Monthly and Episodic Dynamics of Summer Circulation in Lake Michigan

Abstract

A comprehensive understanding of lake circulation is fundamental to inform better management of ecological issues and fishery resources in the Great Lakes. In this study, a high‐resolution, wave‐current coupled, three‐dimensional modeling system was applied to investigate the monthly and episodic dynamics of summer circulation in Lake Michigan. Model sensitivities to three wind sources and two grid resolutions against observed current velocities, water temperatures, and significant wave heights in the summer of 2014 were examined. Model performance was validated with additional satellite imageries and current measurements in the summer of 2015. Results indicated that the high‐resolution model driven by the observation‐based winds reproduced lake dynamics most reasonably. In July 2014, a pair of monthly averaged anticyclonic (i.e., clockwise) gyres in the surface layer were simulated in southern Lake Michigan. Analysis indicates that they originate from the wind‐driven, upwelling‐favorable, jet‐like Ekman currents along the west shore, which are connected by the density‐driven basin‐scale circulation. Although river inputs, strait exchanges, waves, grid resolutions, and bathymetric variations influence the monthly surface circulation, their effects are less important than the wind and density‐driven currents. Additional simulations support the predominant impacts of wind and density‐driven currents on lake surface circulation during a strong wind event. Further investigations suggest that lake circulation varies from surface to bottom layers, and this knowledge is significant to the related ecological issues and fishery resources management. The numerical model configured to Lake Michigan is beneficial to understanding dynamics in the Great Lakes system and other large water bodies.

Projected Changes of Water Currents and Circulation in Lake Michigan Under Representative Concentration Pathways Scenarios

“…(2018). A recent study by Mao and Xia (2020) performed a sensitivity analysis of lake circulation to various wind products and depicted the satisfactory performance of the observation‐based Natural Neighboring Method (NNM) winds (Schwab & Morton, 1984) for the circulation modeling in Lake Michigan. Nevertheless, NNM winds were unavailable at a long timescale, unlike the climatic projections.…”

“…A spin-up period of 30 days (i.e., the month of April) is used to stabilize the model and to build the 3D thermal structure of the lake. Most of the physical parametrization in the FVCOM setup here was referred from Mao and Xia (2020). For simplicity, Table 3 lists the basic model setups.…”

“…Subject to the relatively higher human intervention and the complex lake geography, the present study projects the Lake Michigan circulation dynamics where major issues are addressed as follows: (a) future bimonthly variability in the current magnitude during the ice‐free months and (b) projections of the gyre circulation. With a set of validation experiments being conducted during 2010–2019, the Finite‐Volume Community Ocean Model (FVCOM; Chen et al., 2003) configured to Lake Michigan (Mao & Xia, 2020) is implemented for the hydrodynamic projection during 2020–2069. Climate change impacts are incorporated by using one of the Coupled Model Intercomparison Project 5 (CMIP5) model, Geophysical Fluid Dynamics Laboratory‐Global Climate Model (GFDL‐CM3) data products under RCP 4.5 and 8.5 scenarios.…”

“…The seasonal reversal of wind direction generates a distinct circulation pattern in the lake (Miller & Saylor, 1985). Overall, circulation dynamics in Lake Michigan are predominantly governed by winds, variations of lake water densities (i.e., a function of water temperature gradients), and nearshore features (Beletsky & Schwab, 2008;Beletsky et al, 2006;Boyce et al, 1989;Mao & Xia, 2020). Based on the observation from about 100 moored buoys, Beletsky et al (1999) documented the occurrence of stronger winter currents and cyclonic (i.e., counter-clockwise) gyres in Lake Michigan.…”

Impact of the Monthly Variability of the Trent River on the Hydrodynamical Conditions of the Bay of Quinte, Ontario: A Case Study 2016–2019

“…The Finite Volume Community Ocean Model (FVCOM) model developed at the University of Massachusetts-Dartmouth was used for this study [10]. This model is used operationally in the Great Lakes and has been successfully applied to a variety of studies including a 28-year simulation of the Bay of Quinte [6,[11][12][13]. Simulations for this study used river inputs for the 4 main tributaries (the Trent, Moira, Salmon and Napanee rivers), wind and heat flux forcing, and simulated the spring runoff period April-June for 2016-2019 ( Figure 1).…”