Spatial and Temporal Variability in Dominant Heat Fluxes in Arctic Rivers

Abstract:

River temperature, critical for understanding aquatic biological, physical, and chemical processes, is a function of various heat transfer mechanisms that occur between water and its surrounding environment. The influences of these heat fluxes vary over both time and space, creating thermal heterogeneity critical in establishing hot spots and hot moments for solutes. To better understand how climate change may affect this heterogeneity in arctic river temperatures, we developed an arctic specific process based river temperature model that accounts for spatial and temporal variability in lateral inflows as well as atmospheric and bed conduction fluxes. Preliminary calibration results show that dominant heat fluxes vary with time and location within the model domain, but is primarily driven by the highly variable flow regimes common in the arctic. Based on 2 years of observations and a calibrated model for the Kuparuk River, Alaska, we more specifically found surface heat fluxes dominate the spatial temperature responses for lower flows within the lower order portion of the system while lateral inflows dictate the variability in the temporal response. In the higher order portion of the basin, we have found that lateral inflows are important for understanding volumes of water spatially throughout the study reach; however, surface fluxes dominate temperature responses over time.