Metadata Report for BODC Series Reference Number 1902106

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

JR20120120 (JR255A) Underway: Navigation Data Quality Document

Cycle 18323 of the data series was deleted due to a duplicate time. All corresponding data for this cycle was also deleted as the values were consistent with the previous instance of this time stamp.

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Kongsberg EA600 Single Beam Echosounder

The EA600 is a single beam echosounder with full ocean depth capability designed for bathymetric surveys. It measures water depth by monitoring the travel time of an acoustic signal that is transmitted from the ship, reflected off the seabed and received back at the ship.

The main components of the system are hull-mounted transducers linked to general purpose transceivers (GPTs). Up to four GPTs, each controlling one or more transducers, may be operated simultaneously. The GPT generates a signal, which is transmitted into the water column as an acoustic pulse by the transducer array, and the returning echo is recorded by the GPT. GPTs are in turn linked to a combined display and processor, where adjustments (such as sound-speed corrections) may be applied to the data. Available frequencies span from 12 to 710 kHz, and each GPT may operate at a separate frequency. A variety of transducers is available for water depths up to 11,000 m.

The EA600 stores all data internally but has a USB port which allows the possibility of connecting a CD-ROM/DVD drive to read and write the data. All echo data can be stored as files: bitmap, sample, depth or sidescan data.

In deeper waters, the EA600 supports a multipulse function, allowing for a higher pinger rate. While on passive mode, the pinger is normally attached to a device, with the purpose of tracking and displaying its current depth.

The EA600 replaced the EA500 in 2000.

Specifications

Further details can be found in the manufacturer's specification sheet.

Kongsberg EM122 12kHz Multibeam Echosounder

The EM122 is designed to perform seabed mapping to full ocean depth with a high resolution, coverage and accuracy. Beam focusing is applied both during reception and transmission. The system has up to 288 beams/432 soundings per swath with pointing angles, which are automatically adjusted according to achievable coverage or operator defined limits.

This model uses both Continuous Wave and Frequency Modulated sweep pulses with pulse compression on reception, in order to increase the maximum useful swath width. The transmit fan is split in several individual sectors, with independent active steering, in order to compensate for the vessel movements.

In multiplying mode, two swaths per ping cycle are generated, with up to 864 soundings. The beam spacing is equidistant or equiangular and the transmit fan is duplicated and transmitted with a small difference in along track tilt, which takes into account depth coverage and vessel speed, to give a constant sounding separation along track. In high density mode, more than one sounding per beam can be produced, such that horizontal resolution is increased and is almost constant over the whole swath.

The EM122 transducers are modular linear arrays in a Mills cross configuration with separate units for transmit and receive. If used to deliver sub-bottom profiling capabilities with a very narrow beamwidth, this system is known as SBP120 Sub-Bottom Profiler.

The specification sheet can be accessed here Kongsberg EM122.

Specifications

EM122 versions

Ashtech GG24 receiver

The GG24 is an all-in-view Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) receiver that blends GPS and GLONASS into a single position solution. This receiver uses all available satellites from both systems to obtain the best position information.

The three-dimensional position and velocity are calculated when tracking any combination of five satellites. Up to five independent measurements are determined every second, with no interpolation or extrapolation from previous solutions.

Specifications

Further details can be found in the manufacturer's specification sheet.

Chernikeeff Aquaprobe Mk5 Electromagnetic Speed Log

The Aquaprobe Mk5 EM Speed Log operates on the principle that a conductor (such as water) passing through an electromagnetic field will create a voltage whose magnitude increases as the speed of the conductor increases. The EM log includes one or two hull-mounted transducers, which generate an electromagnetic field and measure the voltage created by the flow of water through that field, thereby deducing the speed of the vessel through the water.

The EM log has the options of single or twin transducers, single or dual axis speed measurements and gate-valved (retractable) hull fitting or fixed transducers. The microprocessor calibration control ensures a high accuracy through the entire speed range.

Specifications

Further details can be found in the manufacturer's specification sheet.

Furuno GPS/WAAS Navigator GP32

The GP32 is an advanced GPS navigator with a Wide Area Augmentation System (WAAS) receiver which can receive up to 12 discrete GPS channels, all-in-view, and also has DGPS capabilities.

The WAAS applies correction data by means of geostationary satellites. The reference stations on earth monitor the GPS constellation and route GPS error data to the WAAS satellite via the master earth station.

This equipment is comprised of a compact unit designed for coastal activities with several display modes, e.g. Plotter, Nav Data, Steering, Highway, Speedometer and two other costumisable modes. The data can be viewed in WGS-84 or other geodetic systems.

Specifications

The equipment's specification sheet can be accessed Furuno GP32

Kongsberg Seatex Seapath 320+ Precise Heading, Attitude and Positioning Sensor

The Seapath 320+ is a navigational system that combines two Global Navigation Satellite System (GNSS) receivers with a MRU 5+ inertial sensor to provide high resolution and accuracy positional data. The inertial sensor employs linear accelerometers and unique microelectromechanical systems (MEMS)-type angular rate gyros to provide 0.01 RMS pitch and roll accuracy. The GNSS receivers can use multiple satellite constellations (GPS, GLONASS and Galileo, when available), and combine data from these to improve heading and positional measurements. In case of missing data from one GNSS receiver, the other receiver provides position and velocity, and the inertial sensor provides heading from its internal rate sensors.

The main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 320+ .

Specifications

Sperry Marine MK-37 Gyrocompass

A family of instruments that contain a controlled gyroscope which seeks and aligns itself with the meridian and points to true north. They use the properties of the gyroscope in combination with the rotation of the earth and the effect of gravity. The effects of varying speed and latitude are compensated for by the use of manually operated controls. Models MOD I, MOD O, MOD D, MOD D/E are all with an analog output Step or/and Syncro. MOD VT is the latest model with NMEA Data output as well.

Further specifications for MOD VT can be found in the manufacturer's specification document.

Further information for MOD D/E can be found in the user manual.

JR20120120 (JR255A) Underway: Navigation Instrument Description

The navigation instruments used to collect this data set are presented in the table below.

JR20120120 (JR255A) Underway: Navigation Processing Procedures Document

Sampling Strategy

RRS James Clark Ross cruise JR255A was deployed as part of the Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project. JR255A was a 2 week cruise departing from port Stanley in the Falkland Islands. The GENTOO fieldwork took place in the Weddell Sea where gliders were used primarily for data gathering.

Data Processing

A script on the JRLC server (written by Bastien Queste) was run automatically every hour at quarter past to update the file the oceanlogger matlab file.

The routine first creates a query file which contains a GMT start and end time. The start time is either the first date recorded by the oceanlogger (18:36 17/01/2012) or the last date stored in the oceanlogger matlab file (if present) and the current time as an end time.

A perl script is then run by BAS IT Jeremy Robst to obtain the variables from the oceanlogger, the ship's navigation and the anemometer defined in the xml file; with data1 and data2 both being measured on the mast (data2 is measured in case data1 is wrong).

Navigation instruments were located on the ship's monkey island, above the bridge and the EM122 and EA600 on the ship's hull.

Navigation data were logged every second to the SCS system and stored in comma separated format in .ACO files and the header information in .TPL files. Each instrument logged data to one individual file.

Navigation data originated from the Furuno GPS, ship's orientation from the Sperry Marine gyrocompass and ship's speed and direction over ground from the GLONASS, the Furuno and Seatex GPS, speed through water from the Chernikeeff Aquaprobe and ship's heading from the Ashtech GPS.

Before the results were mapped, the outliers are removed from the data. The Originator chooses a threshold T (e.g. 20), for each parameter and then calculates x1 —value of the parameter corresponding to the Tth percentile- and x2 —for the 100-T th percentile.

After testing the scaling factor (SF) is set to 7, then the Originator sets to NaN any outliers with the following equations:

x < x1 — SF*(x2 — x1)

x > x2 + SF*(x2 — x1)

Files delivered to BODC

BODC Data Processing

The files mentioned above were selected for data banking as they contain the best version of processed position, heading and bathymetry. Data were banked at BODC following standard data banking procedures, including reduction through averaging, checking navigation channels for improbable values, working out speed over ground, and screening the data for anomalous values.

The originator's variables were mapped to appropriate BODC parameter codes as follows:

Project Information

Gliders: Excellent New Tools for Observing the Ocean (GENTOO)

Funding

Funding was provided by NERC through the 11^th round of the Antarctic Funding Initiative (AFI), an annual competition-based award which is supported logistically by the British Antarctic Survey (BAS). The award had a total value of £1,070,531 which was split between different researchers at various international institutions in the form of grants, fellowships and training grant records.

Project dates - 06 September 2010 to 31 March 2015

Background

Research has shown that surface waters surrounding Antarctica play an important role in driving the global oceanic circulation as they are subjected to ideal physical conditions to become denser and sink at specific locations. The mapping of these locations and the identification of the properties of these water cells have been relying on expensive and season-dependent shipborne observations in impractical polar seas. This study aims at revealing the potential of Seagliders, which are autonomous, inexpensive and sustainable underwater vehicles able to carry out certain physical, biological and chemical measurements of the water column all year round. Seagliders were deployed in the Weddell Sea, as the recent collapse of the Larsen Ice Shelf has raised questions on whether dense water may now be spilling off the continental shelf on the eastern side of the Antarctic Peninsula. Changes in location of deep water formation may affect local oceanic currents and consequently the global circulation and the Earth's climate; reliable mapping and description of the Antarctic waters are therefore key to generate accurate climate and circulation models and predictions. Possible changes in the ocean currents also affect the organisms living in the waters near Antarctica. In particular, krill lay eggs around the Antarctic Peninsula and rely on ocean currents to transport them to South Georgia. It is important to determine whether changes in the local circulation may impact krill's ecosystem, as animals such as whales, seals and penguins feed on them and they support a multi-million pound krill fishing industry. In light of the decreasing availability of resources for an increasing human population, the possibility of krill's immunity to temperature and circulation changes may result in a popular food resource for people in the future.

Objectives

The main objectives of the GENTOO project depend on a critical evaluation of the ability to measure current velocity and krill biomass from a glider.

1) To quantify and understand the possible new source of dense water overflow and its variability; to determine the outflow's potential as an early indicator of Antarctic climate change; to assess the impact of changing dense overflows on the locations and strengths of the surface currents and frontal jets; to provide valuable constraints for climate models that describe how changes in ocean circulation feedback on and regulate climate change in polar latitudes.

2) To determine the krill biomass distribution and (temporal and spatial) variability to the east of the Antarctic Peninsula and its likely impact on the circumpolar krill ecosystem; to assess the impact of any variations in the location of the frontal jets (from objective 1) on the krill biomass distribution; to alleviate a severe regional lack of field data on krill, a key species in the Antarctic food web.

Participants

• University of East Anglia, United Kingdom (Lead Research Organisation)
• NOAA - National Oceanic and Atmospheric Administration, United States
• Bjerknes Centre for Climate Research, Norway
• AWI - Alfred Wegener Institute for Polar and Marine Research, Germany
• VIMS - Virginia Institute of Marine Science, United States

• Prof. Karen Heywood, University of East Anglia, Environmental Science (Principal Investigator)
• Dr. Sophie Fielding, NERC British Antarctic Survey, Science Programmes
• Prof. Gwyn Griffiths, National Oceanography Centre, Science and Technology
• Dr. Stuart Dalziel, University of Cambridge, Applied Mathematics and Theoretical Physics
• Dr. Eugene Murphy, NERC British Antarctic Survey, Science Programmes
• Dr. Andrew Thompson, California Institute of Technology, Environmental Science and Engineering.

Methodology

During cruise RRS James Clark Ross 255A three Seagliders were deployed, and a hydrographic survey was undertaken together with nets and underway biological, chemical and physical measurements. The data gathered was analysed to meet the objectives listed above. Please read the 'Instrumentation' section below, and visit the GENTOO website for more information on the methodology and outcomes of the various research studies.

Fieldwork

• RRS James Clark Ross 255A - 20 January 2012 to 03 February 2012. Port of arrival and departure is Stanley, Falkland Islands (Malvinas). Study area - Drake Passage, Weddell Sea, Powell Basin. Principal Scientist - Dr. Karen Heywood, University of East Anglia. This was the glider deployment cruise and the primary data gathering exercise.
• RRS James Clark Ross 255B - 07 February 2012 to 22 March 2012. Port of arrival and departure is Stanley, Falkland Islands (Malvinas). This was the glider recovery cruise; other projects not linked to GENTOO shared the voyage.

Instrumentation

• Seagliders - three in total, each equipped with a Seabird CT sail (i.e. free-flushed temperature and conductivity sensors), Aandera oxygen optode and a WETLabs ECO Triplet. (Biddle et al. 2015)
• SeaBird (SBE) CTD-11plus rosette equipped with 24 12-litre Niskin bottles. Sensors installed are SBE 43 Oxygen sensor, LI-COR Biospherical PAR Sensor, Chelsea Aqua 3 Fluorometer, WET Labs C-Star Transmissometer, and Altimeter sensor.
• 300 kHz WorkHorse (WH) Lowered Acoustic Doppler Current Profiler (LADCP)
• 75 kHz RD Instruments Ocean SUrveyor (OS75) Vessel-Mounted Acoustic Doppler Current Profiler (ADCP)
• Surface drifters: 20 Clearsat-15 Minidrogue drifters with a GPS navigation option and 20 Clearsat-15 SVP Minidrigue drifters with Argos data telemetry, both purchased from Clearwater Instrumentation, Inc.
• Three AOEX-SBE Argo floats profilers produced by Webb Research Corporation USA.
• RMT8 Nets Macrozooplankton
• Guildline Autosal salinometer
• Winkler O₂ titrator
• Simrad EK60 Echo Sounder
• Underway - navigation, surface and meteorology.

Contacts

References

Biddle, L.C., Kaiser J., Heywood K.J., Thompson A.F., and Jenkins A., 2015. Ocean glider observations of iceberg-enhanced biological production in the northwestern Weddell Sea, Geophys. Res. Lett. (42), 459-465.

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: