Analysis of acoustic propagation in the region of the New England continental shelfbreak
Citable URI
https://hdl.handle.net/1912/4696Location
Mid-Atlantic BightDOI
10.1575/1912/4696Keyword
Underwater acoustics; Continental shelfAbstract
During July and August of 1996, a large acoustics/physical oceanography experiment
was fielded in the Mid-Atlantic Bight, south of Nantucket Island, MA. Known as
the Shelfbreak Front PRIMER Experiment, the study combined acoustic data from
a moored array of sources and receivers with very high resolution physical oceanographic measurements. This thesis addresses two of the primary goals of the experiment, explaining the properties of acoustic propagation in the region, and tomographic inversion of the acoustic data. In addition, this thesis develops a new method
for predicting acoustic coherence in such regions.
Receptions from two 400 Hz tomography sources, transmitting from the continental slope onto the shelf, are analyzed. This data, along with forward propagation
modeling utilizing SeaSoar thermohaline measurements, reveal that both the shelfbreak
front and tidally-generated soliton packets produce stronger coupling between
the acoustic waveguide modes than expected. Arrival time wander and signal spread
show variability attributable to the presence of a shelf water meander, changes in
frontal configuration, and variability in the soliton field. The highly-coupled nature
of the acoustic mode propagation prevents detailed tomographic inversion. Instead,
methods based on only the wander of the mode arrivals are used to estimate path-averaged
temperatures and internal tide "strength".
The modal phase structure function is introduced as a useful proxy for acoustic
coherence, and is related via an integral transform to the environmental sound speed
correlation function. Advantages of the method are its flexibility and division of the
problem into independent contributions, such as from the water column and seabed.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1999
Suggested Citation
Thesis: Sperry, Brian J., "Analysis of acoustic propagation in the region of the New England continental shelfbreak", 1999-06, DOI:10.1575/1912/4696, https://hdl.handle.net/1912/4696Related items
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