A new study published in the journal Glacies documents why, where, and when the Chena River failed to freeze-over despite very cold temperatures through last year’s historic winter. Following up on studies of open-water on the Yukon, Kuskokwim, and Tanana rivers, Fresh Eyes on Ice scientists sought to better understand why a river close to home doesn’t regularly freeze-up through downtown Fairbanks. Ice data collected by 5^th grade students at the Watershed School helped tell the story.

Most Interior Alaska rivers develop seasonal ice cover through the winter, providing important ecosystem and societal services. A longstanding exception commonly occurs on the Chena River as it flows through the City of Fairbanks, primarily attributed to power-plant effluent that causes ice-free conditions far downstream. Over the winter of 2025–2026, we sought to document the extent of downstream open water in this urban river relative to hydrologic and weather conditions. A combination of satellite imagery and time-lapse cameras show that ice began forming in late October with near complete ice-cover upstream of the discharge zone by early December and open water persisting far downstream (6 km) through most, if not all of, the entire winter. Sensors placed upstream and incrementally downstream of the discharge zone detected water temperatures at 0 °C above and far below (12 km) all winter long, but 200 m downstream averaged 0.8 °C and 1100 m downstream averaged 0.3 °C. Estimated cooling lengths to return to near-freezing temperatures downstream from the power plant were approximately 9 km based on observed water temperature data. Notably, the winter of 2025–2026 ended up being the coldest in Fairbanks history dating back 96 years, despite a long-term trend towards warmer winters. This striking winter context is considered relative to power-plant operations, downstream impacts on freezing, and sources of natural and human-influenced winter open-water occurrence on other northern rivers.