The Variability of High-Frequency Motions and Their Interactions with the Mesoscale on the Mississippi Shelf
In this study, we examine the spatial and temporal variability of high-frequency and low-frequency motions across the Mississippi Shelf and how the high-frequency motions are modulated by low-frequency mesoscale motions. For this purpose, we use Acoustic Doppler Current Profiler (ADCP) measurements collected at nearshore (23 m), mid-shelf (60 m), and shelf break (88 m) stations. High-frequency motions are defined as motions with periods less than 36 hours, whereas mesoscale motions have larger periods. The collected datasets are analyzed through bandpass filtering, least square harmonic analysis, spectral analysis, and empirical orthogonal functions (EOF). We find that along-shelf barotropic mesoscale motions contain the most energy. While weak barotropic tidal motions are present, near-inertial motions with diurnal frequencies constitute a significant fraction of the high-frequency motions. In shallow water, the wind-induced near-inertial motions are found to be suppressed by low-frequency downwelling that destroys or subdues the water column stratification. However, the correlation between mesoscale processes and high-frequency motions is not found at the mid-shelf and shelf break stations.
Near-inertial waves, upwelling, downwelling, EOF, Physical Oceanography, Gulf of Mexico, Oceanography, Other Physics
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