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  • 1
    Publication Date: 2017-10-17
    Description: Satellite records show a decline in ice extent over more than three decades, with a record minimum in September 2012. Results from the Pan-Arctic Ice-Ocean Modelling and Assimilation system (PIOMAS) suggest that the decline in extent has been accompanied by a decline in volume, but this has not been confirmed by data. Using new data from the European Space Agency CryoSat-2 (CS-2) mission, validated with in situ data, we generate estimates of ice volume for the winters of 2010/11 and 2011/12. We compare these data with current estimates from PIOMAS and earlier (2003–8) estimates from the National Aeronautics and Space Administration ICESat mission. Between the ICESat and CryoSat-2 periods, the autumn volume declined by 4291 km3 and the winter volume by 1479 km3. This exceeds the decline in ice volume in the central Arctic from the PIOMAS model of 2644 km3 in the autumn, but is less than the 2091 km3 in winter, between the two time periods.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Publication Date: 2022-05-25
    Description: Based upon the 1987-88 Arctic Environmental Drifting Buoy (AEDB), the Ice-Ocean Environmental Buoy (IOEB) was developed to acquire and telemeter in near real-time inter-relatable time-series data on atmospheric, oceanographic and ice physics in ice-covered oceans during all seasons. Two IOEBs were successfully deployed in two Arctic Sea Basin Stations in April, 1992. Since then, although some sensors malfunctioned, for 18 continuous months, they have been sending massive amounts of information. In this report we describe the technology which was developed for the 1991 IOEB. Mechanically, the IOEB consists of an extremely durable surface flotation package and an underwater mooring line of instruments and sensors. The apex contains data loggers for air, ice and engineering measurements, microcontroller modules for accumulating the data from all the instruments, and ARGOS platform transmit terminals (PTTs) for broadcasting the data. Extending above the surface float, a mast supports a wind monitor and air temperature probe, which along with a barometer provides meteorological data. Thermistor strings, vibrating wire stress sensors, and a thickness gauge are installed in the ice surrounding the buoy, and are interrogated by the modules inside the apex. In the ocean, 110m of conducting strength cable passes the data from conductivity/temperature recorders, an Acoustic Doppler Current Profier and data compression module, a dissolved oxygen sensor, a transmissometer and fluorometers to the PTT microcontrollers. Furthermore, a suspended particle collector and sediment trap transmit status information along the two-wire multidrop network cable. Because the IOEB differs from the AEDB by telemetering the majority of the scientific data, a complicated compression scheme is incorporated to broadcast the data from the 103 variables within the allowable 256-bit ARGOS data stream. Via Service ARGOS, this data currently becomes available to scientists in several countries within eight hours of transmission. In April 1992, two IOEBs were deployed at separate ice camps in the Arctic Ocean with battery power adequate to sustain the systems for over two years. One was deployed 115 miles from the North Pole in the center of the Transpolar Drift sea-ice current, and the other off of the coast of Alaska along the edge of the Beaufort Gyre. Airplanes capable of landing on ice were used for the transportation of the systems to their final destination. Simultaneously, a third, reduced version of the IOEB was deployed in the Weddell Sea by the Scott Polar Research Institute.
    Description: Funding was provided by the Office of Naval Research, Arlington, Virginia, USA and Japan Marine Science and Technology Center, Yokosuka, Japan.
    Keywords: Arctic ; Telemetry ; Underwater mooring
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 8010412 bytes
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  • 3
    Publication Date: 2022-05-25
    Description: There are strong reasons to gather data on polar oceanogrphy and climatology in real time using fully automated, unattended instrumentation systems for long periods; particularly during the inaccessible winter months when moving ice is extremely hazardous. We deployed an Artic Environmental Drifting Buoy (AEDB) on 4 August 1987 at 86°7'N, 22°3'E off of the FS Polarstern on a large 3.7 m thick ice island. The AEDB consisted of 2 major components: a 147 cm diameter surface float housing ARGOS transmitters and a data logger for ice-profiling thermistors, and a 125 m long mooring line attached to the sphere and fed though a 1m diameter ice hole. Along the mooring were deployed 2 fluorometers, conductivity and temperature loggers, an Acoustic Doppler Current Profiler (ADCP), a current meter, and a time-series sediment trap/micro-filter pump/transmissometer unit. The AEDB proceeded southwesterly with the Transpolar Drift at an average speed of 15.3 km/day, with a maximum speed of 88.8 km/day. On 2 January 1988, the AEDB dropped into the water while passing through the Fram Strait and for the remaining drift period was either free-floating on the water surface or underneath the sea ice. Throughout this period, the transmitters onboard successfully transmitted position, temperature, and strain caused by ice on the sphere. Although the sediment trap package was lost during the drift, valuable data was collected by the other instruments throughout the experiment. The ice thermistor data was used to determine oceanic heat flux, while continuous ADCP observations over the Yermak Plateau provided a wealth of information for understanding internal waves in the ice-covered ocean. The buoy was recovered by the Icelandic ship R/S Arni Fridriksson on 15 April 1988 at 65°17'N, 31°38'W, off southeatern Greenland, completing 3,900km of drift in 255 days. We are in the process of constructing the next automated stations which are planned for deployment in both the north and south polar regions in 1991-92.
    Description: Funding was provided by the Office of Naval Research, through grant Number NOOOI4-87,88,89,J-1288.
    Keywords: Transpolar drift ; Ice ocean environment ; ADCP ; Polarstem (Ship) Cruise ; Arni Fridriksson (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 5426126 bytes
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  • 4
    Publication Date: 2022-05-25
    Description: The 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.
    Description: Funding was provided by the National Science Foundation under Grant Number OPP-0230184.
    Keywords: Arctic operations ; Mooring deployments ; Beaufort Gyre Freshwater Experiment ; Louis S. St. Laurent (Ship) Cruise JWACS
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 28109513 bytes
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  • 5
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    Woods Hole Oceanographic Institution
    Publication Date: 2022-05-25
    Description: Filtered and Earth-referenced ADCP data from the B92, B97 and S97 IOEBs were demodulated to remove inertial and near-inertial tidal frequencies, in order to highlight the low frequency components for examination of Arctic submesoscale eddys. This report describes the raw data, processing scheme, and numerical and graphical results of this analysis, which are also available at http://ioeb.whoi.edu/ioebeddys.htm. Using the demodulated timeseries of current profiles from each buoy, characteristics of 95 possible eddy encounters are quantified by (1) identifying anomalously large velocities associated with subsurface vortices, (2) determining the vortex centers and their drift, and (3) determining vortex properties as a function of radius and depth. Out of 44 total months of observations, 81 of the encounters were determined to be subsurface eddies, and 29 were eddy core encounters. Only 14 of the confirmed subsurface encounters were cyclonic, versus 66 anticyclonic, and one indeterminate. Within the southern and central Canadian basin portion of the Beaufort Gyre, halocline eddys with maximum velocities between 10 and 45 cm/s, centered around 140 m depth, and over 100 m thick were prevalent. Over the Northwind Ridge, eddy encounters were absent from any timeseries. Farther north and west over the Chukchi Cap, encounters resumed, but were generally smaller, more shallow and less intense (although these observations were mostly derived from a lower resolution transmitted data subset).
    Description: Funding was provided by the National Science Foundation Grant No. OPP-9815303, and by the Office of Naval Research Grant No. N00014-97-1-0135.
    Keywords: Arctic halocline eddys ; Upper ocean currents ; Drifting buoy observations
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 15792824 bytes
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  • 6
    Publication Date: 2022-05-25
    Description: Situated 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.
    Description: Funding was provided by the National Science Foundation under Grant Number OPP-0230184 and Woods Hole Oceanographic Insitution’s Ocean and Climate Change Institute.
    Keywords: Arctic operations ; Mooring deployments ; Beaufort Gyre Observing System ; Louis S. St. Laurent (Ship) Cruise JWACS
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 2040937 bytes
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  • 7
    Publication Date: 2022-05-25
    Description: Between 1992 and 1998, three Ice-Ocean Environmental Buoys (IOEBs) were deployed a total of six times on multiyear pack ice in the Arctic Ocean. The processing scheme for the telemetered environmental data, as well as the individual IOEBs and field operations, are described, and the processed data are presented in graphical form. The IOEB Archived Data Processing (IADP) processing scheme was conceived specifically to remove noise in data telemetered from IOEBs caused by errors in network or satellite communications, and to calibrate to absolute values. The location data consists of Argos quality 2 or 3 positions from each platform transmit terminal (PTT) on a particular IOEB, which are subsequently screened, interpolated, and combined with similarly processed locations from the other PTT, and further smoothed with a 6-hr triangular filter to produce an hourly timeseries with a standard error estimated to be -150 m. The sensor data is prefiltered, combined, adjusted for buoy drift, and screened with a Gaussian first difference filter to produce unevenly spaced timeseries of each variable measured by the IOEB. Every variable is output to a unique file per year, per buoy consisting of a two-column ACSII timeseries. Drift and sensor data are presented from the 1992 Transpolar Drift IOEB which operated for only 4 months, IOEB-1 which drifted with the Beaufort Gyre in a large anticyclonic circle from April 1992 to November 1998, and IOEB-2 which drifted through the Fram Strait in 9 months in 1994, and 1997-98 was redeployed concurrently with SHEBA at a distance 50 km from the main camp.
    Description: Funding was provided by the Office of Naval Research under contract number N00014-99-10335 and Japan Marine Science and Technology Center.
    Keywords: Arctic buoy ; Air data ; Ice data ; Ocean data ; Environmental observations ; Ocean-atmosphere interaction ; Sverdrup II (Ship) Cruise ; Des Grosilliers (Ship) Cruise ; Louis S. St. Laurent (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 5216445 bytes
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  • 8
    Publication Date: 2022-05-26
    Description: An 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.
    Description: Funding was provided by the National Science Foundation under Contract Nos. OCE-0324233 and ARC-0519899.
    Keywords: Arctic instrumentation ; Ocean profiler ; Ice-based observatory ; Louis S. St. Laurent (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
    Format: 4139620 bytes
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  • 9
    Publication Date: 2022-05-26
    Description: 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.
    Description: Funding was provided by the National Science Foundation under Grant No. OCE-0324233 and by the Office of Polar Programs under award numbers ARC-0519899 and ARC-0631951.
    Keywords: Oceanographic buoys ; Oceanic mixing
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 10
    Publication Date: 2022-05-26
    Description: With the support of the National Science Foundation, we have completed the first cruise devoted to the GOFS and JGOFS program for the North Atlantic Bloom studies between March 28 and April 6 on board R/V Atlantis II. The major task of this cruise, to deploy bottom-tethered mooring arrays with time-series sediment traps along with current meters at two critical stations, 34°N and 47°N along 20°W, was accomplished. All 6 sediment traps, 3 on each array, were set at 14-day intervals for 13 periods from April 3 to September 26, 1989. Their opening and closing times were synchronized throughout the period of deployment. The arrays and instruments will be recovered and redeployed in September/October, 1989. Ancillary water column data, such as CTD, fluorometry, pigments, and major nutrient distribution, were also successfully completed (except for transmissometry profiling at the 47°N station) in order to understand the prebloom setting at JGOFS 34°N, 47°N, and 60°N stations. At the 47°N station on April 2, the mixed layer depth was 248m.
    Description: Funding was provided by the National Science Foundation through grant Number OCE 88-14228.
    Keywords: Joint Global Ocean Flux Study ; Marine sediments ; Atlantis II (Ship : 1963-) Cruise AII119-2
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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