Permafrost Landscape History Shapes Fluvial Chemistry, Ecosystem Carbon Balance, and Potential Trajectories of Future Change

Intensifying permafrost thaw alters carbon cycling by mobilizing large amounts of terrestrial substrate into aquatic ecosystems. Yet, few studies have measured fluxes and constrained drivers ecosystem balance across heterogeneous Arctic landscapes. Here, we characterized hydrochemical landscape controls on fluvial cycling, quantified fluxes, estimated contributions to 33 watersheds in four ecoregions the continuous zone western Canadian Arctic: unglaciated uplands, ice-rich moraine, organic-rich lowlands till plains. Major ions, stable isotopes, speciation revealed patterns defined terrain relief accumulation organics. In previously mountainous watersheds, bicarbonate dominated export (70% total) due chemical weathering bedrock. lowland where soil organic stores were largest, lateral transport dissolved (50%) efflux biotic CO2 (25%) dominated. affected thaw-induced mass wasting, erosion tills enhanced increased particulate two orders magnitude. From an perspective, not wasting was, average, equivalent 6–16% net exchange (NEE). approached 60% NEE. Because future intensification thermokarst activity will amplify export, determining fate diverse northern landscapes is a priority for constraining trajectories region balance.