Antarctica's melting ice is releasing dangerous quantities of mercury that have been trapped for hundreds of years, potentially poisoning the continent's ecosystem, scientists from Peking University have warned. The thawing ice is causing a sharp increase in the levels of the toxic metal found in sediments along the Antarctic coastline.
Researchers studying sediment samples from 16 locations near the Antarctic Peninsula discovered that mercury is accumulating on the continental shelf at a rate of 93 micrograms per square meter per year. This rate is double that of other continental shelves and has increased by 160% since the start of industrialization, suggesting a link to human-caused climate change.
Mercury, a heavy metal, is naturally present in low levels in the environment. It enters the atmosphere through volcanic activity and tectonic processes, where it is absorbed by marine phytoplankton. This mercury can build up in the food chain or sink to the ocean floor when organisms die. While natural accumulation typically remains within safe limits, human activities, such as burning coal and metal processing, have significantly increased atmospheric mercury levels globally.
However, the alarming accumulation rates around the Antarctic Peninsula cannot be solely explained by increased atmospheric mercury. The study indicates that the rapid melting of the continent's ice shelves is a primary driver. As global temperatures rise, melting ice exposes more open water, providing greater surface area for phytoplankton to absorb mercury from the atmosphere. The warming also accelerates terrestrial input through ice melt, erosion, and weathering.
Over millennia, Antarctic ice sheets have absorbed mercury from the atmosphere, trapping it safely. Now, the melting ice is releasing vast quantities of this previously sequestered mercury into the ocean. Since the onset of industrialization, mercury released in meltwater has increased by 550%, and atmospheric mercury absorption has risen by 350%. These effects are particularly pronounced in the Antarctic Peninsula due to its rapid ice melt.
This region accounts for 60% of the ice shelf mass lost from Antarctica in the last 30 years, despite comprising less than 5% of the continent's total area. Currently, nearly 90% of glaciers in the region are retreating at rates far exceeding natural variations.
The consequences are already becoming evident in the Antarctic ecosystem. Research published last year found that 62% of Antarctic seabird species had mercury levels exceeding the 'no adverse health effect' threshold. A quarter of these species are at moderate to high risk of mercury toxicity.