In collaboration with other international partners, scientists from Ca’ Foscari University of Venice and the Institute of Polar Sciences of the National Research Council (Cnr-Isp) examined the relationship between past climate variations and Arctic mercury levels to understand how natural factors affect mercury biogeochemical cycling.
The East Greenland Ice Core Project (EastGRIP), coordinated by the Centre for Ice and Climate in Copenhagen, examined mercury dynamics between 9,000 and 16,000 years ago during the transition from the Last Glacial Period to the Holocene. Mercury levels during this transition were greatly impacted by sea ice decrease.
“Our study shows that mercury deposition in the Arctic tripled at the beginning of the Holocene compared to the Last Glacial Period,” says main author Delia Segato, a PhD student in Science and Management of Climate Change at Ca’ Foscari University of Venice.
“Thanks to the analysis and interpretation of paleoclimatic archives and the development of an atmospheric mercury chemistry model,” Segato says, “the study concluded that the loss of sea ice, especially the perennial one, in the subpolar Atlantic Ocean due to climate warming 11,700 years ago was the main cause of the increase of mercury deposition in the Arctic.”
Mercury, a global pollutant, is examined in Nature Geoscience by Italian researchers.
Internationally measured mercury emissions are not exclusively anthropogenic. Volcanic activity and many physical, chemical, and biological processes in the soil, ocean, and atmosphere affect the mercury biogeochemical cycle.
Andrea Spolaor, corresponding author and researcher at Venice’s Institute of Polar Sciences, says sea ice controls these processes in polar locations. Perennial sea ice, frequently several meters thick, prevents mercury from escaping the ocean to the atmosphere due to its volatility.
“On the contrary, seasonal sea ice, being thinner, more permeable, and more saline, allows mercury transfer and promotes complex atmospheric reactions involving bromine and increases the frequency of atmospheric mercury depletion events, causing more rapid deposition in the Arctic environment,” says Spolaor.
Since satellite monitoring began in the 1970s, Arctic perennial sea ice has declined by over 50% due to global change. Future research will evaluate how this event may affect mercury levels and the consequences to Arctic communities and ecosystems.”