Impacts of Permafrost Disturbance on DOC, Total Dissolved Solids and Suspended Sediment in Low Arctic Coastal Catchments

Arctic climate change leads to permafrost degradation and to associated changes in freshwater quality. There is a limited understanding how disturbances impact water biogeochemistry on a catchment scale. In this study, we investigated concentrations and fluxes of dissolved organic carbon (DOC), total dissolved solids (TDS), suspended sediment (SS) and water stable isotopes in paired and adjacent Low Arctic watersheds that have been subject to permafrost slope disturbance. We combined data on permafrost disturbance between 1952 and 2015 with data on geochemistry along longitudinal stream profiles.

Our results show a decrease in total disturbed area by 41 % between 1952 and 2015, whereas the total number of disturbances increased by 66 % for the six studied watersheds. The spatial variability of hydrochemical parameters is connected to catchment properties, which are not necessarily reflected at the outflow. Degrading ice wedge polygons were found to increase DOC concentrations in one headwater stream, whereas hydrologically-connected disturbances were linked to increases in TDS and SS downstream. Although hydrochemical concentrations varied considerably in the paired watersheds, we found a linear relationship between catchment size and daily DOC and TDS fluxes for all six streams. Suspended sediment flux did not show a clear relationship as a hydrologically connected retrogressive thaw slump impacted the overall flux in one of the streams. Overall, water composition in this Low Arctic landscape is influenced by permafrost degradation and understanding the spatial variability will help to model the geochemical fluxes from Arctic catchments.