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Winters are changing rapidly with warming temperatures, declining ice duration and dwindling winter snowpack. Ice covers more than half of the world’s lakes each winter, and conditions under ice can impact ecosystem function in subsequent ice-free seasons. Ice cover and inverse stratification impede gas exchange between lake water and the atmosphere, and as a result, respiration can deplete oxygen concentrations under ice. Low oxygen concentrations can impact lake ecology, by creating physiological stress for animals, and biogeochemistry, by shaping redox conditions and nutrient release from sediments. However, the direct impacts of variable snowfall, winter temperatures, and ice duration on oxygen concentrations under lake ice are still poorly understood because multi-year, year-round data are rare. In this study we use 16 lake-years of high frequency temperature and oxygen observations from three lakes of varying morphometry in the southern Rocky Mountains to investigate the drivers of both inter- and intra-annual patterns of bottom-water oxygen concentration under ice. Specifically, we investigate how snowfall, freeze thaw-cycles, and incoming solar radiation impact the light environment and, in turn, oxygen concentration under ice. We found a high degree of inter and intra-annual variability in oxygen dynamics. Additionally, we provide evidence that snow accumulation on the lake surface is associated with decreased light availability and declines in oxygen concentrations, particularly early during the first half of winter. Additionally, in some lake-years we see evidence for hydrologically-mediated or convective mixing that re-oxygenates the bottom waters in mid-winter or the month(s) leading up to ice-clearance. Our study may inform predictions about how lake ecosystems will respond to future changes in winter conditions.