When picturing global pollution hotspots, the icy expanses of Antarctica rarely spring to mind. Miles away from major urban centres and heavy industry, this remote continent feels entirely insulated from human activity. Yet, beneath the freezing waters surrounding the Antarctic Peninsula, mercury is building up in seafloor sediments at an alarming pace.
Published on 27 July in the Proceedings of the National Academy of Sciences, a new study reveals a stark reality. Driven by a combination of rising industrial emissions and global heating, dangerous levels of this heavy metal are pouring into the Southern Ocean, posing a severe threat to local marine life.
As the study’s authors note, polar warming is fundamentally altering the landscape, turning Antarctica’s cryosphere from a mercury sink into an active secondary source of pollution.
From Sink to Source
Mercury is a potent neurotoxin capable of causing profound harm to both human health and delicate ecosystems. While natural phenomena account for some emissions, human activities—such as coal-fired power stations, waste incinerators, mining operations, and cement production—are the primary culprits. Industrial plumes travel hundreds of miles through the atmosphere before settling onto snow, ice, and open seas, eventually becoming locked away in ice sheets and seafloor sediment. Historically, both polar regions acted as global traps, or sinks, for this toxic metal. Now, that dynamic is breaking down.
To understand this shift, researchers looked back over the last two centuries in the Antarctic Peninsula, which stands out as the continent’s fastest-warming region with the most severe glacier melt. By analysing chemical and isotopic records extracted from 16 sediment cores along the continental shelf, and pairing them with a computer model, the team tracked how mercury has moved and accumulated over time.
Despite being worlds away from industrial smokestacks, the Antarctic Peninsula shelf now records a mercury accumulation rate that is twice the global average. Since the dawn of industrialisation, this rate has surged by 160%, elevating the region into a major hotspot for marine mercury enrichment.
The computer model pointed to two interconnected drivers behind this acceleration:
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Atmospheric Absorption: Greater atmospheric emissions mean more mercury is raining down onto the Southern Ocean. As sea ice retreats and open water spreads, the ocean absorbs even more of the pollutant from the air.
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Terrestrial Release: Melting glaciers and heavy erosion are flushing out mercury that has spent decades trapped within the Antarctic landmass and ice sheets.
Over the past two hundred years, the interaction between these two loops has driven a 550% increase in ice-melt-driven terrestrial mercury release and a 350% rise in air-sea exchange. Climate warming is effectively awakening a massive historical reservoir of mercury in Antarctica, turning it into an active secondary pollution source that heightens ecological risks across the polar south.
A Global Polar Problem
Antarctica is far from alone in this vulnerability. The Arctic is undergoing a remarkably similar transformation. A 2024 study uncovered heavily elevated mercury levels along riverbanks in Alaska, indicating that thawing permafrost is bleeding stored pollutants straight into northern waterways. While the total volume of mercury locked within Arctic permafrost remains uncertain, experts warn it could be immense.
As co-author Josh West of the University of Southern California previously noted, there could be a giant mercury bomb in the north waiting to break free as the climate warms.
As Earth’s polar regions flip from absorbing mercury to releasing it, the imperative to curb carbon emissions and industrial pollution grows increasingly urgent. The warmer the poles become, the more dangerous our chemical legacy will prove.
