I was an oceanographer at the
Applied Physics Laboratory, University of Washington from 1992-2016,.
and an an affiliate assistant/associate professor of Oceanography at the
School of Oceanography, UW from 1999—2015.
My interests are in the application of long-range acoustic transmissions for ocean
observation - also known as ocean acoustic tomography. An essential aspect of tomography is to
understand the acoustic forward problem, so a closely related interest is understanding the
nature of long-range acoustic propagation in the ocean.
Tomography is a technique that has matured; it
offers excellent signal-to-noise capability for observing variability at the largest oceanic scales. Three
applications I am actively pursuing are: measuring the large-scale variations of heat content in
ocean basins, estimation of the radiation of low-mode internal tides from topographic features and the
apparent predictability of that radiation in the ordinary tidal sense, and measuring the heat and heat transport
through Fram Strait to high precision. Other interests are modeling and data assimilation (and how tomography
may be used in models), and the effective use of parallel computational techniques (SMP machines, cluster of PCs,
graphics cards/CUDA) in scientific analysis.
Recent Tomography Advocacy/Conference Papers (2016-2017)
Dushaw, B., 2016. Ocean acoustic tomography: A missing element of the ocean observing system, in Proceedings Institute of Acoustics, Conference, Acoustic & Environmental Variability, Fluctuations and Coherence, Cambridge, U.K., 12-13 December 2016, 5 pp. Article
Dushaw, B., J. Colosi, T. Duda, M. Dzieciuch, B. Howe, A. Kaneko, H. Sagen, E. Skarsoulis, and X. Zhu, 2017. Ocean acoustic tomography: A missing contribution to the Ocean Observing System, in Proceedings Underwater Acoustics Conference and Exhibition 2017, Skiathos Island, Greece, 3-8 September 2017, 12 pp. Article
Dushaw, B., 2017. Acoustic tomography as a component the Atlantic Ocean Observing System: Opportunities and Challenges, in Proceedings 8th EuroGOOS Conference, Bergen, Norway, 3-5 October 2017, 5 pp. Article
Dushaw, B., 2017. Ocean Observing Systems and Ocean Observatories, Oceanographers and Acousticians - A Personal Perspective, in Applied Underwater Acoustics, L. Bjørnø (T. Neighbors, D. Bradley, Eds.) Amsterdam, Netherlands: Elsevier, 964 pp., ISBN: 978-0-12-811240-3, pp. 931-934. Article
The Fram Strait Papers (2016-2017)
Dushaw, B. D., H. Sagen and A. Beszczynska-Möller, 2016. Sound speed as a proxy variable to
temperature in Fram Strait, J. Acoust. Soc. Am., 140, 622-630. doi: 10.1121/1.4959000
Dushaw, B. D., and H. Sagen, 2016. A comparative study of moored/point and acoustic tomography/integral observations of sound speed in Fram Strait using objective mapping techniques, J.
Atmos. Oceanic Tech., 33, 2079-2093. doi: 10.1175/JTECH-D-15-0251.1
Dushaw, B. D., H. Sagen, and A. Beszczynska-Möller, 2016. On the effects of small-scale variability on acoustic propagation in Fram Strait: The tomography forward problem, J. Acoust.
Soc. Am., 140, 1286-1299. doi: 10.1121/1.4961207
Sagen, H., B. D. Dushaw, E. K. Skarsoulis, D. Dumont, M. A. Dzieciuch, and A.
Beszczynska-Möller, 2016. Time series of temperature in Fram Strait determined
from the 2008-2009 DAMOCLES acoustic tomography measurements and an ocean
model, J. Geophys. Res., 121, doi: 10.1002/2015JC011591.
Sagen, H., F. Geyer, S. Sandven, M. Babiker, B. D. Dushaw, P. F. Worcester, M. A. Dzieciuch, B. Cornuelle, A. Beszczynska-Möller, 2017. Resolution, identification, and stability of broadband acoustic arrivals in Fram Strait, J. Acoust. Soc. Am., 141, 2055-2068, doi: 10.1121/1.4978780
Dushaw, B. D., H. Sagen, 2017. The role of simulated small-scale ocean variability in inverse
computations for ocean acoustic tomography, J. Acoust. Soc. Am., submitted.
Encyclopedia Article. An encyclopedia article on ocean
acoustic tomography. The citation is:
Dushaw, B. D.,
2013. ‘‘Ocean Acoustic Tomography’’
in Encyclopedia of Remote Sensing, E. G. Njoku, Ed.,
Springer, Springer-Verlag Berlin Heidelberg, 2013. doi: 10.1007/SpringerReference_331410
Acoustic Reverberation From an Atomic Test. I took another look at the acoustic signals generated by the 1955 atomic test "WIGWAM"
in the eastern North Pacific. The sound pulse illuminated the entire North and South Pacific
basins and was reflected back to California and Hawaii to be recorded as hours-long coda. A quite
simple analysis produced this paper with
Dushaw, B. D.,
2015. WIGWAM reverberation revisited, Bulletin
Seismological Soc. Am., 105,
The electronic supplemenatary material for the paper can be seen on the BSSA website, or on this
I presented these results at the UACE2017 conference. The conference paper gives a discussion
on why and how I came to work on this problem:
Dushaw, B., 2017. WIGWAM Reverberation Revisited, in Proceedings Underwater Acoustics Conference and Exhibition 2017, Skiathos Island, Greece, 3-8 September 2017, 5 pp. Article
Antipodal Acoustic Thermometry. The culmination of quite a
lot of numerical and historical research, we used
acoustic signals from an antipodal acoustic propagation experiment in 1960 to
make an estimate of the change in ocean temperature from 1960 to 2004, averaged
along the sound channel axis. The signals traveled from Perth, Australia to
Bermuda. The measurements in 1960 were established to have
a meaningful accuracy, and equivalent signals were computed using numerical
ocean state estimates for 2004. No change in travel time (hence no change in
temperature from 1960 to 2004) was observed. While error bars were large, they
were not particularly larger than other measurement types. The computation
establishes acoustic thermometry as both a viable and important measurement
type, complementary to other measurement types. The
lengthy publication is open access.
Dushaw, B. D., and D. Menemenlis,
2014. Antipodal acoustic thermometry: 1960, 2004,
Deep-Sea Res. I,
86, 1−20. doi: 10.1016/j.dsr.2013.12.008
Dushaw, B. D., 2008. Another look
at the 1960 Perth to Bermuda long-range acoustic propagation experiment,
Geophys. Res. Lett., 35 , doi: 10.1029/2008GL033415.
Global Predictability of Mode-1 Internal Tides. This year (2015) marks the 20th anniversary
of a paper published in 1995 reporting on the radiation of mode-1 internal tides from Hawaii far into the ocean's
interior as measured by acoustic tomography. This radiation was confirmed a year later by observations by the
TOPEX/POSEIDON satelite altimeter. I have worked on these observations, on and off, over this 20 year period. This
work eventually led to the conclusion that these internal tide waves are so coherent that their amplitude and
phase are in fact predictable, much like the barotropic tide. A detailed and thorough analysis of both
tomography and satelite altimetry data demonstrating this predictability appeared in a
publication in the journal Deep-Sea Research
in 2011. While the practical value of this discovery is to be determined, the discovery is somewhat revolutionary
in that it overturns firmly held views by physical oceanographers about the incoherence of ocean variability.
With support from the National Aeronautics and Space Administration, his work has
been extended and refined to develop a global model that can be used to predict
the tidal amplitude and
phase of mode-1 internal tides anywhere in the world's oceans. The model predicts the in situ observations by
acoustic tomography from the Philippine to Sargasso Seas. The animation below gives the mode-1 internal tide
amplitude for the M2 frequency; the model includes the six major tidal constituents and modes 1
The 114 pp. report describing this model can be accessed
HERE (v1.1) (19 MB). The use of acoustic
tomography and satelite altimetry illustrates the complementary nature of these data types – altimetry
shows the spatial coherence of these internal tides, while tomography shows the temporal coherence.
(NEW - 11/10/2015) This model, together with software and documentation to enable computation of tidal predictions
or plotting of maps, can be downloaded from HERE (APL
site - See Supplemental Materials. A tarball of 2.4 GB in size contains the model and other aspects of the solution.) Unpacking this tarball
gives the empirical model and associated software that can be used for predicting mode-1 internal tides.
The tarball also disseminates the tomography and thermistor observations (time series of mode-1 amplitude derived
using acoustic tomography or thermistor data), animations of mode-1 internal tides the world over, and mode-1
properties derived from climatology that allow the mode-1 solutions for SSH to be extended into the ocean's
interior (mode amplitude, current, displacement, etc.).
The citations for the 2011 publication and this Technical Memorandum are:
Dushaw, B. D., P. F. Worcester, and
M. A. Dzieciuch, 2011. On the predictability of mode-1 internal tides,
Deep-Sea Res. I, 58, 677−698. doi: 10.1016/j.dsr.2011.04.002
Dushaw, B., 2015. An Empirical Model for Mode-1 Internal Tides Derived from Satellite
Altimetry: Computing Accurate Tidal Predictions at Arbitrary Points over
the World Oceans, Technical Memorandum APL-UW TM 1-15, 114 pp.
Click on the image to view a large-scale animation of M2 mode-1
amplitude (not SSH) (27 MB).
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