The Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km⁻² year⁻¹) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km⁻² year⁻¹). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year⁻¹), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year⁻¹). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming.

格陵兰冰盖目前并未计入北极汞预算，尽管每年流入海洋的径流大量且不断增加，以及北极生物体内汞含量高的社会经济问题。在这里，我们展示了格陵兰冰盖西南边缘三个冰川集水区融水中的汞浓度，并根据夏季消融季节收集的样本评估了汞出口到下游峡湾的情况。我们表明，溶解的汞浓度是天然水域中记录的最高浓度，这些冰川集水区的汞产量（521-3,300 mmol km ^-2年^-1）比北极河流（4-20 mmol km）高两个数量级^-2年^-1）。据估计，来自格陵兰西南地区的溶解汞通量具有全球意义（15.4-212 kmol 年^-1），约占全球河流通量的 10%，包括生物蓄积性甲基汞的出口（0.31-1.97 kmol 年）^-1）。发现高溶解汞浓度（~20 pM 无机汞和~2 pM 甲基汞）在峡湾的盐度梯度中持续存在。平均颗粒汞浓度是文献中记录的最高浓度（约 51,000 pM），径流中溶解的汞浓度超过了报告的地表冰雪值。这些结果表明冰盖床的汞的地质来源。高浓度的汞及其对下游峡湾的大量出口对北极生态系统具有重要意义，突出了迫切需要更好地了解全球变暖下冰盖径流中汞的动态。