Joanmarie Del Vecchio , Marisa C Palucis, Colin R. Meyer

Amplified warming of high latitudes and rapid thaw of frozen ground threatens permafrost carbon stocks. The presence of permafrost modulates water infiltration and flow, as well as sediment transport, on soil-mantled slopes, influencing the balance of advective fluvial processes to diffusive processes on hillslopes in ways that are different from temperate settings. These processes that shape permafrost landscapes also impact the carbon stored on soil-mantled hillslopes via temperature, saturation, slope stability such that carbon stocks and landscape morphometry should be closely linked. We studied ~67,000 headwater basins between 25-90 °N to determine whether the thermal state of the soil sets the balance between hillslope and fluvial erosion processes, as evidenced by the density of the channel networks (i.e. drainage density) and the proportion of convex to concave topography (hillslopes and river valleys, respectively). Watersheds within permafrost regions have lower drainage densities than regions without permafrost, regardless of watershed glacial history, mean annual precipitation and relief. Independent of the dataset resolution and analysis method, we find evidence that advective fluvial processes are inhibited in permafrost landscapes compared to their temperate counterparts. Frozen soils likely inhibit channel development, and we predict that climate warming will lower incision thresholds to promote growth of the channel network in permafrost landscapes. By demonstrating how the balance of advective versus diffusive processes might shift with future warming, we gain insight into the mechanisms that shift these landscapes from sequestering to exporting carbon.