Tidal controlled temperature changes in Diamond Lake in Minneapolis, Minnesota, USA

Autonomous temperature sensors, data loggers, have been placed in the Diamond Lake in Minnesota, Minneapolis, USA. The depth was shallow (<1 m) at the measurement site. Hourly measurements revealed the temperature changes of the ice frozen over the lake as well as the temperature record of the water under the ice. The ice that formed over the lake was soon covered with the snow. Snow isolated the ice from the daily air temperature changes. Temperature sensors were about 1-2 inches apart attached to the plastic rope tied to the floater on one side and anchored with the piece of metal on the other side of the rope. Sensors that were frozen deeper within the ice showed dumped and delayed thermal fluctuation from the surface. The sensors that were frozen at the bottom within the ice showed continuous, almost constant, temperature near freezing. However, all of the sensors that were within the liquid water below the ice showed thermal variation indicating significant 12 and 24 hour periods. We have correlated these variations with the tidal forces from the solar system bodies and found that during the maximum of the tidal gravity forces, when both the Moon and the Sun gravity forces were additive, the variation of the temperature correlated with the daily tides. However the daily tidal variation anti correlated when the tidal force from the Sun acted against the tidal force from the Moon. This paper discusses this new observation.