Understanding water flowpaths and origins in an Arctic Alaskan basin: Implications for permafrost hydrology under global warming

Global warming is progressing more rapidly in the Arctic compared with other regions of the world, and the increasing temperature has caused gradual permafrost thaw, resulting in significant changes in hydrological processes. However, the quantitative contributions of different water sources to Arctic watersheds under ongoing climate change remain poorly understood. Therefore, this study aims to address this gap by applying a water isotope-based mixing model to better quantify the sources and pathways of water flow in permafrost-affected catchments. In this study, isotopic and chemical data were used to determine the water sources and flowpaths of the Sagavanirktok (Sag) River on the North Slope in Alaska (USA) in the summer of 2022. Results obtained using a Bayesian mixing model indicate that meltwater from permafrost ice wedges contributes 17.7% upstream and 22.2% downstream to the Sag River. At the upstream with a frozen active layer or transient layer (including seasonal intrasediment ice), lower active layer water (mineral-rich) and upper active layer water (organic-rich) accounted for 31.5% and 18.1%, respectively. By contrast, at the downstream, the contribution of active layer water was 26.9%, which was similar to that of the other sources. The sources and flowpaths of Arctic freshwater affect changes in the geochemical characteristics of the freshwater, which is channeled to the Arctic Ocean through major Arctic rivers. This study quantitatively assesses permafrost ice wedge melt in an Arctic basin and provides insights to facilitate investigations of hydrological processes and geochemical changes associated with climate change in Arctic water systems.