Open flow at forty below: Hydrogeomorphic processes influencing open water zones on the Tanana River

Authors: Scragg, Matthew. University of Alaska Fairbanks; Arp, Christopher. WERC, UAF; Bondurant, Allen. WERC, UAF. Brown, Dana. IARC, UAF. Toniolo, Horacio. WERC, UAF; Sullivan, Taylor. CRREL; Engram, Melanie. WERC, UAF

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Abstract

Frozen rivers provide a crucial transportation corridor for residents of interior Alaska throughout the winter. Some observations have indicated a shorter ice season and decrease in overall river ice thickness on interior Alaskan rivers in recent decades, which impacts subsistence, recreational, and commercial activities. Open water zones (OWZs) in an otherwise frozen river (i.e., open leads) are common and unpredictable, and may occur at any time throughout the winter, but are more common in early and late winter. The temporal and spatial occurrence of OWZs are poorly understood, as well as the climatic, hydrologic, and geomorphic factors that influence their occurrence. One persistent late freezing open water zone on the Tanana River near Fairbanks, Alaska, provides an opportunity to increase our understanding of the processes contributing to the formation of OWZs. We measured channel geometry, ice thickness, and hydraulic conditions at this site throughout the 2023-2024 winter season to identify the physical properties and related mechanisms that control the occurrence of this OWZ. We used cameras to monitor ice conditions throughout the "23/24" season and to validate optical and microwave remote sensing data.

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