A new study has shown that the melting of Antarctica is returning to the sea mercury that had been accumulated in the ice for approximately two centuries. This discovery raises significant concerns about the potential effects on marine ecosystems.
The findings, published in the Proceedings of the National Academy of Sciences (PNAS), suggest that global warming has the potential to turn the icy continent into a new source of environmental pollution. Although mercury is naturally released by volcanic activity and rock erosion, the burning of fossil fuels and the increase in mining since the Industrial Revolution have drastically raised the concentration of this metal in the environment.
For many decades, Antarctica served as a vast natural reservoir, retaining mercury in its ice layers, which helped reduce the amount of contaminant reaching the oceanic food chain.
The research, led by environmental scientist Chengzhen Zhou from Peking University, focused on analyzing sediment cores taken from the Antarctic Peninsula, an area characterized by the fastest melting of the continent. The researchers found that the local continental shelf accumulates mercury at twice the global average rate, with this accumulation growing by about 160% since the beginning of industrialization.
In addition to the already known atmosphere-ocean cycle, the study identified a second mechanism intensified by climate warming: the atmosphere-glacial-land-ocean cycle. This cycle is responsible for reintroducing mercury that remained trapped in the ice for decades.
According to the researchers, this process causes the contaminant stored on the continent to be remobilized. Chengzhen Zhou and his team state that 'the coupling of these two cycles increased the release of terrestrial mercury driven by ice melt by 550% and the exchanges between the atmosphere and the ocean by 350%.'
Among the most important results of the study is the fact that the World Health Organization classifies mercury among the ten chemicals most concerning to public health, even when present in low concentrations.
Additionally, the study recalls previous discoveries pointing to the existence of bacteria in Antarctic sea ice capable of converting mercury into methylmercury, a substance much more toxic that bioaccumulates in marine life.
The authors warn that 'the accelerated enrichment and circulation of mercury in Antarctica may increase risks to Antarctic ecosystems.' They emphasize that the Southern Ocean food chain, ranging from diatoms to krill, fish, and large predators, is particularly vulnerable to methylmercury.
The researchers also noted that the export of mercury from the Antarctic Peninsula to the open ocean increased by about 400%, suggesting that contamination may reach other areas. The study concludes that reducing emissions from burning fossil fuels remains one of the primary strategies to control this environmental problem.
