Evaluation of mercury concentrations in Svalbard surface snow based on meteorological parameters

Over recent decades, Svalbard's climate has undergone significant transformation, driven by Arctic Amplification. Rising temperatures, retreating sea ice, and the intensification of extreme events have become increasingly prevalent. However, within this nearly consistent trend of warming, 2020 emerged as an anomaly, marked by unusually low temperatures, a strong polar vortex, and extensive sea ice coverage throughout the year. Two sampling campaigns were conducted during the snow season in Ny-Ålesund (Svalbard): one during a “warm” year (November 2018 to May 2019) and the other during a “cold” year (November 2019 to May 2020). These campaigns aimed to investigate the potential effects of the distinct climatic conditions of the “cold year” on the biogeochemical cycle of mercury (Hg) in surface snow. Mercury, a toxic element, has been extensively studied in polar regions. While many studies have sought to address changes in the Hg biogeochemical cycle under shifting climatic and atmospheric conditions, uncertainties remain—particularly regarding how variations in sea ice extent and duration may influence Hg deposition in the Svalbard archipelago and the Arctic as a whole. It is well known that sea ice releases reactive bromine species during spring, which can directly influence Hg deposition through atmospheric mercury depletion events (AMDEs) or, more broadly, by promoting Hg oxidation and deposition. Using the “warm” and “cold” years as case studies, we explored whether the significant increase in sea ice extent observed in the Kongsfjord during the cold year influenced Hg deposition. Although we observed an increase in ozone depletion events (which are primarily linked to bromine release from sea ice) during the cold year, we found no direct evidence of a corresponding increase in Hg content in snow. This suggests either that the sea ice increase during the cold year was insufficient to enhance Hg deposition through bromine emissions or that sea ice and its associated emissions do not play a primary role in controlling the Hg biogeochemical cycle.