Observations of Large Amplitude Sea Level Oscillations Generated by Meteorological Perturbations off the Coast of Louisiana

Sea-level oscillations with periods in the range of minutes to hours associated with strong atmospheric perturbations have the potential to significantly impact the coast and can be amplified through changes in the bathymetry where the effects of shoaling become significant. Additional resonance mechanisms dependent a combination of factors such as the speed of and direction of the atmospheric perturbation, bathymetry and geometry of the coast can further amplify these waves where the most common resonance mechanisms are Proudman, Greenspan, and Harbor resonance. Meteotsunamis are considered a multi-resonant phenomena in which the combination of an atmospheric perturbation as well as one or more resonance mechanisms generate waves of significant height that can have a destructive impact to the coast. A number of high resolution sensors RBR pressure gauges and RDI Acoustic Doppler Profilers were deployed along the coast of Louisiana during winter and spring of 2017-2020. The Northern Gulf of Mexico, during late winter and early spring months exhibits a high level of meteorological activity, with cold fronts passing approximately every 2 weeks over the region. The experiment included multiple instrument deployments at locations selected to capture the response of the coastal ocean. The goal of the experiment was to identify significant sea level oscillations within the data set that are related to an atmospheric disturbance traveling through the area. Time series records of pressure and velocity as well as available meteorological data in the form of atmospheric pressure, atmospheric temperature, wind speed, wind direction, radar imagery and reflectivity are used in an effort to identify the sea level oscillations of interest. Analysis of the data shows a significant number events in which there is a significant sea level oscillation observed typically associated with a passing atmospheric perturbation in the form of a front, squall line, or convection cell. Empirical equations along with flow measurements are analyzed in order to understand the relationship between these large amplitude waves and sediment re-suspension. Atmospheric perturbations were observed frequently throughout the experiment generating significant sea level oscillations as often as three times in one month.