Metadata Report for BODC Series Reference Number 1021991

• 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 quality report

The sdraft parameter is used to give an indication of the distance fro AutoSub to the bottom of any ice above the vehicle. However, during these deployments AutoSub was not deployed under any ice unless any happened to float over AutoSub at any point. This means that the majority of the data from this parameter is of no consequence.

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

Originator's Processing

AutoSub was deployed off the coast of Greenland in the Kangerdlugssuaq Fjord area. Floating ice and varying seawater densities in the survey area posed a problem for AutoSub. In order to enable AutoSub to dive below the surface wings were attached. Tests were then performed to ensure the wings worked as required before 5 full missions were performed. A summary of AutoSub deployments can be found below.

More information on the missions undertaken can be found on pages 11 - 14 in the cruise report, which is accessible through the metadata summary report.

ADCP data processing

AutoSub is fitted with two ADCP devices. An RDI 150 kHz downward looking ADCP and an RDI 300 kHz upward looking ADCP. Both ADCPs were set with 8 m profiling bins and data is recorded at 2 second intervals. AutoSub itself records data only every 2.6 seconds, so there are regular spaced data cycles that contain no data. The final processed ADCP data file was named m###ls2_proc3.mat where ### represents the mission number. The processed files also contained data binned to 100 m horizontally and with the upward and downward looking ADCP data combined together into one variable.

BODC Processing

The data were provided to BODC in 5 Matlab files. Data for both the upward and downward looking ADCPs were in the same file. Each file contained multiple versions of the data. One variable had the data binned to 100 m horizontally and one variable had combined the upward and downward looking ADCP data. It was decided that downward and upward ADCP ADCP data would be transferred separately and the combined variable would not be used. This was to make the final NETCDF files easier to understand and interpret. The raw 2 second bin data is transferred and not the horizontally binned data.

The data were transferred to NETCDF format using BODC generated Matlab code. Two NETCDF files were produced for each mission, one for the upward looking ADCP and one for the downward looking ADCP. The transfer involves mapping the originator's variables to unique BODC parameter codes. The parameter mapping can be seen below. Note that some codes are the same for two different variables. The variables are the same parameter and are from the different ADCPs so the codes can be the same as they are not in the same NETCDF file.

BODC Parameter Code Mapping

The data were then screened using BODC in-house visualisation software. Suspect data points are flagged with the appropriate data quality control flag.

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: