Naval Oceanography Office

We report the results of a study correlating mid-frequency transmission loss (TL) measurements with properties of nearby sediment core samples. A large number of measurements were made in shallow water areas with water depths ranging from 50 to 160 m. The statistical distributions of the derived bottom-loss values are found to be nearly invariant to various sediment properties derived from the corresponding core samples. These properties include seafloor sound speed, density, and porosity as well as a number of others. It is shown from Parabolic Equation model calculations that use Hamilton’s values for the different sediment types [J. Acoust. Soc. Am. 68, 1313 (1980)] that the TL can vary by 15 dB or more at a range of 20 km. Therefore the absence of substantial bias in the data with respect to sediment types is somewhat surprising and worth investigation. The possible explanations, such as high spatial variability of seafloor processes including presence of ripples, gas, and other causes are being investigated and will be discussed. [Approved for public release].

The research in this paper focuses on the I/O problem associated with a parallel application writing to a single physical disk. Included in our research are the original ideas that led to the first version of the parallel software, subsequent versions of the software derived from lessons learned from benchmark results, and speedup results of each version. The underlying purpose of this software is to process hydrographic data having a complicated, multi-tiered format. The data processing involves reading tens to hundreds of files containing raw data, filtering out extraneous data values, and writing the filtered data to a single file used in additional processing. The problem is not computationally intensive, but bound by the system's file writing capability. Results show that the more responsible the software was for organizing the data before writing, the better the speedup. The critical factor for writing data efficiently involved the limitation of writing data over a single I/O controller. Our parallel software has fantastic utility where system specifications do not allow for the use of parallel file systems, or writing data over multiple I/O controllers.

Abstract The Naval Oceanographic Office's (NAVOCEANO's) mission is to collect, process, and distribute products and data to the Department of Defense (DOD) and other national and international customers. In the past several years, NAVOCEANO has significantly increased capabilities to carry out this mission. First, the introduction of the Integrated Data Base Management System (IDBMS) in 1994 has provided management of over 150 years of irreplaceable ocean data. Second, when NAVOCEANO was designated one of four DOD Major Shared Resource Centers in 1995, a High Performance Computing Center was established. Third, the introduction of the T-AGS 60 PATHFINDER class multipurpose oceanographic survey ships in 1996 has allowed "one-stop shopping" in the coastal and deep waters of the world, on-board data processing, and highspeed data transmissions for rapid characterization of the marine environment. Independently, these three changes represent major milestones to support NAVOCEANO into the next century. The variety of advanced tools and equipment gives the hydrographer a much greater data collection and end-product capability. This paper will discuss past methodologies and the much-improved present capabilities, survey systems, and resulting products. It will also highlight the innovative and advanced technological developments NAVOCEANO is planning to enable us to meet our future challenges. Introduction For 165 years, the Naval Oceanographic Office (NAVOCEANO) has relied on new technologies to improve data collection, processing, and production capabilities. Today's new technologies allow a quantum leap in improving capabilities in all three areas. Described here are the most significant technological changes being implemented at NAVOCEANO today and in the near future and how they help us to provide the best data, best products, and best services to our customer - the Fleet. Background A key ingredient to the success of a warfighter's mission is the availability of timely, accurate meteorological and oceanographic (METOC) data or products. This is more true than ever in the highly variable shallow water in which today's Navy operates where climatology just will not do. We are challenged by the technological demands of sophisticated weapons systems and new operating areas that stress the capabilities of our existing systems. We have met these challenges by creative use of information technology. NAVOCEANO's mission includes collection and processing of METOC data, and the creation of tailored products to support the warfighter's mission. In today's world, the warfighter needs higher resolution data of the best quality - a lot more of it than in the past - as near real-time as possible. The old technologies - data collection at sea, lengthy transit to a shore analysis site, followed by long analysis and finally resulting in hardcopy reports delivered by mail - can no longer meet today's needs. We must embrace new technologies that allow us to collect high-resolution digital data, quality control it during or immediately after collection, compress the analysis time, and create new and different products for digital transmission to warfighters and the METOC centers that support them [1].

For the first time on a continent‐wide scale, scientists have applied new airborne remote‐sensing techniques that push beyond long‐standing limits to geophysical, geodetic, and glaciological studies. In the process, they have delineated several major crustal boundaries beneath the Greenland ice cap and possibly traced the path of the Iceland hot‐spot across central Greenland (see Figure 1). They have also greatly improved the geoid, or gravity reference surface of the Earth, for the region; provided ground truth for satellite altimeter studies; and established a baseline for determining the growth or shrinkage of one of the world's major ice sheets. The data will aid understanding in areas ranging from the geologic structure of Greenland to global climate change.

This paper presents a method for using surface loss as a function of angle in a parabolic-equation (PE) model. In this method, the complex pressure field in a layer near the surface is transformed to vertical wavenumber space where a loss function is applied. The field is then transformed back to depth space and merged with the field outside the layer in preparation for the next range step in the PE model. Test cases show the method to be computationally efficient as well as accurate.

The effect of a finite fetch on the acoustic field scattered by the ocean wind‐driven surface for various wind speeds is analyzed through numerical simulation. The JONSWAP spectrum is adopted to describe the surface statistics of growing seas and the Pierson‐Moskowitz spectrum for fully developed seas. Ensembles of three‐dimensional surfaces having the desired directional spectra are numerically generated. For each surface realization, the complex pressure of the forward scattered field is calculated within the framework of the Helmholtz‐Kirchhoff theory for kr > 1. Statistical moments of the scattered field are then calculated as ensemble averages. The fields scattered in the windward and cross‐wind directions are evaluted for frequencies up to 1.5 kHz and for angles away from grazing incidence. Results indicate that the scattered field is sensitive to the difference between the JONSWAP and the Pierson‐Moskowitz spectra. In particular, the total intensity and the coherence of the scattered field are sign...

Research Article| March 01, 1986 Are oceanic fracture zones locked and strong or weak?: New evidence for volcanic activity and weakness Allen Lowrie; Allen Lowrie 1Ocean Projects Division, NAVOCEANO, NASA Space Technology Laboratory Station, Mississippi 39529 Search for other works by this author on: GSW Google Scholar Christian Smoot; Christian Smoot 2Bathymetry Division, NAVOCEANO, NASA Space Technology Laboratory Station, Mississippi 39529 Search for other works by this author on: GSW Google Scholar Rodey Batiza Rodey Batiza 3Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130 Search for other works by this author on: GSW Google Scholar Author and Article Information Allen Lowrie 1Ocean Projects Division, NAVOCEANO, NASA Space Technology Laboratory Station, Mississippi 39529 Christian Smoot 2Bathymetry Division, NAVOCEANO, NASA Space Technology Laboratory Station, Mississippi 39529 Rodey Batiza 3Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1986) 14 (3): 242–245. https://doi.org/10.1130/0091-7613(1986)14<242:AOFZLA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Allen Lowrie, Christian Smoot, Rodey Batiza; Are oceanic fracture zones locked and strong or weak?: New evidence for volcanic activity and weakness. Geology 1986;; 14 (3): 242–245. doi: https://doi.org/10.1130/0091-7613(1986)14<242:AOFZLA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Traditionally, oceanic fracture zones and other lithospheric and crustal faults have been viewed as zones of weakness that are vulnerable to seismic and volcanic activity. This notion has recently been questioned on the basis of evidence showing that initial depth offsets (scarp height) across some Pacific fracture zones are preserved even after ∼100 m.y. of differential subsidence. This evidence suggests that some parts of oceanic fracture zones are locked shortly) after they drift away from ridge-transform intersections. Because the fracture zones seem to be strong welds, differential cooling stresses cause flexure in the lithosphere on both sides of the fracture. In this paper we briefly review the seemingly contradictory evidence for the thermomechanical characteristics of oceanic fracture zones (locked and strong vs. slipped and weak) and present new evidence indicating that parts of some fracture zones are volcanically active. Volcanism is an indication of relative weakness because strain and failure are required to open volcanic conduits. This and other evidence for the inherent weakness of fracture zones can be reconciled with evidence for strength if different segments of fracture zones exhibit contrasting thermomechanical behavior. More data are needed to determine whether this is so and whether there are systematic patterns of distribution for weak and strong parts of individual fracture zones. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.