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  • 1
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    Global Observing Needs in the Deep Ocean (2019)
    In:  EPIC3Frontiers in Marine Science, 6, ISSN: 2296-7745
    Details
    Publication Date: 2019-06-03
    Description: 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 2
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    Evolving approaches for deep-ocean biology and ecosystems observations in the Global Ocean Observing System (2019)
    In:  EPIC3OceanObs'19 conference, Honolulu, Hawaii, USA, 2019-09-16-2019-09-20
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    Publication Date: 2019-12-13
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Essential Ocean Variables for Biogeochemical Observations (2019)
    In:  EPIC3OceanObs'19 conference, Honolulu, Hawaii, USA, 2019-09-16-2019-09-20
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    Publication Date: 2020-02-04
    Description: Ocean biogeochemical (BGC) processes are fundamental for several key ocean ecosystem functions and services. For example, carbon dioxide uptake and storage by chemical uptake and biological fixation in combination with transport to depth remove anthropogenic carbon from the atmosphere and counteract global warming. Another important example would be nutrient regeneration from organic matter remineralization that sustains ocean productivity and, hence, also seafood supply. Although many BGC processes are rooted in surface waters where primary productivity and ocean / atmosphere exchange takes place, the deep ocean contributes strongly to the cycling and sequestration of elements. Without a consideration of organic particle attenuation in the deep pelagic and rates of remineralization and accumulation at the vast deep seafloor, the efficiency of the biological carbon pump and the recycling of nutrients – and potential effects of global change – can hardly be quantified. Considering the relevance of the deep ocean, the Deep Ocean Observing Strategy ‘DOOS’ is revising the Essential Ocean Variables (EOVs) specified by the Global Ocean Observing System (GOOS) with a deep ocean perspective. The DOOS community recognized, that most GOOS BGC EOVs are also relevant for deep ocean observations. However, the bottom of the sea requires more attention to assess its contribution to ocean BGC. ‘Seafloor labile organic matter’ and ‘seafloor respiration’ are candidates for additional EOVs beyond the GOOS EOVs ‘oxygen’ and ‘particulate matter’. Online questionnaires are prepared to facilitate an expert revision of GOOS BGC EOVs in order to make specific suggestions for modifications to the responsible GOOS panel. The revision includes the target phenomena and spatiotemporal scales, the observing platforms and networks considered relevant, and the requirements of observations. This contribution introduces the revision approach and invites experts to take part.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Modal analysis of the range evolution of broadband wavefields in the North Pacific Ocean : low mode numbers (2012)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 4409-4427, doi:10.1121/1.4707431.
    Description: 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.
    Description: This work was supported by the Office of Naval Research, Code 322, Grant Nos. N00014-08-1-0195, N00014-06-1-0245, and N0014-11-1-0194.
    Keywords: Acoustic field ; Underwater acoustic propagation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    A test of basin-scale acoustic thermometry using a large-aperture vertical array at 3250-km range in the eastern North Pacific Ocean (2014)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1999. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 105 (1999): 3185, doi:10.1121/1.424649.
    Description: 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.
    Description: This work was supported largely by the Strategic Environmental Research and Development Program through Defense Advanced Research Projects Agency ~DARPA! Grant No. MDA972-93- 1-0003. Additional support was provided at SIO by the Office of Naval Research ~ONR! through Grant No. N00014- 97-1-0258. J. Colosi wishes to acknowledge support from an ONR Young Investigator Award, from the J. Lamar Worzel Assistant Scientist Fund, and from the Penzance Endowed Fund in support of scientific staff at WHOI.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
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    Deep seafloor arrivals : an unexplained set of arrivals in long-range ocean acoustic propagation (2009)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2009. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 126 (2009): 599-606, doi:10.1121/1.3158826.
    Description: 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.
    Description: The LOAPEX source deployments, the moored DVLA receiver deployments, and some post-cruise data reduction and analysis were funded by the Office of Naval Research under Award Nos. N00014-1403-1-0181, N00014-03-1-0182, and N00014-06-1-0222. Additional post-cruise analysis support was provided to RAS through the Edward W. and Betty J. Scripps Chair for Excellence in Oceanography. The OBS/Hs used in the experiment were provided by Scripps Institution of Oceanography under the U.S. National Ocean Bottom Seismic Instrumentation Pool (SIO-OBSIP—http://www.obsip.org). To cover the costs of the OBS/H deployments funds were paid to SIO-OBSIP from the National Science Foundation and from the Woods Hole Oceanographic Institution Deep Ocean Exploration Institute.
    Keywords: Hydrophones ; Ocean waves ; Oceanographic equipment ; Sonar ; Underwater acoustic propagation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Deep seafloor arrivals in long range ocean acoustic propagation (2013)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2013. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 134 (2013): 3307-3317, doi:10.1121/1.4818845.
    Description: 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.
    Description: The OBS/Hs used in the LOAPEX field program were provided by Scripps Institution of Oceanography under the U.S. National Ocean Bottom Seismic Instrumentation Pool (SIO-OBSIP, http:// www.obsip.org). The OBS/H deployments themselves were co-funded through direct funding to SIO-OBSIP by the National Science Foundation and by Woods Hole Oceanographic Institution under a grant from the WHOI Deep Ocean Exploration Institute. The LOAPEX source deployments and the moored DVLA receiver deployments were funded by the Office of Naval Research under Award Nos. N00014-03-1-0181 and N00014-03-1-0182. The data reduction and analysis in this paper were funded by the Office of Naval Research under Award Nos. N00014-06-1-0222 and N00014-10-1-0510. Additional post-cruise analysis support was provided to RAS through the Edward W. and Betty J. Scripps Chair for Excellence in Oceanography.
    Keywords: Acoustic arrays ; Acoustic noise ; Acoustic signal processing ; Acoustic wave reflection ; Acoustic wave velocity ; Long-range order ; Ocean waves ; Seafloor phenomena ; Seismometers ; Surface acoustic waves ; Surface energy ; Underwater acoustic propagation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Weakly dispersive modal pulse propagation in the North Pacific Ocean (2013)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2013. This article is posted here by permission of Acoustical Society of America or personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 134 (2013): 3386, doi:10.1121/1.4820882.
    Description: 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.
    Description: This work was supported by the Office of Naval Research, Code 322, Grant Nos. N00014-06-1-0245, N00014-08-1-0195, and N00014-11-1-0194.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
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    Bottom interacting sound at 50 km range in a deep ocean environment (2012)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 132 (2012): 2224-2231, doi:10.1121/1.4747617.
    Description: 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.
    Description: This work was supported by the Office of Naval Research, Code 322, Grant Nos. N00014- 10-1-0987, N00014-11-1-0194, and N00014-10-1-0510.
    Keywords: Acoustic wave reflection ; Acoustic wave scattering ; Acoustic wave transmission ; Bathymetry ; Parabolic equations ; Uunderwater acoustic propagation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
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    NPAL04 OBS data analysis part 1 : kinematics of deep seafloor arrivals (2009)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-26
    Description: 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).
    Description: Funding was provided by the Office of Naval Research through Contract No. N00014-06-1-0222.
    Keywords: Ocean bottom seismology ; Ocean acoustic propagation ; Bottom interaction
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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