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.
","abstract_html":"<p>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.</p>","abstract_has_math":false,"creators":["Earls, Jordan"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Masters Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Maarten C. Buijsman","Stephan D. Howden","Davin J. Wallace"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-12-01T08:00:00Z","date_published":"2019-12-01T08:00:00Z","updated_at":"2026-07-24T05:45:12Z","subjects":["Near-inertial waves","upwelling","downwelling","EOF","Physical Oceanography","Gulf of Mexico","Oceanography","Other Physics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aquila.usm.edu/masters_theses/699","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Maarten C. Buijsman","Stephan D. Howden","Davin J. Wallace"]},{"key":"dc:creator","label":"Author","values":["Earls, Jordan"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2019-10-17T07:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Masters Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Near-inertial waves","upwelling","downwelling","EOF","Physical Oceanography","Gulf of Mexico","Oceanography","Other Physics"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://aquila.usm.edu/masters_theses/699"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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.
"]},{"key":"dc:title","label":"Title","values":["The Variability of High-Frequency Motions and Their Interactions with the Mesoscale on the Mississippi Shelf"]}]}],"canonical_facts":{"dc:contributor":["Maarten C. Buijsman","Stephan D. Howden","Davin J. Wallace"],"dc:creator":["Earls, Jordan"],"dc:date.available":["2019-10-17T07:00:00Z"],"dc:description.abstract":["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.
"],"dc:identifier":["https://aquila.usm.edu/masters_theses/699"],"dc:subject":["Near-inertial waves","upwelling","downwelling","EOF","Physical Oceanography","Gulf of Mexico","Oceanography","Other Physics"],"dc:title":["The Variability of High-Frequency Motions and Their Interactions with the Mesoscale on the Mississippi Shelf"],"thesis:degree_level":["Masters Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:45:12Z"}