Acoustic tomography in the Greenland Sea
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Authors
Joseph, John E.
Subjects
Acoustic tomography
Ocean acoustics
Ocean acoustics
Advisors
Chiu, Ching-Sang
Nystuen, Jeffrey A.
Date of Issue
1991-06
Date
June 1991
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
A six transceiver ocean acoustic tomography array was deployed to monitor ocean ventilation and circulation over the 1988-89 winter cooling season. A stochastic inverse method computer code which attains a solution by minimizing mean square error is used to perform inversions of the Greenland Sea tomography data. A computer simulated ocean is used to evaluate various aspects of system performance. We first consider the advantages and problems associated with using a ray theory based algorithm. Next, we made two adjustments to our inversion code and discuss the effects on system performance. The first adjustment allows for layers of different thicknesses in the inverse solution to increase the density of estimates in regions of interest. The second adjustment allows the estimator to expect variability of the unknown field to decrease exponentially with depth. The ray theory based algorithm is an adequate method of modeling ray paths in the Greenland Sea, but has limitations. Reliability of ray paths degrades as launch angles become shallower and if strong gradients and rapidly changing gradients in sound speed are present in the vicinity of the transceiver elements. A set of Greenland Sea data between one transceiver pair was processed. Although only three groups of eigenrays are involved, initial inversion results indicate the estimator detects seasonal variations and synoptic scale events occurring at time scales greater than 20 days, however, solutions show wide fluctuations at shorter times.
Type
Thesis
Description
Series/Report No
Department
Oceanography
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Funder
Format
55 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.