Antarctica’s retreating ice is exposing what scientists describe as a toxic threat, with the potential to contaminate one of Earth’s most untouched ecosystems.
A team from Peking University in Beijing has found that as the continent thaws, mercury locked away in ice for centuries is being released back into the environment in hazardous quantities.
The process is driving a “sharp increase” in poisonous mercury levels in sediments along the Antarctic coastline, according to the researchers.
They caution that the buildup could have “profound” effects on the fragile ecology of the polar region.
For the study, published in PNAS Environmental Sciences, the scientists examined sediment samples collected from 16 sites near the Antarctic Peninsula, the northwestern stretch of the continent.
Their analysis showed that mercury is now accumulating on the continental shelf at a rate of 93 micrograms per square metre each year.
Even in this remote part of the world, that figure means some Antarctic areas are taking in mercury at twice the rate recorded on other continental shelves.
Most concerning, the accumulation rate has climbed by 160 per cent since the beginning of industrialisation, a trend the researchers say points to the role of human-driven climate change.
Researchers from Peking University found that thawing ice in the Antarctic Peninsula (pictured) is releasing dangerous amounts of mercury that had been trapped for hundreds of years
Mercury is a heavy metal that is naturally present in low levels throughout the ecosystem.
Volcanoes and tectonic activity release mercury vapours into the atmosphere, from where they are gradually absorbed by tiny plants in the ocean called phytoplankton.
Some of these plants are eaten by fish, and the mercury builds up in the food chain, while others die and carry their trapped mercury to the bottom of the ocean.
Without human interference, this natural accumulation of mercury generally stays within safe rates so that levels entering the food chain don’t become toxic.
However, mercury is also released into the atmosphere in vast quantities by human activities such as burning coal and processing metals.
This has led to mercury levels increasing around the world, building up in the food chain to the point where it has become a health risk to animals and humans.
But the increase in atmospheric mercury alone isn’t enough to explain the staggering rates of accumulation around the Antarctic Peninsula.
Instead, the researchers found that the rapid melting of the continent’s ice shelf is to blame.
Retreating glaciers release mercury trapped in the ice and create more open water near the surface for mercury to enter the ocean from the atmosphere
As the planet warms and the ice shelf retreats, Antarctica is affected by two processes.
On one hand, the melting ice exposes more open water to the sun and air, giving phytoplankton more space to grow and suck mercury out of the air.
At the same time, the authors say that warming has ‘further promoted this enrichment by accelerating terrestrial input through ice melt, erosion and weathering’.
The Antarctic ice sheets have slowly absorbed mercury from the atmosphere over thousands of years, keeping these toxic minerals safely trapped.
Now, the melting ice is dumping vast quantities of previously trapped mercury into the ocean.
Since the start of industrialisation, the amount of mercury being released in meltwater has increased by 550 per cent.
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Meanwhile, the amount being absorbed from the atmosphere has also risen by 350 per cent.
The researchers say that these effects have been particularly pronounced around the Antarctic Peninsula because of how fast its ice is melting.
Since the start of industrialisation, rising temperatures (right) have accelerated ice melt (left) and triggered a 190 per cent increase in the rate of mercury accumulation around Antarctica
Studies have found that 62 per cent of Antarctica’s seabird species had levels of mercury in their body above the ‘no adverse health effect’
Despite making up less than 5 per cent of Antarctica’s total area, this small region contributes 60 per cent of the total mass lost from ice shelves in the last 30 years.
Today, nearly 90 per cent of all glaciers in the region are in retreat at a rate well above the limits of natural variation.
This stark warning comes as studies show that mercury is already beginning to build up in the Antarctic ecosystem.
Research conducted last year found that 62 per cent of Antarctic seabird species had levels of mercury in their body above the ‘no adverse health effect’ threshold.
More worryingly, a quarter of all species were found to be at moderate to high risk of mercury toxicity.
