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 T _w 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 0.16°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 T _a 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. [ABSTRACT FROM AUTHOR]