from major emitters like China, explains this unsettling trend.
“Mercury that entered the oceans in the 1800s is still circulating.” Professor Rune Dietz, co-author of the study and longtime Arctic mercury researcher, made this statement, shedding light on the lasting impact of mercury pollution.
IMPLICATIONS FOR GLOBAL MERCURY POLICIES AND THE MINAMATA CONVENTION
This research challenges assumptions underlying international efforts such as the UN’s Minamata Convention, which aims to reduce mercury’s global impact.
Although emissions have dropped, the Arctic remains vulnerable due to delayed but ongoing mercury delivery via long-range ocean currents spanning up to 150 years. Policymakers must now consider ocean-borne mercury pollution as a persistent threat, requiring more robust long-term strategies to protect vulnerable wildlife and northern communities.
MERCURY’S LEGACY ISN’T OVER—IT’S STILL ARRIVING
The study makes it clear: even as we reduce mercury at the source, the Arctic is still receiving its toxic load—decades or centuries after release.
This finding emphasizes the importance of monitoring not just emissions, but also environmental reservoirs like oceans, which silently carry mercury pollution across generations.
