Isabella Anna Oleksy, David C. Richardson

Temperate lakes worldwide are losing ice cover but the implications for under-ice thermal dynamics are poorly constrained. Using a 90-year record of ice phenology from a temperate lake, we examined trends, variability, and drivers of ice phenology. The onset of ice formation decreased by 23 days century-1 which can be largely attributed to warming air temperatures. Ice-off date has become substantially more variable with spring air temperatures and cumulative February through April snowfall explaining over 80% of the variation in timing. As a result of changing ice phenology, total ice duration contracted by a month and more than doubled in inter-annual variability. Using weekly under-ice temperature profiles for the most recent 36 years, shorter ice duration decreased winter inverse stratification and extended the spring mixing period.