This study reconstructs the Arctic mercury biogeochemical cycle during the Glacial-Holocene transition, revealing a three-fold increase in mercury levels in the early Holocene, which coincided with abrupt climate warming.

 Mercury is a pollutant of global concern, especially in the Arctic where higher levels are found in the biota compared to lower latitudes. Mercury is transported to the Arctic via atmospheric, oceanic, and riverine long-range pathways, where it accumulates in aquatic and terrestrial ecosystems. While present-day mercury deposition in the Arctic from natural and anthropogenic emissions is extensively studied, the control of past climate changes on natural mercury variability in the Arctic remains unknown. Here we present an Arctic mercury record covering the Last Glacial Termination to early Holocene (15.7- 9 thousand years before 2000 CE), collected as part of the East Greenland Ice-Core Project (EGRIP). We find a three-fold increase in mercury depositional fluxes from the Last Glacial Termination into the early Holocene, which coincided with abrupt regional climate warming. Atmospheric chemistry modelling, combined with available sea ice proxies, indicates that oceanic mercury evaporation and atmospheric bromine drove the increase in mercury flux during this climatic transition. In the context of current climate warming, progressive sea ice decline, and environmental change in the Arctic region, our results suggest a potential increase in oceanic Hg evasion in the near future. This study brings evidence that natural sources of mercury may contribute significantly to the Hg inventory in the Arctic in the coming decades.

Delia Segato, Alfonso Saiz-Lopez, Anoop S. Mahajan, Feiyue Wang, Juan P. Corella, Carlos A. Cuevas, Tobias Erhardt, Camille M. Jensen, Chantal Zeppenfeld, Helle A. Kjær, Clara Turetta, Warren R. L. Cairns, Carlo Barbante and Andrea Spolaor. Climate control on Arctic mercury variability during the Last Glacial Termination. Nature Geoscience. DOI: 10.1038/s41561-023-01172-9