Howe Bruce M.

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Bruce M.

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The North Pacific Acoustic Laboratory deep-water acoustic propagation experiments in the Philippine Sea

(Acoustical Society of America, 2013-10) Worcester, Peter F. ; Dzieciuch, Matthew A. ; Mercer, James A. ; Andrew, Rex K. ; Dushaw, Brian D. ; Baggeroer, Arthur B. ; Heaney, Kevin D. ; D'Spain, Gerald L. ; Colosi, John A. ; Stephen, Ralph A. ; Kemp, John N. ; Howe, Bruce M. ; Van Uffelen, Lora J. ; Wage, Kathleen E.

A series of experiments conducted in the Philippine Sea during 2009–2011 investigated deep-water acoustic propagation and ambient noise in this oceanographically and geologically complex region: (i) the 2009 North Pacific Acoustic Laboratory (NPAL) Pilot Study/Engineering Test, (ii) the 2010–2011 NPAL Philippine Sea Experiment, and (iii) the Ocean Bottom Seismometer Augmentation of the 2010–2011 NPAL Philippine Sea Experiment. The experimental goals included (a) understanding the impacts of fronts, eddies, and internal tides on acoustic propagation, (b) determining whether acoustic methods, together with other measurements and ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions, (c) improving our understanding of the physics of scattering by internal waves and spice, (d) characterizing the depth dependence and temporal variability of ambient noise, and (e) understanding the relationship between the acoustic field in the water column and the seismic field in the seafloor. In these experiments, moored and ship-suspended low-frequency acoustic sources transmitted to a newly developed distributed vertical line array receiver capable of spanning the water column in the deep ocean. The acoustic transmissions and ambient noise were also recorded by a towed hydrophone array, by acoustic Seagliders, and by ocean bottom seismometers.
Modal analysis of the range evolution of broadband wavefields in the North Pacific Ocean : low mode numbers

(Acoustical Society of America, 2012-06) Udovydchenkov, Ilya A. ; Brown, Michael G. ; Duda, Timothy F. ; Mercer, James A. ; Andrew, Rex K. ; Worcester, Peter F. ; Dzieciuch, Matthew A. ; Howe, Bruce M. ; Colosi, John A.

The results of mode-processing measurements of broadband acoustic wavefields made in the fall of 2004 as part of the Long-Range Ocean Acoustic Propagation Experiment (LOAPEX) in the eastern North Pacific Ocean are reported here. Transient wavefields in the 50–90 Hz band that were recorded on a 1400 -m long 40 element vertical array centered near the sound channel axis are analyzed. This array was designed to resolve low-order modes. The wavefields were excited by a ship-suspended source at seven ranges, between approximately 50 and 3200 km, from the receiving array. The range evolution of broadband modal arrival patterns corresponding to fixed mode numbers (“modal group arrivals”) is analyzed with an emphasis on the second (variance) and third (skewness) moments. A theory of modal group time spreads is described, emphasizing complexities associated with energy scattering among low-order modes. The temporal structure of measured modal group arrivals is compared to theoretical predictions and numerical simulations. Theory, simulations, and observations generally agree. In cases where disagreement is observed, the reasons for the disagreement are discussed in terms of the underlying physical processes and data limitations.
Weakly dispersive modal pulse propagation in the North Pacific Ocean

(Acoustical Society of America, 2013-10) Udovydchenkov, Ilya A. ; Brown, Michael G. ; Duda, Timothy F. ; Worcester, Peter F. ; Dzieciuch, Matthew A. ; Mercer, James A. ; Andrew, Rex K. ; Howe, Bruce M. ; Colosi, John A.

The propagation of weakly dispersive modal pulses is investigated using data collected during the 2004 long-range ocean acoustic propagation experiment (LOAPEX). Weakly dispersive modal pulses are characterized by weak dispersion- and scattering-induced pulse broadening; such modal pulses experience minimal propagation-induced distortion and are thus well suited to communications applications. In the LOAPEX environment modes 1, 2, and 3 are approximately weakly dispersive. Using LOAPEX observations it is shown that, by extracting the energy carried by a weakly dispersive modal pulse, a transmitted communications signal can be recovered without performing channel equalization at ranges as long as 500 km; at that range a majority of mode 1 receptions have bit error rates (BERs) less than 10%, and 6.5% of mode 1 receptions have no errors. BERs are estimated for low order modes and compared with measurements of signal-to-noise ratio (SNR) and modal pulse spread. Generally, it is observed that larger modal pulse spread and lower SNR result in larger BERs.
Deep seafloor arrivals : an unexplained set of arrivals in long-range ocean acoustic propagation

(Acoustical Society of America, 2009-08) Stephen, Ralph A. ; Bolmer, S. Thompson ; Dzieciuch, Matthew A. ; Worcester, Peter F. ; Andrew, Rex K. ; Buck, Linda J. ; Mercer, James A. ; Colosi, John A. ; Howe, Bruce M.

Receptions, from a ship-suspended source (in the band 50–100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), “deep seafloor arrivals,” that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves.
The Deep Ocean Observing Strategy: addressing global challenges in the deep sea through collaboration

(Marine Technology Society, 2022-06-08) Smith, Leslie M. ; Cimoli, Laura ; LaScala-Gruenewald, Diana ; Pachiadaki, Maria G. ; Phillips, Brennan T. ; Pillar, Helen R. ; Stopa, Justin ; Baumann-Pickering, Simone ; Beaulieu, Stace E. ; Bell, Katherine L. C. ; Harden-Davies, Harriet ; Gjerde, Kristina M. ; Heimbach, Patrick ; Howe, Bruce M. ; Janssen, Felix ; Levin, Lisa A. ; Ruhl, Henry A. ; Soule, S. Adam ; Stocks, Karen ; Vardaro, Michael F. ; Wright, Dawn J.

The Deep Ocean Observing Strategy (DOOS) is an international, community-driven initiative that facilitates collaboration across disciplines and fields, elevates a diverse cohort of early career researchers into future leaders, and connects scientific advancements to societal needs. DOOS represents a global network of deep-ocean observing, mapping, and modeling experts, focusing community efforts in the support of strong science, policy, and planning for sustainable oceans. Its initiatives work to propose deep-sea Essential Ocean Variables; assess technology development; develop shared best practices, standards, and cross-calibration procedures; and transfer knowledge to policy makers and deep-ocean stakeholders. Several of these efforts align with the vision of the UN Ocean Decade to generate the science we need to create the deep ocean we want. DOOS works toward (1) a healthy and resilient deep ocean by informing science-based conservation actions, including optimizing data delivery, creating habitat and ecological maps of critical areas, and developing regional demonstration projects; (2) a predicted deep ocean by strengthening collaborations within the modeling community, determining needs for interdisciplinary modeling and observing system assessment in the deep ocean; (3) an accessible deep ocean by enhancing open access to innovative low-cost sensors and open-source plans, making deep-ocean data Findable, Accessible, Interoperable, and Reusable, and focusing on capacity development in developing countries; and finally (4) an inspiring and engaging deep ocean by translating science to stakeholders/end users and informing policy and management decisions, including in international waters.
Analysis of Deep Seafloor Arrivals observed on NPAL04

(Woods Hole Oceanographic Institution, 2012-12) Stephen, Ralph A. ; Bolmer, S. Thompson ; Udovydchenkov, Ilya A. ; Dzieciuch, Matthew A. ; Worcester, Peter F. ; Andrew, Rex K. ; Mercer, James A. ; Colosi, John A. ; Howe, Bruce M.

This report gives an overview of the analysis that was done on Deep Seafloor Arrivals since they were initially presented in Stephen et al (2009). All of the NPAL04/LOAPEX (North Pacific Acoustic Laboratory, 2004/ Long Range Ocean Acoustic Propagation Experiment) data on three ocean bottom seismometers (OBSs) at ~5,000m depth and the deepest element of the deep vertical line array (DVLA) at 4250m depth has been analyzed. A distinctive pattern of late arrivals was observed on the three OBSs for transmissions from T500 to T2300. The delays of these arrivals with respect to the parabolic equation predicted (PEP) path were the same for all ranges from 500 to 2300km, indicating that the delay was introduced near the receivers. At 500km range the same arrival was observed throughout the water column on the DVLA. We show that arrivals in this pattern converted from a PEP path to a bottom-diffracted surface reflected (BDSR) path at an off-geodesic seamount.
Bottom interacting sound at 50 km range in a deep ocean environment

(Acoustical Society of America, 2012-10) Udovydchenkov, Ilya A. ; Stephen, Ralph A. ; Duda, Timothy F. ; Bolmer, S. Thompson ; Worcester, Peter F. ; Dzieciuch, Matthew A. ; Mercer, James A. ; Andrew, Rex K. ; Howe, Bruce M.

Data collected during the 2004 Long-range Ocean Acoustic Propagation Experiment provide absolute intensities and travel times of acoustic pulses at ranges varying from 50 to 3200 km. In this paper a subset of these data is analyzed, focusing on the effects of seafloor reflections at the shortest transmission range of approximately 50 km. At this range bottom-reflected (BR) and surface-reflected, bottom-reflected energy interferes with refracted arrivals. For a finite vertical receiving array spanning the sound channel axis, a high mode number energy in the BR arrivals aliases into low mode numbers because of the vertical spacing between hydrophones. Therefore, knowledge of the BR paths is necessary to fully understand even low mode number processes. Acoustic modeling using the parabolic equation method shows that inclusion of range-dependent bathymetry is necessary to get an acceptable model-data fit. The bottom is modeled as a fluid layer without rigidity, without three dimensional effects, and without scattering from wavelength-scale features. Nonetheless, a good model-data fit is obtained for sub-bottom properties estimated from the data.
Global observing needs in the deep ocean

(Frontiers Media, 2019-03-29) Levin, Lisa A. ; Bett, Brian J. ; Gates, Andrew R. ; Heimbach, Patrick ; Howe, Bruce M. ; Janssen, Felix ; McCurdy, Andrea ; Ruhl, Henry A. ; Snelgrove, Paul V. R. ; Stocks, Karen ; Bailey, David ; Baumann-Pickering, Simone ; Beaverson, Chris ; Benfield, Mark C. ; Booth, David J. ; Carreiro-Silva, Marina ; Colaço, Ana ; Eblé, Marie C. ; Fowler, Ashley M. ; Gjerde, Kristina M. ; Jones, Daniel O. B. ; Katsumata, Katsuro ; Kelley, Deborah S. ; Le Bris, Nadine ; Leonardi, Alan P. ; Lejzerowicz, Franck ; Macreadie, Peter I. ; McLean, Dianne ; Meitz, Fred ; Morato, Telmo ; Netburn, Amanda ; Pawlowski, Jan ; Smith, Craig R. ; Sun, Song ; Uchida, Hiroshi ; Vardaro, Michael F. ; Venkatesan, Ramasamy ; Weller, Robert A.

The deep ocean below 200 m water depth is the least observed, but largest habitat on our planet by volume and area. Over 150 years of exploration has revealed that this dynamic system provides critical climate regulation, houses a wealth of energy, mineral, and biological resources, and represents a vast repository of biological diversity. A long history of deep-ocean exploration and observation led to the initial concept for the Deep-Ocean Observing Strategy (DOOS), under the auspices of the Global Ocean Observing System (GOOS). Here we discuss the scientific need for globally integrated deep-ocean observing, its status, and the key scientific questions and societal mandates driving observing requirements over the next decade. We consider the Essential Ocean Variables (EOVs) needed to address deep-ocean challenges within the physical, biogeochemical, and biological/ecosystem sciences according to the Framework for Ocean Observing (FOO), and map these onto scientific questions. Opportunities for new and expanded synergies among deep-ocean stakeholders are discussed, including academic-industry partnerships with the oil and gas, mining, cable and fishing industries, the ocean exploration and mapping community, and biodiversity conservation initiatives. Future deep-ocean observing will benefit from the greater integration across traditional disciplines and sectors, achieved through demonstration projects and facilitated reuse and repurposing of existing deep-sea data efforts. We highlight examples of existing and emerging deep-sea methods and technologies, noting key challenges associated with data volume, preservation, standardization, and accessibility. Emerging technologies relevant to deep-ocean sustainability and the blue economy include novel genomics approaches, imaging technologies, and ultra-deep hydrographic measurements. Capacity building will be necessary to integrate capabilities into programs and projects at a global scale. Progress can be facilitated by Open Science and Findable, Accessible, Interoperable, Reusable (FAIR) data principles and converge on agreed to data standards, practices, vocabularies, and registries. We envision expansion of the deep-ocean observing community to embrace the participation of academia, industry, NGOs, national governments, international governmental organizations, and the public at large in order to unlock critical knowledge contained in the deep ocean over coming decades, and to realize the mutual benefits of thoughtful deep-ocean observing for all elements of a sustainable ocean.
Deep seafloor arrivals in long range ocean acoustic propagation

(Acoustical Society of America, 2013-10) Stephen, Ralph A. ; Bolmer, S. Thompson ; Udovydchenkov, Ilya A. ; Worcester, Peter F. ; Dzieciuch, Matthew A. ; Andrew, Rex K. ; Mercer, James A. ; Colosi, John A. ; Howe, Bruce M.

Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These “deep seafloor” arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200 km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100 m depth and is about 18 km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35 dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200 km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor.
A test of basin-scale acoustic thermometry using a large-aperture vertical array at 3250-km range in the eastern North Pacific Ocean

(Acoustical Society of America, 1999-06) Worcester, Peter F. ; Cornuelle, Bruce D. ; Dzieciuch, Matthew A. ; Munk, Walter H. ; Howe, Bruce M. ; Mercer, James A. ; Spindel, Robert C. ; Colosi, John A. ; Metzger, Kurt ; Birdsall, Theodore G. ; Baggeroer, Arthur B.

Broadband acoustic signals were transmitted during November 1994 from a 75-Hz source suspended near the depth of the sound-channel axis to a 700-m long vertical receiving array approximately 3250 km distant in the eastern North Pacific Ocean. The early part of the arrival pattern consists of raylike wave fronts that are resolvable, identifiable, and stable. The later part of the arrival pattern does not contain identifiable raylike arrivals, due to scattering from internal-wave-induced sound-speed fluctuations. The observed ray travel times differ from ray predictions based on the sound-speed field constructed using nearly concurrent temperature and salinity measurements by more than a priori variability estimates, suggesting that the equation used to compute sound speed requires refinement. The range-averaged oceansound speed can be determined with an uncertainty of about 0.05 m/s from the observed ray travel times together with the time at which the near-axial acoustic reception ends, used as a surrogate for the group delay of adiabatic mode 1. The change in temperature over six days can be estimated with an uncertainty of about 0.006 °C. The sensitivity of the travel times to ocean variability is concentrated near the ocean surface and at the corresponding conjugate depths, because all of the resolved ray arrivals have upper turning depths within a few hundred meters of the surface.
NPAL04 OBS data analysis part 1 : kinematics of deep seafloor arrivals

(Woods Hole Oceanographic Institution, 2008-12) Stephen, Ralph A. ; Bolmer, S. Thompson ; Udovydchenkov, Ilya A. ; Worcester, Peter F. ; Dzieciuch, Matthew A. ; Van Uffelen, Lora J. ; Mercer, James A. ; Andrew, Rex K. ; Buck, Linda J. ; Colosi, John A. ; Howe, Bruce M.

These notes provide supporting information for a JASA (Journal of the Acoustical Society of America) LttE (Letter to the Editor) manuscript, "Deep seafloor arrivals: A new class of arrivals in long-range ocean acoustic propagation" (Stephen et al., submitted). It addresses five issues raised by the co-authors: 1) incorrect processing for the time-compressed traces at T2300 and T3200 that appeared in an early version of the LttE (T2300, T3200 … refer to transmissions at 2300, 3200km etc from the DVLA (Deep Vertical Line Array)), 2) processing issues, including the trade-offs between coherent and incoherent stacking and corrections for the effects of moving sources and receivers and tidal currents (Doppler), 4) the distinction between "deep shadow zone arrivals", which occur below the turning points in Parabolic Equation (PE) models, and "deep seafloor arrivals", which appear dominantly on the Ocean Bottom Seismometer (OBS) but are either very weak or absent on the deepest element in the DVLA and do not coincide with turning points in the PE model (some of these OBS late arrivals occur after the finale region), 4) the role of surface-reflected bottomreflected (SRBR) paths in explaining the late arriving energy, and 5) generally reconciling the OBS analysis with work by other North Pacific Acoustic Laboratory (NPAL) investigators and Dushaw et al (1999).

Howe Bruce M.

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