Spencer, Laura Jean (2014-11). Water-Column Inertial and Sub-Inertial Oceanic Response to Hurricane Isaac in the Deepwater Gulf of Mexico. Master's Thesis.
Thesis
Tropical Storm Isaac entered the Gulf of Mexico on 27 August 2012 and strengthened to become a Category 1 hurricane shortly before making landfall in southern Louisiana. Hurricane Isaac approached Southwest Pass near the mouth of the Mississippi River on August 29, 2012 at 00:00 UTC. The center of the storm then moved westward before making landfall eight hours later at Port Fourchon, LA. On August 28, 2012 at approximately 18:00 UTC, Hurricane Isaac passed directly over the center of a mooring array in a northwesterly trajectory. As part of the Gulf Integrated Spill Research Program, six deepwater moorings featuring upward-looking 75 kHz Acoustic Doppler Current Profilers were deployed in water depths between 836 m and 1690 m in the Mississippi Fan region of the northern Gulf of Mexico in July 2012. Each of the six moorings featured 3 Aanderaa RCM current meters. One current meter was located near the bottom, the next positioned approximately 180 m shallower, then the last positioned an additional 200 m shallower. One mooring featured four InterOcean S4A current meters positioned 100 m apart between 790 m and 1090 m. Maximum current speeds of 41.3 cm/s at 100 m, 35.5 cm/s at 300 m, and 32.7 cm/s at 500 m depth were observed during the passage of the Hurricane Isaac. Maximum bottom current speeds measured from Aanderaa RCMs ranged between 16.1 cm/s at 1645 m depth and 34.0 cm/s at 1020 m depth. Inertial band oscillations (1/2-2 days) are seen to 800 m depths, with energy propagation speeds on the order of 30 m/day vertically and 5.7 km/day horizontally. A blue shift in the effective frequency to 1.11f is observed in the near-inertial band in the wake of Hurricane Isaac. Wavelet analyses of the time-series records indicate two subinertial oscillations (2-5 days and 5-12 days) initiated throughout the water-column at the time of the storms closest approach that persist for approximately one week. Each sub-inertial band response was fundamentally different from the near-inertial response to Hurricane Isaac and showed a strong barotropic response.
