Abrupt stream acidification and metal mobilization linked to permafrost degradation

Elliott K Skierszkan , Andras J Szeitz, Matthew Lindsay , Sean Carey 

Stream chemistry and ecosystem function are being transformed by abrupt climate-driven acceleration of sulfide-mineral oxidation in permafrost-underlain headwater catchments of the Yukon and Mackenzie river basins—the two largest (sub)Arctic rivers in North America. Over the past decade, dozens of acidic (pH ~3) seepages have emerged in these headwaters, causing vegetation dieback and mobilizing metals at acutely toxic concentrations in receiving streams. Acid generated during sulfide-mineral oxidation also accelerates CO₂ emissions by driving carbonate-mineral dissolution. Major downstream sub(Arctic) rivers show significant multi-decadal sulfate concentration increases, yet their metals concentrations remain stable because of attenuation and dilution processes. Headwater stream acidification signals a major perturbation in metal, carbon, and sulfur cycling linked to permafrost thaw with far-reaching consequences for water resources, northern communities, ecosystem health, and Earth’s biogeochemical future.