Inflatable Midlake

Microstructure profiling in the middle of Lake Michigan

Near-inertial internal waves are ubiquitous features in both large lakes and oceans. In large thermally-stratified lakes such as Lake Michigan, these basin-scale waves create strong near-surface currents that rotate clockwise (in the northern hemisphere) over a near-inertial period (~17.5 hours for Lake Michigan). The influence of these basin-scale waves, for which the thermocline movement represents a spinning coin, is particularly strong in the offshore waters, where the spiraling near-surface currents can have tide-like regularity, with magnitudes exceeding 50 cm/s. While these waves are readily observed in velocity and temperature measurements taken in large lakes, their influence on vertical mixing and lateral dispersion is not well-understood. This project examines two related hypotheses: (1) strong near-inertial shear drives cross-thermocline mixing; (2) lateral dispersion is enhanced by vertical shear associated with near-inertial wave currents. Our approach for this project is to carry out a set of field measurements involving moored instruments and microstructure cruises, as well as a large-scale dye and drifter release carried out in the center of Lake Michigan’s southern basin.

Funding

National Science Foundation, Division of Ocean Sciences, Physical Oceanography Program

Collaborators

Nathan Hawley, NOAA Great Lakes Environmental Research Laboratory

Selected Publications

A Year of Internal Poincaré Waves in Southern Lake Michigan
Choi, J. M., C. D. Troy, T.-C. Hsieh, N. Hawley, and M. J. McCormick Journal of Geophysical Research PDF  Online Article

Cross-shelf thermal structure in Lake Michigan during the stratified periods
Troy, C.D., Ahmed, S., Hawley, N., and A. Goodwell Journal of Geophysical Research, VOL. 117, C02028, 16 PP., 2012 PDF  Online Article

Lateral dispersion of dye and drifters in the center of a very large lake
Choi, J.M., C.D. Troy, N. Hawley, M. McCormick, and M.G. Wells Limnology and Oceanography PDF  Online Article

Shear dispersion from near‐inertial internal Poincaré waves in large lakes
Choi, J. M., Troy, C. D., & Hawley, N. Limnology and Oceanography, , 60(6), 2222-2235 PDF  Online Article

Spatial structure of internal Poincaré waves in Lake Michigan
Ahmed, S., C.D. Troy, and N. Hawley Environmental Fluid Mechanics, , 14:1229 PDF  Online Article