Thermal Response of Lakes to Cyclic Environmental Forcing

Abstract Predicting the thermal response of lakes to cyclic environmental forcing and their expected global changes requires precise mathematical expressions. We apply a hybrid approach, based on theoretical analysis and direct measurements, including the role of lake's thermal stratification. We explore the equilibrium solution of the energy balance equation, achieved when changes in stored heat are negligible, governed by environmental conditions. As environmental forcing varies, lake surface temperature depart from equilibrium, with a time delay and reduced amplitude, depending on the ratio between the forcing period and the lake's thermal response time, and its dependency on lake/thermocline depth and wind speed. These formulations were tested based on 2 years of eddy covariance data from two neighboring Mediterranean lakes differing in physical structure, a deep and shallow lake. Finally, we provide tools for estimating surface temperature and evaporation rates across various timescales, stratification patterns, and global environmental changes.