Kemp
John N.
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John N.
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Technical ReportDesign and operation of automated ice-tethered profilers for real-time seawater observations in the polar oceans(Woods Hole Oceanographic Institution, 2006-06) Krishfield, Richard A. ; Doherty, Kenneth W. ; Frye, Daniel E. ; Hammar, Terence R. ; Kemp, John N. ; Peters, Donald B. ; Proshutinsky, Andrey ; Toole, John M. ; von der Heydt, KeithAn automated, easily-deployed Ice-Tethered Profiler (ITP) has been developed for deployment on perennial sea ice in polar oceans to measure changes in upper ocean temperature and salinity in all seasons. The ITP system consists of three components: a surface instrument that sits atop an ice floe, a weighted, plastic-jacketed wire-rope tether of arbitrary length (up to 800 m) suspended from the surface instrument, and an instrumented underwater unit that profiles up and down the wire tether. The profiling underwater unit is similar in shape and dimension to an ARGO float except that the float's variable-buoyancy system is replaced with a traction drive unit. Deployment of ITPs may be conducted either from ice caps or icebreakers, utilizing a self contained tripod/winch system that requires no power. Careful selection of an appropriate multiyear ice floe is needed to prolong the lifetime of the system (up to 3 years depending on the profiling schedule). Shortly after deployment, each ITP begins profiling the water column at its programmed sampling interval. After each acquired temperature and salinity profile, the underwater unit (PROCON) transfers the data and engineering files using an inductive modem to the surface controller (SURFCON). SURFCON also accumulates battery voltages, buoy temperature, and locations from GPS at specified intervals in status files, and queues that information for transmission at the start of each new day. At frequent intervals, an Iridium satellite transceiver in the surface package calls and transmits queued status and CTD data files onto a WHOI logger computer, which are subsequently processed and displayed in near-real time at http://www.whoi.edu/itp. In 2004 and 2005, three ITP prototypes were deployed in the Arctic Ocean. Each system was programmed with accelerated sampling schedules of multiple one-way traverses per day between 10 and 750-760 m depth in order to quickly evaluate endurance and component fatigue. Two of the ITPs are continuing to function after more than 10 months and 1200 profiles. Larger motor currents are observed at times of fast ice floe motion when larger wire angles develop and drag forces on the profiler are increased. The CTD profile data so far obtained document interesting spatial variations in the major water masses of the Beaufort Gyre, show the double-diffusive thermohaline staircase that lies above the warm, salty Atlantic layer, and many mesoscale eddys. Deployed together with CRREL Ice Mass Balance (IMB) buoys, these ITP systems also operate as part of an Ice Based Observatory (IBO). Data returned from an array of IBOs within an Arctic Observing Network will provide valuable real time observations, support studies of ocean processes, and facilitate numerical model initialization and validation.
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Technical ReportCLIVAR Mode Water Dynamics Experiment (CLIMODE) fall 2005, R/V Oceanus voyage 419, November 9, 2005–November 27, 2005(Woods Hole Oceanographic Institution, 2006-02) Hutto, Lara ; Weller, Robert A. ; Fratantoni, David M. ; Lord, Jeffrey ; Kemp, John N. ; Lund, John M. ; Brambilla, Elena ; Bigorre, Sebastien P.CLIMODE (CLIVAR Mode Water Dynamic Experiment) is a program designed to understand and quantify the processes responsible for the formation and dissipation of North Atlantic subtropical mode water, also called Eighteen Degree Water (EDW). Among these processes, the amount of buoyancy loss at the ocean-atmosphere interface is still uncertain and needs to be accurately quantified. In November 2005, a cruise was made aboard R/V Oceanus in the region of the separated Gulf Stream, where intense oceanic heat loss to the atmosphere is believed to trigger the formation of EDW. During that cruise, one surface mooring with IMET meteorological instruments was anchored in the core of the Gulf Stream as well as two moored profilers on its southeastern edge. Surface drifters, APEX floats and bobby RAFOS floats were also deployed along with two other moorings with sound sources. CTD profiles and water samples were also carried out. This array of instruments will permit a characterization of EDW with high spatial and temporal resolutions, and accurate in-situ measurements of air-sea fluxes in the formation region. The present report documents this cruise, the instruments that were deployed and the array of measurements that was set in place.
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Technical ReportPreliminary acoustic and oceanographic observations from the ASIAEX 2001 South China Sea Experiment(Woods Hole Oceanographic Institution, 2001-09) Newhall, Arthur E. ; Costello, Lawrence ; Duda, Timothy F. ; Dunn, James M. ; Gawarkiewicz, Glen G. ; Irish, James D. ; Kemp, John N. ; McPhee, Neil M. ; Liberatore, Stephen P. ; Lynch, James F. ; Ostrom, William M. ; Schroeder, Ted ; Trask, Richard P. ; von der Heydt, KeithThe Asian Seas International Experiment (ASIAEX) was a very successful scientific collaboration between the United States of America (USA), the People’s Republic of China (PRC), Taiwan (ROC), the Republic of Korea (ROK), Japan, Russia, and Singapore. Preliminary field experiments associated with ASIAEX began in spring of 2000. The main experiments were performed in April-August, 2001. The scientific plan called for two major acoustics experiments, the first a bottom interaction experiment in the East China Sea (ECS) and the second a volume interaction experiment in the South China Sea (SCS). In addition to the acoustics efforts, there were also extremely strong physical oceanography and geology and geophysics components to the experiments. This report will concentrate on describing the moored component of the South China Sea portion of ASIAEX 2001 performed from the Taiwan Fisheries research vessel FR1 (Fisheries Researcher 1). Information on the environmental moorings deployed from the Taiwanese oceanographic research vessel OR1 (Oceanographic Researcher 1) will also be listed here for completeness, so that the reader can pursue later analyses of the data. This report does not pursue any data analyses per se.
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ArticleThe 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.
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Technical ReportOcean Bottom Seismometer Augmentation of the Philippine Sea Experiment (OBSAPS) cruise report(Woods Hole Oceanographic Institution, 2011-09) Stephen, Ralph A. ; Kemp, John N. ; McPeak, Sean P. ; Bolmer, S. Thompson ; Carey, Scott ; Aaron, Ernie ; Campbell, Richard L. ; Moskovitz, Brianne ; Calderwood, John ; Cohen, Ben ; Worcester, Peter F. ; Dzieciuch, Matthew A.The Ocean Bottom Seismometer Augmentation to the Philippine Sea Experiment (OBSAPS, April-May, 2011, R/V Revelle) addresses the coherence and depth dependence of deep-water ambient noise and signals. During the 2004 NPAL Experiment in the North Pacific Ocean, in addition to predicted ocean acoustic arrivals and deep shadow zone arrivals, we observed "deep seafloor arrivals" that were dominant on the seafloor Ocean Bottom Seismometer (OBS) (at about 5000m depth) but were absent or very weak on the Distributed Vertical Line Array (DVLA) (above 4250m depth). These "deep seafloor arrivals" (DSFA) are a new class of arrivals in ocean acoustics possibly associated with seafloor interface waves. The OBSAPS cruise had three major research goals: a) identification and analysis of DSFAs occurring at short (1/2CZ) ranges in the 50 to 400Hz band, b) analysis of deep sea ambient noise in the band 0.03 to 80Hz, and c) analysis of the frequency dependence of BR and SRBR paths as a function of frequency. On OBSAPS we deployed a fifteen element VLA from 12 to 852m above the seafloor, four short-period OBSs and two long-period OBSs and carried out an 11.5day transmission program using a J15-3 acoustic source.
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Technical ReportDeployment operation procedures for the WHOI Ice-Tethered Profiler(Woods Hole Oceanographic Institution, 2007-07) Newhall, Kris ; Krishfield, Richard A. ; Peters, Donald B. ; Kemp, John N.Deployed and fixed to a suitable multi-year ice floe, the Ice-Tethered Profiler (ITP) can sustain near-real time measurements of upper ocean temperature and salinity for up to three years. Incorporating a specifically designed winch system and deployment apparatus that is both light weight and easily assembled or disassembled on a ship or at a deployment site, the ITP can be deployed in less than four hours by either transporting the gear and field personnel to the deployment site via aircraft, or by lowering the gear over the side of a ship and hauling on the ice. Using daily satellite imagery (if available), visual reconnaissance flights, and ice surveying, the choice of an appropriate ice floe is a necessity to select a site that will sustain the system for a prolonged period of time (depending upon the instrument sampling rate). If available, the helicopter is the preferable method for surveying different sites and for deployment operations. Working from a ship typically limits the distance and selection of ice floes. Pre-deployment procedures include powering and configuring the ITP instruments and preparing the apparatus for transport to the deployment site. Specific deployment methods include the assembly and disassembly of the ITP winch, proper placement of the total ITP deployment apparatus, ‘Yale Grip’ braiding and slipping techniques, and testing the Iridium and Inductive communication links. The operations described here provide a safe and efficient manner to easily deploy the WHOI ITP.
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Technical ReportThe Beaufort Gyre Observing System 2004 : mooring recovery and deployment operations in pack ice(Woods Hole Oceanographic Institution, 2005-05) Kemp, John N. ; Newhall, Kris ; Ostrom, William M. ; Krishfield, Richard A. ; Proshutinsky, AndreySituated beneath the Arctic perennial ice pack, the principal components of the Beaufort Gyre Observing System are three deep-ocean bottom-tethered moorings with CTD and velocity profilers, upward looking sonars for ice draft measurements, and bottom pressure recorders. A major goal of this project is to investigate basin-scale mechanisms regulating freshwater and heat content in the Arctic Ocean and particularly in the Beaufort Gyre throughout several complete annual cycles. The methods of recovering and re-deploying the 3800 m long instrumented moorings from the Canadian Coast Guard Icebreaker Louis S. St. Laurent in August 2004 are described. In ice-covered regions, deployments must be conducted anchor-first, so heavier wire rope and hardware must be incorporated into the mooring design. Backup buoyancy at the bottom of the mooring is advised for backup recovery should intermediate lengths of the mooring system get tangled under ice floes during recovery. An accurate acoustic survey to determine the exact location of the mooring, adequate ice conditions, and skilled ship maneuvering are all essential requirements for a successful mooring recovery. Windlass (or capstan) procedures could be used for the recovery, but a traction winch arrangement is recommended.
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Technical ReportArray data acquisition with wireless LAN telemetry as applied to shallow water tomography in the Barents Sea(Woods Hole Oceanographic Institution, 1992-12) von der Heydt, Keith ; Kemp, John N. ; Lynch, James F. ; Miller, J. ; Chiu, Ching-SangThis report describes the application of a new technique of digital radio telemetry, based on a recently available wireless Local Area Network Ethernet adapter, to the need for realtime transmission of data from a vertical line array (VLA) of hydrophones to a nearby ship. The report is technical in nature and discusses the design and performance of the system as used during the Barents Sea Polar Front Experiment in August 1992. A key feature of the use of LAN technology in a "telemetry" application is the availability of Transmission Control Protocol (TCP) software for Ethernet hardware that greatly eases the task of achieving error free digital data over a radio link prone to dropouts.
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Technical ReportAcoustic and oceanographic observations and configuration information for the WHOI moorings from the SW06 experiment(Woods Hole Oceanographic Institution, 2007-05) Newhall, Arthur E. ; Duda, Timothy F. ; von der Heydt, Keith ; Irish, James D. ; Kemp, John N. ; Lerner, Steven A. ; Liberatore, Stephen P. ; Lin, Ying-Tsong ; Lynch, James F. ; Maffei, Andrew R. ; Morozov, Andrey K. ; Shmelev, Alexey A. ; Sellers, Cynthia J. ; Witzell, Warren E.This document describes data, sensors, and other useful information pertaining to the moorings that were deployed from the R/V Knorr from July 24th to August 4th, 2006 in support of the SW06 experiment. The SW06 experiment was a large, multi-disciplinary effort performed 100 miles east of the New Jersey coast. A total of 62 acoustic and oceanographic moorings were deployed and recovered. The moorings were deployed in a “T” geometry to create an along-shelf path along the 80 meter isobath and an across-shelf path starting at 600 meters depth and going shoreward to a depth of 60 meters. A cluster of moorings was placed at the intersection of the two paths to create a dense sensor-populated area to measure a 3-dimensional physical oceanography. Environmental moorings were deployed along both along-shelf and across-shelf paths to measure the physical oceanography along those paths. Moorings with acoustic sources were placed at the outer ends of the “T” to propagate various signals along these paths. Five single hydrophone receivers were positioned on the across shelf path and a vertical and horizontal hydrophone array was positioned at the intersection of the “T” to get receptions from all the acoustics assets that were used during SW06.
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ArticleShallow Water ’06 : a joint acoustic propagation/nonlinear internal wave physics experiment(Oceanography Society, 2007-12) Tang, Dajun ; Moum, James N. ; Lynch, James F. ; Abbot, Philip A. ; Chapman, Ross ; Dahl, Peter H. ; Duda, Timothy F. ; Gawarkiewicz, Glen G. ; Glenn, Scott M. ; Goff, John A. ; Graber, Hans C. ; Kemp, John N. ; Maffei, Andrew R. ; Nash, Jonathan D. ; Newhall, Arthur E.Since the end of the Cold War, the US Navy has had an increasing interest in continental shelves and slopes as operational areas. To work in such areas requires a good understanding of ocean acoustics, coastal physical oceanography, and, in the modern era, autonomous underwater vehicle (AUV) operations.
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Technical ReportAtlantic Long-Term Oceanographic Mooring (ALTOMOOR)(Woods Hole Oceanographic Institution, 1996-03) Frye, Daniel E. ; Merriam, Steve ; Eastwood, Robert L. ; Kemp, John N. ; McPhee, Neil M. ; Liberatore, Stephen P. ; Hobart, Edward ; Bocconcelli, Alessandro ; Tarbell, Susan A.The Atlantic Long-Term Oceanogrphic Mooring (ALTOMOOR) has been maintained offshore Bermuda since 1993 as a testbed for the evaluation of new data telemetry technologies and new oceanographic instrumentation. It is currently a joint project between the Woods Hole Oceanographic Institution and the University of Southern California This report documents the WHOI contributions which have focused on the development of new data telemetry methods and new mooring technology. Details of the instrumentation evaluations will be published separately. A new inductively-coupled telemetry technology for ocean moorings has been developed and tested on ALTOMOOR. The inductive link uses standard, plastic-jacketed mooring wire as the transmission path for data generated at the individual instruments installed on the mooring. The signals are inductively linked to the mooring wire via toroids clamped around the wire, thus avoiding the need for multiconductor electromechanical cables terminated at each instrument. Seawater provides the electrical return path. The inductive modems send and receive data at 1200b/s. A controller in the surface buoy collects data from each of the subsurface instruments and forwards the data to shore by traditional satellite telemetry (Argos) and by short range radio using a nearby ship as a store and forward node. The buoy-to-ship link operates over about 2 km at 10kBytes/sec. When the ship docks, data are offloaded automatically to a computer on shore which can be accessed via the Internet.
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Technical ReportBeaufort Gyre Freshwater Experiment : deployment operations and technology 2003(Woods Hole Oceanographic Institution, 2004-01) Ostrom, William M. ; Kemp, John N. ; Krishfield, Richard A. ; Proshutinsky, AndreyThe Beaufort Gyre Freshwater Experiment (BGFE) observational program was designed to measure the freshwater content of the upper ocean and sea ice in the Beaufort Gyre of the Arctic Ocean using bottom-tethered moorings, drifting buoys, and hydrographic stations. The mooring program required the development of a safe and efficient deployment method by which the subsurface system could be deployed in waters surrounded by sea ice. This report documents the mooring procedure used to deploy the three BGFE moorings from the CCGS Louis S. St- Laurent, during the Joint Western Arctic Climate Study – 2003 (August 6 – September 7). The technical details of the instrumentation attached to each mooring and the specific deployment parameters are described. Specifics pertaining to the deployment of four surface-tethered drifters in the ice are also documented.
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Technical ReportAt Sea Test 2 recovery cruise : Cruise 206 on board R/V Knorr April 10 - 15, 2012 Woods Hole - Woods Hole, MA(Woods Hole Oceanographic Institution, 2012-06) Weller, Robert A. ; Lund, John M. ; O’Brien, Jeff ; Kemp, John N. ; Kostel, Ken ; Waldorf, Walt ; Holm, Chris ; Risien, Craig ; Matthewson, Michael ; Trowbridge, John H.The R/V Knorr, on Cruise 206, carried out the recovery of three moorings for the Coastal and Global Scale Nodes (CGSN) Implementing Organization of the NSF Ocean Observatories Initiative. These three moorings are prototypes of the moorings to be used by CGSN at the Pioneer, Endurance, and Global Arrays. Knorr departed from Woods Hole, Massachusetts on April 10, 2012 and steamed south to the location of the mooring deployments on the shelf break. Over five days, April 10-15, Knorr surveyed the bottom at the planned mooring sites, recovered the moorings, and carried out preliminary investigations of mechanical and electrical functionality on the recovered moorings and mooring hardware, including observations of biofouling and corrosion. Knorr returned to Woods Hole on April 15, 2012.
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ArticlePersistent near real-time passive acoustic monitoring for baleen whales from a moored buoy: System description and evaluation(Wiley, 2019-06-24) Baumgartner, Mark F. ; Bonnell, Julianne M. ; Van Parijs, Sofie M. ; Corkeron, Peter ; Hotchkin, Cara ; Ball, Keenan R. ; Pelletier, Léo‐Paul ; Partan, James W. ; Peters, Donald B. ; Kemp, John N. ; Pietro, Jeff ; Newhall, Kris ; Stokes, Andrew ; Cole, Timothy V. N. ; Quintana, Ester ; Kraus, Scott D.1. Managing interactions between human activities and marine mammals often relies on an understanding of the real‐time distribution or occurrence of animals. Visual surveys typically cannot provide persistent monitoring because of expense and weather limitations, and while passive acoustic recorders can monitor continuously, the data they collect are often not accessible until the recorder is recovered. 2. We have developed a moored passive acoustic monitoring system that provides near real‐time occurrence estimates for humpback, sei, fin and North Atlantic right whales from a single site for a year, and makes those occurrence estimates available via a publicly accessible website, email and text messages, a smartphone/tablet app and the U.S. Coast Guard's maritime domain awareness software. We evaluated this system using a buoy deployed off the coast of Massachusetts during 2015–2016 and redeployed again during 2016–2017. Near real‐time estimates of whale occurrence were compared to simultaneously collected archived audio as well as whale sightings collected near the buoy by aerial surveys. 3. False detection rates for right, humpback and sei whales were 0% and nearly 0% for fin whales, whereas missed detection rates at daily time scales were modest (12%–42%). Missed detections were significantly associated with low calling rates for all species. We observed strong associations between right whale visual sightings and near real‐time acoustic detections over a monitoring range 30–40 km and temporal scales of 24–48 hr, suggesting that silent animals were not especially problematic for estimating occurrence of right whales in the study area. There was no association between acoustic detections and visual sightings of humpback whales. 4. The moored buoy has been used to reduce the risk of ship strikes for right whales in a U.S. Coast Guard gunnery range, and can be applied to other mitigation applications.
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Technical ReportKing Abdullah University of Science and Technology (KAUST) mooring deployment cruise and fieldwork report, fall 2008 R/V Oceanus voyage 449-5, October 9, 2008–October 14, 2008(Woods Hole Oceanographic Institution, 2009-07) Farrar, J. Thomas ; Lentz, Steven J. ; Churchill, James H. ; Bouchard, Paul R. ; Smith, Jason C. ; Kemp, John N. ; Lord, Jeffrey ; Allsup, Geoffrey P. ; Hosom, David S.King Abdullah University of Science and Technology (KAUST) is being built near Thuwal, Saudi Arabia with the goal of becoming a world-class, graduate-level research university. As a step toward this goal, KAUST has partnered with the Woods Hole Oceanographic Institution (WHOI) to undertake various studies of the oceanography of the Red Sea in order to establish a research program in ocean sciences by the time the university opens its doors in the fall of 2009. Two of the KAUST-WHOI research projects involve deployment of surface moorings and associated instrumentation to measure physical properties of the Red Sea, such as temperature, salinity, and currents, at four locations off the coast of Saudi Arabia. The goal of these measurements is to better understand the evolution and dynamics of the circulation and air-sea interaction in the Red Sea. Two surface moorings and two bottom tripods (PI, Steven Lentz) were deployed at 50-55-m depth near 21°57'N, 38°46'E over the continental shelf close to the Saudi coast. An additional surface mooring/bottom tripod pair was deployed near 21°58'N, 38°50'E at the outer fringe of a reef system directly onshore of the shelf mooring/tripod pairs (PI, Lentz). The coastal moorings carry instruments to estimate temperature, salinity, and fluorescence; and the nearby bottom tripods support instruments to measure bottom pressure and the vertical profile of the currents. Additional instruments, principally bottom temperature sensors, were deployed over the reef system onshore of the shelf moorings. One air-sea interaction mooring (PI, J. Thomas Farrar) was deployed at 693-m depth near 22°10'N, 38°30'E. The air-sea interaction mooring carries instruments for measuring temperature, salinity, (water) velocity, winds, air temperature, humidity, barometric pressure, incident sunlight, infrared radiation, precipitation, and surface waves. A coastal meteorological tower was also installed on the KAUST campus in Thuwal (PI, Farrar). These measurements are of value because there are few time series of oceanographic and meteorological properties of the Red Sea that can be used to characterize the circulation, test numerical models of the Red Sea circulation, or formulate theoretical models of the physics of the Red Sea circulation. These measurements will permit a characterization of the Red Sea circulation with high temporal resolution at the mooring locations, and accurate in-situ estimates of the air-sea exchange of heat, freshwater, and momentum. In October 2008, a cruise was made aboard the R/V Oceanus to deploy the shelf and air-sea interaction moorings, and other fieldwork (e.g., tower instrumentation and deployment of reef instrumentation) was conducted after the cruise. Some additional data were collected during the cruise with shipboard instrumentation. This report documents the cruise and the data collected during the fall 2008 fieldwork.
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PresentationLOCOMOOR : a LOw-COst MOORing for the measurement of internal solitary waves( 2000-05-09) Lord, Jeffrey ; Irish, James D. ; Duda, Timothy F. ; Kemp, John N.In order to supplement the ASIAEX field effort to measure the temporal and spatial structure of the internal solitary wave field in relationship to acoustic propagation and scattering studies, an array of low-cost temperature moorings (LOCOMOOR) has been developed. The basic concept is to provide spatial coverage as opposed to dense vertical resolution in temperature. Three temperature sensors on each mooring will adequately measure the time of passage of the internal solitary waves. A horizontal array of 20 of these moorings deployed for about three weeks will allow the internal solitary wave front geometry (curvature) and velocity to be measured as they propagate through the experiment region. The arrival time of each pulse within the packet of internal waves will be easily resolved, but the wave amplitude less exactly estimated. However, the amplitude will be very well measured by the velocity and density observations on the more heavily instrumented environmental moorings associated with the acoustic experiment.
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ArticleAcoustic travel-time variability observed on a 150-km radius tomographic array in the Canada Basin during 2016–2017(Acoustical Society of America, 2023-05-02) Worcester, Peter F. ; Dzieciuch, Matthew A. ; Vazquez, Heriberto J. ; Cornuelle, Bruce D. ; Colosi, John A. ; Krishfield, Richard A. ; Kemp, John N.The Arctic Ocean is undergoing dramatic changes in response to increasing atmospheric concentrations of greenhouse gases. The 2016–2017 Canada Basin Acoustic Propagation Experiment was conducted to assess the effects of the changes in the sea ice and ocean structure in the Beaufort Gyre on low-frequency underwater acoustic propagation and ambient sound. An ocean acoustic tomography array with a radius of 150 km that consisted of six acoustic transceivers and a long vertical receiving array measured the impulse responses of the ocean at a variety of ranges every four hours using broadband signals centered at about 250 Hz. The peak-to-peak low-frequency travel-time variability of the early, resolved ray arrivals that turn deep in the ocean was only a few tens of milliseconds, roughly an order of magnitude smaller than observed in previous tomographic experiments at similar ranges, reflecting the small spatial scale and relative sparseness of mesoscale eddies in the Canada Basin. The high-frequency travel-time fluctuations were approximately 2 ms root-mean-square, roughly comparable to the expected measurement uncertainty, reflecting the low internal-wave energy level. The travel-time spectra show increasing energy at lower frequencies and enhanced semidiurnal variability, presumably due to some combination of the semidiurnal tides and inertial variability.