Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean
A series of small depth charges was detonated along a transect from New Zealand to Antarctica over a period of 3 days in late December of 2006. The hydroacoustic signals were recorded by a hydrophone deployed near the source and at a sparse network of permanent hydrophone stations operated by the In...
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fthighwire:oai:open-archive.highwire.org:gji:176/2/478 2023-05-15T14:03:48+02:00 Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean De Groot-Hedlin, C. Blackman, Donna K. Jenkins, C. Scott 2009-02-01 00:00:00.0 text/html http://gji.oxfordjournals.org/cgi/content/short/176/2/478 https://doi.org/10.1111/j.1365-246X.2008.04007.x en eng Oxford University Press http://gji.oxfordjournals.org/cgi/content/short/176/2/478 http://dx.doi.org/10.1111/j.1365-246X.2008.04007.x Copyright (C) 2009, Oxford University Press Marine geoscience TEXT 2009 fthighwire https://doi.org/10.1111/j.1365-246X.2008.04007.x 2013-05-28T10:27:18Z A series of small depth charges was detonated along a transect from New Zealand to Antarctica over a period of 3 days in late December of 2006. The hydroacoustic signals were recorded by a hydrophone deployed near the source and at a sparse network of permanent hydrophone stations operated by the International Monitoring System (IMS), at distances up to 9600 km. Our purpose was to determine how well signal characteristics could be predicted by the World Ocean Atlas 2005 (WOA05) climatological database for sources within the Antarctic circumpolar current (ACC). Waveforms were examined in the 1–100 Hz frequency band, and it was found that for clear transmission paths, the shot signals exceeded the noise only at frequencies above 20–30 Hz. Comparisons of signal spectra for recordings near the source and at the IMS stations show that transmission loss is nearly uniform as a function of frequency. Where recorded signal-to-noise ratios are high, observed and predicted traveltimes and signal dispersion agree to within 2 s under the assumption that propagation is adiabatic and follows a geodesic path. The deflection of the transmission path by abrupt spatial variations in sound speed at the northern ACC boundary is predicted to decrease traveltimes to the IMS stations by several seconds, depending on the path. Acoustic velocities within the ACC are predicted to vary monthly, hence the accuracy of source location estimates based only on arrival times at IMS stations depends on the monthly or seasonal database used to predict traveltimes and on whether we account for path deflection. However, estimates of source locations within the ACC that are based only on observed waveforms at IMS hydrophones are highly dependent on the configuration of the IMS network; a set of shots observed only at an IMS station in the Indian Ocean and another in the South Pacific was located to within 10 km in longitude, but was poorly constrained in latitude. Several sets of shots observed only at IMS hydrophones in the Indian Ocean were ... Text Antarc* Antarctic Antarctica HighWire Press (Stanford University) Antarctic Indian New Zealand Pacific The Antarctic Geophysical Journal International 176 2 478 490 |
institution |
Open Polar |
collection |
HighWire Press (Stanford University) |
op_collection_id |
fthighwire |
language |
English |
topic |
Marine geoscience |
spellingShingle |
Marine geoscience De Groot-Hedlin, C. Blackman, Donna K. Jenkins, C. Scott Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean |
topic_facet |
Marine geoscience |
description |
A series of small depth charges was detonated along a transect from New Zealand to Antarctica over a period of 3 days in late December of 2006. The hydroacoustic signals were recorded by a hydrophone deployed near the source and at a sparse network of permanent hydrophone stations operated by the International Monitoring System (IMS), at distances up to 9600 km. Our purpose was to determine how well signal characteristics could be predicted by the World Ocean Atlas 2005 (WOA05) climatological database for sources within the Antarctic circumpolar current (ACC). Waveforms were examined in the 1–100 Hz frequency band, and it was found that for clear transmission paths, the shot signals exceeded the noise only at frequencies above 20–30 Hz. Comparisons of signal spectra for recordings near the source and at the IMS stations show that transmission loss is nearly uniform as a function of frequency. Where recorded signal-to-noise ratios are high, observed and predicted traveltimes and signal dispersion agree to within 2 s under the assumption that propagation is adiabatic and follows a geodesic path. The deflection of the transmission path by abrupt spatial variations in sound speed at the northern ACC boundary is predicted to decrease traveltimes to the IMS stations by several seconds, depending on the path. Acoustic velocities within the ACC are predicted to vary monthly, hence the accuracy of source location estimates based only on arrival times at IMS stations depends on the monthly or seasonal database used to predict traveltimes and on whether we account for path deflection. However, estimates of source locations within the ACC that are based only on observed waveforms at IMS hydrophones are highly dependent on the configuration of the IMS network; a set of shots observed only at an IMS station in the Indian Ocean and another in the South Pacific was located to within 10 km in longitude, but was poorly constrained in latitude. Several sets of shots observed only at IMS hydrophones in the Indian Ocean were ... |
format |
Text |
author |
De Groot-Hedlin, C. Blackman, Donna K. Jenkins, C. Scott |
author_facet |
De Groot-Hedlin, C. Blackman, Donna K. Jenkins, C. Scott |
author_sort |
De Groot-Hedlin, C. |
title |
Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean |
title_short |
Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean |
title_full |
Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean |
title_fullStr |
Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean |
title_full_unstemmed |
Effects of variability associated with the Antarctic circumpolar current on sound propagation in the ocean |
title_sort |
effects of variability associated with the antarctic circumpolar current on sound propagation in the ocean |
publisher |
Oxford University Press |
publishDate |
2009 |
url |
http://gji.oxfordjournals.org/cgi/content/short/176/2/478 https://doi.org/10.1111/j.1365-246X.2008.04007.x |
geographic |
Antarctic Indian New Zealand Pacific The Antarctic |
geographic_facet |
Antarctic Indian New Zealand Pacific The Antarctic |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_relation |
http://gji.oxfordjournals.org/cgi/content/short/176/2/478 http://dx.doi.org/10.1111/j.1365-246X.2008.04007.x |
op_rights |
Copyright (C) 2009, Oxford University Press |
op_doi |
https://doi.org/10.1111/j.1365-246X.2008.04007.x |
container_title |
Geophysical Journal International |
container_volume |
176 |
container_issue |
2 |
container_start_page |
478 |
op_container_end_page |
490 |
_version_ |
1766274659844620288 |