The Hydrologic Response to a Meteotsunami in an Isolated Wetland: Beaver Island in Lake Michigan, USA

Meteotsunamis are both a well-known and poorly understood phenomenon. In particular, the influence of and disturbance by meteotsunamis on isolated coastal wetlands is largely unknown. This paper documents a case illustrating how water levels in an incipient foredune/swale complex in northern Lake Michigan responded to a meteotsunami event. We identified potential meteotsunami influence on wetland water levels through slope-break and wavelet analysis, verified the presence of meteotsunami waves at surrounding lake water level gauge stations with wavelet analysis, analyzed both regional and small-scale meteorological data to establish what source of atmospheric forcing resulted in meteotsunami formation, and used a hydrodynamic model to simulate lake surface response and meteotsunami generation. On 20 July 2019, an atmospheric bore wave propagating away from a convective storm formed a meteotsunami event in Lake Michigan that struck Sand Bay, Beaver Island and generated a 36 cm increase in subsurface wetland water levels over the course of a 1-hr period. The potential for multiple sources of meteorological forcing and secondary wave refraction highlights several challenges with predicting generation of and effects from meteotsunami events. Additionally, while irregular, the effects of these events on isolated wetland systems have the potential to alter hydrologic and sediment budgets, vegetation growth, and dune stability; yet meteotsunami influence on isolated wetlands is an understudied phenomenon. The event presented in this study make a strong case for focused research on coastal wetland response to meteotsunamis (and meteotsunami-like events) to address this understudied impact given its implications for coastal processes and resiliency.