CHARACTERIZATION OF THERMAL ANOMALIES IN A TUNDRA RIVER USING THERMAL INFRARED IMAGERY

Spatial heterogeneity in river temperatures provide important thermal refuge habitat for cold-water aquatic taxa in many temperate and tropical rivers. As climate change progresses in the Arctic, it is feasible that the endemic fish populations will seek out similar refuges from increasing river temperatures during dry periods throughout summer months. However, little is known about the occurrence, distribution, and drivers of thermal heterogeneity of Arctic Rivers. In this study we present an analysis of thermal anomalies for a 35 km long reach of the Kuparuk River, Alaska. Using high-resolution thermal Infrared (TIR) imagery from repeat aerial surveys we identified the spatial distribution and magnitude of thermal anomalies under a wide range of flow conditions. We classified these thermal anomalies based on associated hydraulic/hydrologic features to develop a conceptual model of the processes that produce thermal heterogeneity in Arctic rivers, and how these processes vary with hydrologic condition. Our preliminary results show that 1) nearly all thermal anomalies were colder than mean river temperatures, 2) thermal anomalies were found to be associated with four major hydraulic/hydrologic features: tributary and water track mouths, surface transient storage zones, and the downstream side of gravel bars, 3) there were limited differences in the magnitude of thermal anomalies across hydraulic/hydrologic features, 4) the abundance and severity of thermal anomalies were inversely related to river discharge, and 5) the abundance of thermal anomalies in response to changes in discharge varied most for gravel bars and least for tributaries. These findings show that thermal anomalies are abundant under current hydrometeorologic conditions, and highlight the influence of permafrost, landscape connectivity, and groundwater/surface water interactions on producing spatial thermal heterogeneity. Further research is required to determine the sensitivity of currently observed thermal anomalies to projected changes in basin characteristics, such as increased depth of permafrost thaw and alterations to hydrologic regimes, and to determine the efficacy of these thermal anomalies as thermal refugia.