Warming Water in Arctic Terrestrial Rivers under Climate Change

Abstract

Abstract Recent years have seen an obvious warming trend in the Arctic. Streamflow and water temperature Tw 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 Tw dynamics. The Tw 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 Tw at regional and pan-Arctic scales. The simulated Tw values were consistent with observations at the mouths of major pan-Arctic rivers. The model simulations indicated a warming trend of Tw by 0.16°C decade−1 at the outlets of the pan-Arctic rivers, including widespread spatial warming consistent with increased air temperature Ta. The strong impact of Ta on Tw 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 Tw in Arctic rivers induced by Ta warming, suggesting the potential for warming Tw of Arctic rivers under future climate change scenarios.