Temperature and conductivity profiles from Toolik Lake, Alaska, during winter 2023-2024.

Conductivity, temperature, depth (CTD) profiles were obtained during winter 2023-2024 using a free falling YSI Castaway profiler with resolution and accuracy of temperature 0.01oC and +0.05oC respectively and of specific conductance 1 µS cm-1 and 0.25% + 5 µS cm-1, respectively. Sampling is at 5 Hz with data averaged in 30 cm bins. The data are used to describe the structure of temperature, specific conductance, and density in an ice-covered lake and to calculate the likelihood of double diffusive convection. Data here were taken at 4 m, 10m and 15 m sites in November 2023 and monthly in 2024 at either nearby 15 or 24 m deep sites while the lake remained ice-covered. The ten meter deep site has latitude and longitude 68.62730, -149.60248, the four meter deep site is 68.63282, -149.59967, the 15 meter deep site is 68.62962, -149.61127, and the ~24 m deep site is 68.629080, -149.613867.