Climate-driven future changes in Arctic river discharges using hydrological modelling and CMIP6 projections

Arctic amplification is intensifying the hydrological cycle of high-latitude river systems, yet quantitative projections of future discharge remain scarce for many Arctic catchments. This study quantifies the impacts of climate change on the discharge regime of the Tana River, a pristine transboundary Arctic catchment in northern Fennoscandia, using the SWAT + hydrological model driven by five CMIP6 GCMs and an ensemble under four SSP scenarios. The model was calibrated and validated against observed daily discharge at three gauging stations. The findings demonstrate that the Tana River’s discharge regime is already on a trajectory of significant change. The future simulations reveal systematic, SSP-dependent changes in the monthly discharge distribution, seasonal flow patterns, and annual projections through 2100. The timing of peak flow is projected to shift from June to May across most of the GCMs and scenarios, reflecting earlier snowmelt driven by rising temperatures. Seasonal analysis indicates increased flows in winter, spring, and autumn, and decreased flows in summer. By the end of the 21st century, annual discharge, precipitation and mean temperature are projected to increase, while the snow fraction is projected to decline. Under different SSPs, discharge exhibits statistically significant increasing trends, with Pettitt tests identifying change points around mid-century. These predicted changes may have significant implications for the ecosystem, flood risk, and water resource management in the Arctic region.