Abstract
The mixing and stratification present under ice‐covered lakes during winter can potentially influence the oxygen concentrations in the subsequent spring. During winter, plankton rely on updrafts caused by convection to remain in the photic zone and perform primary production. Thus, there is a crucial link in winter between under‐ice light levels, circulation, and dissolved oxygen (DO) production. Detailed observations of temperature, oxygen, and incoming solar radiation over three winters between 2015 and 2017 suggested that plankton abundance and DO concentrations were maximal near the end of the winter before the ice melted when there was increased under‐ice light and convection. DO was supersaturated by the end of the severe winter of 2015 when the ice cover duration was the longest. In comparison, DO increased but was not saturated in the warmer winters of 2016 and 2017. The spring overturn started when the water column became isothermal and continued until when the mean water column temperature first exceeded 4°C, at which time, hypolimnetic DO depletion started and continued until the fall overturn. The concentration of DO when the water column becomes stratified in spring, along with the timing of the end of spring overturn, are both important initial conditions for summer DO concentrations.