Observing Fine-Scale Lake Ice-Out Dynamics in the Lower Kuskokwim River Basin, Alaska

The formation and thaw of lake ice plays a critical role in the hydrology, ecology, and subsistence activities of northern regions. However, little research has examined ice phenology in small water bodies and complex deltaic environments, though these areas are particularly responsive to climate changes and could provide early indicators of broader environmental shifts. In this study, we use Sentinel-2 imagery to map the timing of lake ice-out in 145955 lakes in the Lower Kuskokwim River Basin in southwest Alaska from 2018 to 2023. The average ice-out date across all lakes over the entire study period is May 14, with a standard deviation of 9.6 days and an average uncertainty due to cloud cover or missing data of 4.4 days. Ice-out timing shows significant interannual variability that is largely driven by air temperature, with the earliest mean ice-out date occurring on May 6 in 2019 and the latest on May 27 in 2023. The annual spatial variability in ice-out timing also varies, with 2019 and 2023 exhibiting much wider variability than other years. We find a correlation between ice-out timing and lake size, with small lakes (< 1 km²) losing ice on average 6 days earlier than large lakes. We also assess the predictability of ice-out timing using the 0°C threshold date and find that smaller lakes respond faster to spring warming than larger lakes. Overall, our findings provide a novel estimate of spatial and temporal variability in ice-out timing in a complex wetland environment, with implications for both ice-out prediction in a warming climate and the importance of including smaller lakes in ice phenology analyses.

Duke Scholars

Author Sarah Cooley Earth and Climate Sciences