Stream acidification and metal mobilization linked to permafrost degradation

We document rapid, climate-driven intensification 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, acidic (pH ~3) seepages have appeared in these headwaters that mobilize metals at acutely toxic concentrations and degrade water quality and chemistry in receiving waterbodies. These headwater processes drive multi-decadal increases in sulfate concentrations in major downstream (sub)Arctic rivers (Ogilvie, Klondike, Peel). This major perturbation in mineral weathering linked to permafrost thaw is an emergent climate–geosphere feedback with far-reaching consequences water resources, ecosystem health, and Earth’s biogeochemical future.