Metadata Report for BODC Series Reference Number 1012810

• 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

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 Simrad EA500 bathymetric echosounder

The EA500 is a bathymetric echosounder that can be used in water as deep as 10,000 m. It features triple frequency operation with a separate digitiser for each channel and high transmitted power with an instantaneous dynamic range of 160 dB. The instrument can operate with several pulses in the water simultaneously and has bottom tracking capabilities. A wide range of transducers (single beam, split beam or side-looking) is available and the ping rate is adjustable up to 10 pings per second. The split beam operation measures the athwartships inclination angle of the seabed.

This instrument was introduced in June 1989 and and replaced by the EA 600 in 2000.

Specifications

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

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.

Ashtech Global Positioning System receivers (ADU series)

The ADU series of Global Positioning System (GPS) receivers are designed to give real-time three-dimensional position and attitude measurements. Attitude determination is based on differential carrier phase measurements between four antennas connected to a receiver, providing heading, pitch and roll, along with three-dimensional position and velocity.

The ADU2 model receives information from 48 channels, while the upgraded model (ADU5) uses 56 channels. The ADU5 also features a unique Kalman filter with user selectable dynamic modes to match operating conditions. It also incorporates signals from Satellite Based Augmentation Systems (SBAS) and features an embedded 2-channel 300 kHz beacon receiver for easy differential GPS (DGPS) operations.

Specifications

Further details can be found in the manufacturer's specification sheets for the ADU2 andADU5.

Instrument Description (JR106 navigation and bathymetry)

Data were collected using the integrated underway system on the RRS James Clark Ross. Contacts for specific instrumentation queries can be found on the British Antarctic Survey (BAS) website (BAS website).

At the time of the cruise, the JCR used a combination of an Ashtech ADU5, an Ashtech Glonass GG24 and a Trimble 4000 system for navigation and determination of ship positional and motion data. The JCR was also equipped with a Seatex multibeam GPS that is used by the Kongsberg EM120 bathymetry system.

Sea-floor depth measurements were determined with a Simrad EA500 navigational echo-sounder and a Kongsberg EM120 multi-beam swath hydrographic echo-sounder. Both used hull-mounted tranducers.

Specific details of navigational and bathymetry instrumentation:

References

Cruise report - JR106b, RRS James Clark Ross, NERC AutoSub under ice thematic Programme, Kangerdlugssuaq Fjord and Shelf, East Greenland.

BODC JR106b documentation

Underway navigation processing document

Originator's processing

Navigation

On a daily basis an ASCII file, get_bestnav, containing the RVS 'bestnav' position data at 30-second intervals was produced containing the ship's latitude, longitude, distance traveled and direction. The resulting navigational output was converted into a .mat file, a standard Matlab output file with the application of a Matlab script that combines all daily output produced into a master file, bestnav_all_jr106.mat and checks to see if values were flagged as good.

Bathymetry

Sea-floor depth measurements from the Simrad EA500 hydrographic echosounder and a hull mounted transducer were converted into an ASCII file on a daily basis at 2-6 second intervals. The bathymetry data were then mapped to the same 30 second time interval as the navigational data. The merged_all_jr106s.mat file containing navigation and bathymetry data from the leg was output by this process.

BODC Processing

Data were received as three binary .mat Matlab files named bestnav_all_jr106.mat, merged_all_jr106s and oceanlog_30sec_all_jr106s.mat. Each file held data from the navigation, bathymetry and oceanographic/meteorological respectively although each file contained both position and time data. The data covered the time period of 18:24:29 on the 29th August 2004 to 23:59:29 on the 10th September 2004, and so include data from the previous cruise (JCR106). Data from the previous cruise were trimmed from this series as they are included in the JCR016 data submission.

All underway sea surface hydrography, meteorology and ship's navigation files were merged into a single NetCDF file using time (GMT) as the primary linking key.

Following this, the NetCDF file was then split into three separate NetCDF files, with the data grouped by instrument position, by BODC generated Matlab code. One file contained data for sea surface hydrography, one for meteorology and the final NetCDF file held navigation data.

Positions were checked for gaps and improbable speeds. Gaps were filled with interpolated data points flagged with the appropriate BODC data quality control flag.

The GEBCO bathymetry channel (MBANGBCE) was added to the dataset by BODC and an intercomparison of the bathymetry and the GEBCO bathymetry conducted.

During transfer the original variables were mapped to unique BODC derived parameter codes. The parameter mapping is described in the table below.

Each data channel was visually inspected on a graphics workstation and any spikes or periods of dubious data are flagged as suspect. The capabilities of the workstation screening software allows all possible comparative screening checks between channels (e.g. to ensure corrected wind data have not been influenced by changes in ship's heading). The system also has the facility of simultaneously displaying the data and the ship's position on a map to enable data screening to take oceanographic climatology into account.

Project Information

AutoSub Under Ice (AUI) Programme

AutoSub was an interdisciplinary Natural Environment Research Council (NERC) thematic programme conceived to investigate the marine environment of floating ice shelves with a view to advancing the understanding of their role in the climate system.

The AUI programme had the following aims:

• To attain the programme's scientific objectives through an integrated programme based on interdisciplinary collaborations and an international perspective
• To develop a data management system for the archiving and collation of data collected by the programme, and to facilitate the eventual exploitation of this record by the community
• To provide high-quality training to develop national expertise in the use of autonomous vehicles in the collection of data from remote environments and the integration of such tools in wider programmes of research
• To stimulate and facilitate the parameterising of sub-ice shelf processes in climate models, and to further demonstrate the value of autonomous vehicles as platforms for data collection among the wider oceanographic and polar community

Following the invitation of outline bids and peer review of fully developed proposals, eight research threads were funded as part of AUI:

Physical Oceanography

• ISOTOPE: Ice Shelf Oceanography: Transports, Oxygen-18 and Physical Exchanges.
• Evolution and impact of Circumpolar Deep Water on the Antarctic continental shelf.
• Oceanographic conditions and processes beneath Ronne Ice Shelf (OPRIS).

Glaciology and Sea Ice

• Autosub investigation of ice sheet boundary conditions beneath Pine Island Glacier.
• Observations and modelling of coastal polynya and sea ice processes in the Arctic and Antarctic.
• Sea ice thickness distribution in the Bellingshausen Sea.

Geology and Geophysics

• Marine geological processes and sediments beneath floating ice shelves in Greenland and Antarctica: investigations using the Autosub AUV.

Biology

• Controls on marine benthic biodiversity and standing stock in ice-covered environments.

The National Oceanography Centre Southampton (NOCS) hosted the AUI programme with ten further institutions collaborating in the project. The project ran from April 2000 until the end of March 2005, with some extensions to projects beyond this date because of research cruise delays. The following cruises were the fieldwork component of the AUI project:

Table 1: Details of the RRS James Clark Ross AUI cruises.

All the cruises utilised the AutoSub autonomous, unmanned and untethered underwater vehicle to collect observations beneath sea-ice and floating ice shelves. AutoSub can be fitted with a range of oceanographic sensors such as:

• Conductivity Temperature Depth (CTD) instruments
• Acoustic Doppler Current Profillers (ADCP)
• A water sampler
• Swath bathymetry systems
• Cameras

In addition to use of AutoSub during each cruise measurements were taken from ship. These varied by cruise but included:

• Ship underway measurements and sampling for parameters such as:
  • Salinity
  • Temperature
  • Fluorescence
  • Oxygen 18 isotope enrichment in water
  • Bathymetry using a swath bathymetry system
• Full-depth CTD casts for with observations of samples taken for parameters such as:
  • Salinity
  • Temperature
  • Fluorescence
  • Optical transmissivity
  • Dissolved oxygen
  • Oxygen 18 isotope enrichment in water
  • Water CFC content
• Sea floor photography and video using the WASP system
• Sea floor sampling with trawls/rock dredges
• Sea ice observations (ASPeCt), drifters and sampling

The AutoSub project also included numerical modelling work undertaken at University College London, UK.

The project included several firsts including the first along-track observations beneath an ice shelf using an autonomous underwater vehicle. The AutoSub vehicle was developed and enhanced throughout this programme and has now become part of the NERC equipment pool for general use by the scientific community. Further information for each cruise can be found in the respective cruise reports (links in Table 1).

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: