Melting Antarctic Ice Could Release More Mercury Into the Southern Ocean, Study Finds
A new study finds Antarctic glacier melt may be increasing mercury release into the Southern Ocean, raising concerns over toxic methylmercury, marine food chains and the impact of climate change on legacy pollution.
Antarctica, long regarded as one of the most remote and pristine regions on Earth, may be releasing increasing amounts of mercury into the Southern Ocean as climate change accelerates ice melt, according to new research examining the continent’s changing mercury cycle.
For decades, Antarctica’s extremely cold environment has acted as a vast reservoir for pollutants transported from other parts of the world. Atmospheric and oceanic circulation can carry contaminants, including mercury, over long distances before they are deposited and stored in ice, snow, soils and marine sediments.
But as global temperatures rise and Antarctic ice continues to retreat, some of these historically stored contaminants may be mobilized again and released into surrounding waters.
The findings raise concerns about how climate change could reshape the global movement of mercury a toxic heavy metal capable of accumulating in marine ecosystems and ultimately entering the human food chain.
Mercury Accumulation Has Increased Since the Industrial Era
Researchers from Peking University collected and analyzed 16 sediment samples from the continental shelf around the Antarctic Peninsula, one of the regions experiencing particularly rapid environmental change.
Chemical analysis indicated that the average rate of mercury accumulation in sediments had increased by approximately 160% since the beginning of the industrial era, with a particularly noticeable acceleration occurring from around the 1950s onward.
The findings suggest that both historical human generated mercury emissions and changes in the Antarctic environment are influencing the amount of mercury being deposited and redistributed across the region.
Mercury released elsewhere in the world including from activities such as coal combustion and mining can travel long distances through the atmosphere before eventually reaching polar environments.
Once deposited, mercury can remain stored in snow, ice, soils and marine environments for extended periods.
Climate change, however, is altering this process.
Glacier Melt Could Be Increasing Mercury Release Into the Ocean
Researchers used computer models to examine the global mercury cycle and estimate how different sources contribute to mercury found in Antarctic marine sediments.
Their analysis suggested that mercury released from glaciers into the ocean has increased by as much as 550% since the beginning of the industrial era.
The researchers estimated that approximately 56% of the mercury detected in marine sediments around the Antarctic Peninsula originated directly from atmospheric deposition.
The remainder was likely associated with processes including glacial meltwater, weathering and the erosion of ice, soils and sediments on the continent.
As temperatures rise, melting glaciers and increasing erosion can mobilize contaminants that have remained trapped for decades or longer.
Changes in interactions between the atmosphere, ocean, ice and land may therefore accelerate the movement of mercury through the Antarctic environment.
Climate Change Could Reshape the Global Mercury Cycle
The findings illustrate an important but sometimes overlooked consequence of climate change: warming can affect not only temperatures, sea levels and ecosystems, but also the movement of pollutants.
Mercury emitted by human activities can circulate globally before reaching remote environments.
Historically, polar ice and frozen soils have acted as reservoirs capable of storing some of this contamination. As these frozen environments change, previously deposited mercury may be remobilized.
This creates what scientists sometimes describe as a legacy pollution problem even if current emissions are reduced, contaminants released decades ago can continue circulating through the environment.
Researchers say climate change could therefore make controlling global mercury pollution more complicated than simply reducing present-day emissions.
Toxic Methylmercury Can Enter the Marine Food Chain
One of the greatest concerns arises when mercury in the environment is transformed into methylmercury, a highly toxic organic form of the metal.
Certain microorganisms can convert mercury into methylmercury under suitable environmental conditions.
Once formed, methylmercury can be absorbed by small marine organisms and progressively accumulate through the food web a process known as bioaccumulation and biomagnification.
The contamination can move from microorganisms and plankton to krill and fish, and eventually into seabirds and marine mammals.
Humans can also be exposed to methylmercury, primarily through the consumption of contaminated seafood.
Previous research has shown that microorganisms associated with Antarctic marine environments are capable of contributing to mercury transformation, highlighting the potential for mercury released into the Southern Ocean to become biologically available.
Mercury Exposure Can Damage the Nervous System
Methylmercury is particularly concerning because of its effects on the nervous system.
At sufficiently high exposure levels, it can interfere with neurological function, development, behavior and reproduction in wildlife.
The issue is also relevant to human health. Mercury is recognized by the World Health Organization (WHO) as one of the chemicals of major public health concern.
Exposure to mercury can affect the nervous, digestive and immune systems, while certain forms can also damage the lungs, kidneys, skin and eyes. Fetuses and young children are particularly vulnerable to the neurological effects of methylmercury exposure.
Similar Changes Are Emerging in Other Cold Regions
The phenomenon is not limited to Antarctica.
Scientists have observed comparable processes in other cold regions, particularly the Arctic, where thawing permafrost can release mercury and other contaminants that have remained trapped in frozen soils.
Environmental changes elsewhere may also alter the movement of pollutants.
In the northeastern United States, for example, increasingly intense storms and erosion can influence how mercury and other contaminants are transported through watersheds and ecosystems.
Together, these observations suggest that climate change may be reshaping the mercury cycle across multiple regions of the world.
Cutting Emissions Remains Important But Legacy Mercury Could Persist
The findings present a long-term challenge for global efforts to reduce mercury pollution.
Reducing new emissions from sources such as coal combustion, mining and industrial activities remains an important strategy for limiting future contamination.
However, mercury already deposited in glaciers, frozen soils and other environmental reservoirs represents a legacy of historical pollution.
As global warming continues to melt ice and alter frozen environments, some of this stored mercury could continue to be released into oceans and ecosystems even if new human-generated emissions decline.
This means improvements in environmental mercury levels may not occur immediately following reductions in current emissions.
The Antarctic findings therefore highlight a broader connection between climate change, environmental pollution, marine ecosystems and human health.
As the planet warms, scientists are increasingly examining not only what is being lost from the world’s frozen regions, but also what long-stored substances could be released back into the environment.
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