Modelling Changes in Ice Dynamics and Subsurface Thermal Structure in the Laurentian Great Lakes: Investigating the Effects of Climate Warming in Lake Michigan-Huron
Abstract
The Laurentian Great Lakes have experienced significant surface warming and loss of ice cover over the last several decades. Although changing surface conditions have received significant research interest, changes below the surface remain largely unexplored, despite their importance for turbulent mixing, nutrient cycling, and primary production. In this study, we investigate changes in subsurface thermal structure, ice dynamics, and stratification timing in Lake Michigan-Huron related to ongoing climate warming. This work utilizes historical reanalysis forcing data to drive the Great Lakes Finite Volume Community Ocean Model (GL-FVCOM), providing three-dimensional hydrodynamic and ice simulations between 1979 and 2021. Results are used to analyze trends in water temperature and ice cover in Lake Michigan-Huron, revealing dramatic increases in subsurface temperature (+0.1 - 0.5 °C/decade; 0 - 250m depth) and decreases in both ice cover (-1 - 5 %/decade) and ice thickness (-2 - 6 cm/decade) over the last 40 years. Estimated turnover dates suggest that the spring (fall) overturn is occurring earlier (later) in the season, effectively shortening the well-mixed isothermal period. Calculated warming trends are compared to recent analysis of observational data collected in the lake, with strong agreement improving confidence in model results. Modelled changes in lake hydrodynamics, including mixing cycles, benthic temperatures, and mixed layer depth, are linked to observed and predicted shifts in lake ecology (i.e. nutrient cycles, phytoplankton blooms, etc.), highlighting practical applications of study results. This work presents one of the most comprehensive analyses of changes in Great Lakes subsurface temperatures to date, providing important context for future climate modeling and coastal management efforts in the region.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H22I..02C