Mercury mobilization and export from the Greenland Ice Sheet using an ice-to-ocean approach

The Greenland Ice Sheet (GrIS) is a poorly constrained source of mercury (Hg) to Arctic ecosystems. We measured Hg concentrations and stable isotopes along an ice-to-ocean continuum to identify controls on GrIS Hg export. Early-season permafrost melt and rainfall produced high filtered total mercury (fTHg, ~17pM) and monomethylmercury (MMHg, ~2pM). As subglacial drainage evolved, particulate Hg doubled (from ~8 to 17pM) and MMHg production remained elevated, indicating Hg mobilization from subglacial environments. Shifts in Hg stable isotope ratios and Δ199Hg mass balance show supraglacial sources contribute 20–48% of exported Hg, suggesting subglacial inputs dominate the seasonal Hg flux. Fjord waters were enriched in fTHg (~10 pM) and MMHg (~2pM) relative to rivers, consistent with particulate Hg transformations and terrestrial Hg inputs. The estimated GrIS Hg yield (~23 mmol km−2 yr−1 ) is similar to that of Arctic rivers and will likely increase with climate-driven mass loss.