Modeling changes in ice dynamics and subsurface thermal structure in Lake Michigan-Huron between 1979 and 2021

Abstract The world’s largest lakes, including the Laurentian Great Lakes, have experienced significant surface warming and loss of ice cover over last several decades. Although changing conditions received substantial research interest, changes below remain largely unexplored, despite their importance for turbulent mixing, nutrient cycling, primary production. In this study, we investigate in subsurface thermal structure timing Lake Michigan-Huron related to ongoing climate warming. This work utilizes atmospheric reanalysis data drive Lakes Finite Volume Community Ocean Model (GL-FVCOM), providing three-dimensional hydrodynamic simulations between 1979 2021. Results are used analyze trends temperature dynamics, revealing annually averaged (? 2.1– ? 5.2%/decade), thickness 0.68 – 2.0 cm/decade), (+ 0.47– + 0.51 $$^\circ{\rm C}$$ ? C /decade), bottom 0.26– 0.29 /decade) 40 years, especially ecologically important bays (e.g., Green Bay, Saginaw Bay). Significant was observed at all depth layers (0–270 m), with epilimnion hypolimnion that agreed well recent analysis observational Michigan. Shifting stratification dynamics led dramatic modelled overturning behavior, earlier spring turnover dates 2.2– 7.5 days/decade) later fall 2.5– 6.3 a net lengthening stratified period. study presents one most comprehensive analyses temperatures date, context future modelling coastal management efforts region.