Arctic mercury flux increased through the Last Glacial Termination with a warming climate

Mercury deposition onto the Greenland Ice Sheet increased from the Last Glacial Termination to early Holocene as the North Atlantic warmed and sea ice retreated, according to an ice-core mercury record and atmospheric chemistry modelling. Mercury is a pollutant of global concern, especially in the Arctic, where high levels are found in biota despite its remote location. 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 remains unknown. Here we present an Arctic mercury record covering the Last Glacial Termination to the early Holocene epoch (15.7-9.0 thousand years before 2000 ce), collected as part of the East Greenland Ice-Core Project. We find a threefold 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. Our results suggest that environmental changes associated with climate warming may contribute to increasing mercury levels in Arctic ecosystems.

Automated summary

According to ice-core data and atmospheric chemistry modeling, deposition of mercury onto the Greenland Ice Sheet increased during the transition from the Last Glacial Termination to the early Holocene epoch. This increase was associated with regional climate warming and the retreat of sea ice, driven by oceanic mercury evaporation and atmospheric bromine. The findings suggest that climate change may contribute to higher mercury levels in Arctic ecosystems.