Mid-Century Alaskan hydrology in transition: how changing precipitation and evapotranspiration patterns are projected to reshape seasonal streamflow
Climate change is profoundly reshaping Arctic hydrology, necessitating a comprehensive understanding of evolving hydrological conditions for effective planning and resilience strategies. However, the majority of regional or global river models lack the necessary resolution to accurately project local conditions. In this study, we employ a series of high-resolution models to forecast river discharge trends by mid-century. Leveraging the mizuRoute river routing model, forced by output from a 4km resolution regional climate model, we compare results between historical (1990-2021) and mid-century (2034-2065) time frames across six future scenarios. These scenarios encompass two pseudo-global warming and four dynamically downscaled large ensemble models, under a "middle of the road" emission scenario. Our findings indicate a projected 6% increase in annual flow to the ocean, with the most significant increases anticipated during April and October. Notably, one-third of spring gauges exhibit escalating discharge across future scenarios, while half of all gauges show increased discharge in the fall. This increase is attributed to amplified rainfall including changing weather patterns and a transition from snow to rain in the spring and fall, coupled with heightened snowmelt. Rising evapotranspiration moderates the magnitude of discharge changes cause by changes in precipitation. Furthermore, the centroid of discharge is shifting earlier in the year at two-thirds of all gauges, despite peak discharge occurring later. Increasing discharge in fall, winter, and spring underscores the extensive alteration of hydrological fluxes in the Arctic.