Heat flux dynamics in low Arcitc rivers

• Main Authors: King, Tyler, Rasmussen, Mitchell, Overbeck, Levi, Kane, Douglas
• Format: Text
• Language: unknown
• Published: DigitalCommons@USU 2017
• Subjects: Earth Sciences; Environmental Engineering; Environmental Sciences; Hydraulic Engineering; Life Sciences; Arctic; Brooks Range; Climate change; Alaska
• Online Access: https://digitalcommons.usu.edu/runoff/2017/2017Posters/33

The impacts of climate change on Arctic river temperatures and the resulting influences on biogeochemical cycling and habitat suitability require research into controlling heat fluxes between Arctic rivers and their surroundings. Instrumentation of the Kuparuk River in the foothills of the Brooks Range, Alaska, USA, during the 2013 - 2015 open water seasons provided data required to populate and calibrate an instream temperature model. This model accounts for radiative, sensible, and latent heat fluxes at the air-water interface, conductive and friction heat fluxes at the water-sediment interface, and lateral inflows of heat and mass from surface and subsurface hillslope drainage adjacent to the river. Model outputs reproduce observed river temperature dynamics throughout the watershed under high flows, with radiative heat fluxes dominating the total energy balance and lateral inflows contributing significantly following rainy periods of elevated hillslope drainage. Under low flows, however, observed river temperatures in the headwater portion of the watershed were significantly buffered when compared with simulated river temperatures that produced daily ranges in river temperatures up to 15 °C greater than were observed. River temperature observations were reproduced when advective heat fluxes at the water-sediment interface were incorporated, indicating that hyporheic exchange provides significant buffering capacity in Arctic river temperatures under low flows. The influence of hyporheic exchange on river temperature depends on residence times and the proximity of flow paths to the frozen soils below the river bed. Therefore, Arctic river temperatures may be significantly affected by alterations in sub-surface thaw, atmospheric conditions, and hillslope hydrology – all of which are projected to accompany changes in Arctic climate.