Changing River Ice Seasonality and Impacts on Interior Alaskan Communities

Subsistence harvesters in high latitudes rely on frozen rivers for winter access to local resources. During recent decades, interior Alaskan residents have observed changes in river ice regimes that are significant hindrances to travel and subsistence practices. We used remote sensing in combination with local observations to examine changes in seasonality of river breakup and freeze-up and to assess the implications on travel for subsistence harvesters. Spring and autumn air temperatures, respectively, were found to impact timing of breakup (-2.0 days degrees C-1) and freeze-up (+2.0 days degrees C-1). Spring air temperatures have increased by 0.2 degrees-0.6 degrees C decade(-1) over the last 62-93 years, depending on study area and time period. Local observations indicate that the breakup season has advanced by about 6 days over the last century. Autumn air temperatures have not changed over the long term, but have been generally warmer over the last 15 years. Over various time periods throughout the last century, we found no change in freeze-up timing for some communities, whereas other communities showed delays of 1.0-2.1 days decade(-1). The length of time the river was unsafe for travel during the freeze-up season was 2 to 3 times greater than during breakup. The duration of river ice cover for safe travel has declined over the last century and is expected to decline further as the climate continues to warm, thereby presenting new challenges to accessing subsistence resources and necessitating community adaptation.