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Abstract Timing and completeness of freeze‐up on northern rivers impact winter travel and indicate responses to climate change. Open‐water zones (OWZs) within ice‐covered rivers are hazardous and may be increasing in extent and persistence. To better understand the distribution, variability, and mechanisms of OWZs, we selected nine reaches totaling 380 river‐km for remote sensing analysis and field studies in western Alaska. We initially identified 48 OWZs from November 2022 optical imagery, inventoried their persistence into late winter and interannual consistency over previous years, and at a subset measured ice thickness, water depth and velocity, and physicochemistry. The most consistent locations of OWZ formation occurred below sharp bends and channel constrictions, whereas locations associated with river bars and eroding banks were more transient. Of 359 OWZs identified in early winter over 6 years, 8% persisted into late winter―all on the Yukon River mainstem. Although several OWZs were in locations where we anticipated groundwater influence, we found no field data indication of groundwater upwelling. Observations of jumble ice upstream of many OWZs led us to examine freeze‐up ice jam locations in optical imagery, which showed strong correspondence to downstream OWZs. We hypothesize that reaches downstream of ice jams are much slower to freeze‐over due to restricted ice transport and high turbulence caused by channel form and ice‐affected hydraulics. Future work should focus on evaluation of this and other competing hypothesis at both reach and river network scales to predict OWZ locations and occurrence relative to other processes affecting river freeze‐up in northern climates. 

Abstract Ice formation is generally considered to exclude many particles and most solutes and thus be relatively pure compared to ambient waters. Because river ice forms by a combination of thermal and mechanical processes, some level of sediment entrainment in the ice column is likely, though reports of sediment in river ice are limited. We observed high and sporadic levels of silt and sand in ice of the Kuskokwim and Tanana rivers (Alaska, the United States) during routine field studies. These observations led us to make a more comprehensive survey of sediment entrainment in river ice of the Kuskokwim and Yukon rivers and several of their tributaries. We collected and subsampled 48 ice cores from 19 different river locations in March 2023, which included concurrent measurements of water turbidity, velocity, and depth. Approximately 60% of cores contained detectable levels of sediment, averaging 438 mg/L with median concentrations exceeding 1000 mg/L in three cores from the Yukon and Kuskokwim main stems. Many cores had even higher concentrations at certain intervals, with seven cores having subsamples exceeding 2000 mg/L; these were often located in the middle or lower portion of the ice column. Jumble ice, formed mechanically by frazil‐pan jamming during freeze‐up, was generally the best predictor of higher sediment entrainment, and these locations often had higher under‐ice velocities and depths. Our observation of high and widespread sediment entrainment in northern river ice, particularly in jumble‐ice fields, may have implications for sediment transport regimes, ice strength and transportation safety, and how rivers break up in the springtime. 

Youth-focused community and citizen science (CCS) is increasingly used to promote science learning and to increase the accessibility of the tools of scientific research among historically marginalized and underserved communities. CCS projects are frequently categorized according to their level of public participation and their distribution of power between professional scientists and participants from collaborative and co-created projects to projects where participants have limited roles within the science process. In this study, we examined how two different CCS models, a contributory design and a co-created design, influenced science self-efficacy and science interest among youth CCS participants. We administered surveys and conducted post-program interviews with youth participation in two different CCS projects in Alaska, the Winterberry Project and Fresh Eyes on Ice, each with a contributory and a co-created model. We found that youth participating in co-created CCS projects reflected more often on their science self-efficacy than did youth in contributory projects. The CCS program model did not influence youths’ science interest, which grew after participating in both contributory and co-created projects. Our findings suggest that when youth have more power and agency to make decisions in the science process, as in co-created projects, they have greater confidence in their abilities to conduct science. Further, participating in CCS projects excites and engages youth in science learning, regardless of the CCS program design. 

Abstract. The formation, growth, and decay of freshwater ice on lakes andrivers are fundamental processes of northern regions with wide-rangingimplications for socio-ecological systems. Ice thickness at the end ofwinter is perhaps the best integration of cold-season weather and climate,while the duration of thick and growing ice cover is a useful indicator forthe winter travel and recreation season. Both maximum ice thickness (MIT)and ice travel duration (ITD) can be estimated from temperature-driven icegrowth curves fit to ice thickness observations. We simulated and analyzedice growth curves based on ice thickness data collected from a range ofobservation programs throughout Alaska spanning the past 20–60 years tounderstand patterns and trends in lake and river ice. Results suggestreductions in MIT (thinning) in several northern, interior, and coastalregions of Alaska and overall greater interannual variability in riverscompared to lakes. Interior regions generally showed less variability in MITand even slightly increasing trends in at least one river site. Average ITDranged from 214 d in the northernmost lakes to 114 d acrosssouthernmost lakes, with significant decreases in duration for half ofsites. River ITD showed low regional variability but high interannualvariability, underscoring the challenges with predictingseasonally consistent river travel. Standardization and analysis of theseice observation data provide a comprehensive summary for understandingchanges in winter climate and its impact on freshwater ice services.