Analysis of Acoustic Propagation in the Region of the New England Continental Shelfbreak
Abstract
The Shelfbreak Front PRIMER Experiment, fielded south of Nantucket Island, MA during July and August of 1996, combined acoustic data from a moored array of sources and receivers with simultaneous high-resolution oceanographic measurements. This thesis addresses two primary goals of the experiment, understanding the regional complexities of acoustic propagation and tomographic inversions. Additionally, a new method for predicting acoustic coherence is suggested. Analysis of 400 Hz acoustic receptions and detailed forward propagation modeling demonstrate that both shelfbreak front and non-linear internal wave packets produce strong coupling between the acoustic waveguide modes. Arrival time wander and signal spread vary due 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 hinders detailed tomographic inversion. Instead, simplified methods based on only the mode arrival wander 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1999
- Accession Number
- ADA376669
Entities
People
- Brian J. Sperry
Organizations
- Massachusetts Institute of Technology