Warming Water in Arctic Terrestrial Rivers under Climate Change

Recent years have seen an obvious warming trend in the Arctic. Streamflow and water temperature T-w are important parameters representing the changes of Arctic rivers under climate change. However, few quantitative assessments of changes in river Tw have been conducted at the pan-Arctic scale. To carry out such an assessment, this study used a modeling framework combining a land process model [the coupled hydrological and biogeochemical model (CHANGE)] with models of river discharge Q, ice cover, and T-w dynamics. The T-w model was improved by incorporating heat exchange at the air-water interface and heat advection from upstream through the channel network. The model was applied to pan-Arctic terrestrial rivers flowing into the Arctic Ocean over the period 1979-2013 and quantitatively assessed trends of T-w at regional and pan-Arctic scales. The simulated T-w values were consistent with observations at the mouths of major pan-Arctic rivers. The model simulations indicated a warming trend of T-w by 0.168 degrees C decade(-1) at the outlets of the pan-Arctic rivers, including widespread spatial warming consistent with increased air temperature T-a. The strong impact of T-a on T-w was verified by model sensitivity analysis based on various scenarios involving changes in the Ta and Q forcings. Finally, this study demonstrated the warming of T-w in Arctic rivers induced by T-a warming, suggesting the potential for warming T-w of Arctic rivers under future climate change scenarios.