Metadata Report for BODC Series Reference Number 705429

• 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

Teledyne RDI's Workhorse Monitor ADCP

The Workhorse Monitor acoustic doppler current profler (Teledyne RD Instruments) is a long-range and long-term self contained ADCP. It has a patented four beam signal (300, 600 or 1200 kHz) and a standard depth rating of 200m or 600m. It operates effectively between temperatures of -5°C and 45°C and has a velocity accuracy of ±1% ±5mm/s.

James Clark Ross JCR97 Lowered Acoustic Doppler Current Profiler data

Originator's processing

Full instructions for LADCP deployment and recovery during JCR97, details of the configuration files and, more information on the issues encountered can be found in the Cruise report

The following is adapted from the cruise report section written by Kevin Oliver and Justin Buck.

The LADCP package used during JCR97 consisted of a downward and an upward looking RDI 300 kHz Workhorse (WH) ADCP. The downward-looking Workhorse (DWH; serial number 4908) was mounted off-centre at the bottom of the frame, and the upward-looking Workhorse (UWH; serial number 1855) was mounted on the outside of the frame. The details of their sampling configurations are described in the secion below. Between stations, each ADCP was usually connected to a controlling PC in the Underway Instrument Control (UIC) room through a serial cable for delivery of pre-deployment instructions and post-deployment data retrieval. When sea-ice necessitated lowering the package from the aft of the ship, this was impossible due to insufficient length of cable, and the ADCPs were allowed to continue pinging between stations. The battery package was recharged after each deployment, by connection to a charging unit in the UIC room via a power lead.

Both instruments were deployed during every station except for station 79. At every station except the test station (station 999), where no data were obtained as a result of a minor error in the command file for the master DWH, both ADCPs returned reasonable raw data. The data quality during downcasts/upcasts was poorer during stations 62-72 and 82 when alternative sampling configurations were used (see configuration section below). For other stations, inspection typically revealed better agreement with the shipboard ADCP for DWH downcasts than DWH upcasts.

Processing of data from each Workhorse was carried out independently using the same University of Hawaii (UH; Eric Firing's group) software that was used on JCR106 and JCR80, detailed in the processing section. Because problems were encountered, the data were also processed using software by Lamont Doherty Earth Observatory (LDEO; Martin Visbeck's group). Use of this software is not detailed here. Because tables of the earth's magnetic variation were not updated to 2005 in the UH software, the magnetic field information for the equivalent date in 2004 was used. The error associated with this is likely to be smaller than the precision of the ADCP compasses, and was not detectable from comparison with the LDEO software output for the DWH. There was good agreement between raw data from the DWH and the UWH. Raw outputs showed good agreement on spatial scales greater than the range of the ADCPs but negative correlation on smaller spatial scales. On this basis, it is suspected that the UH software was either treating the UWH as a DWH, or was misinterpreting the bin distances from the UWH. Modification of the LDEO software has provided processed UWH data that agree well with DWH data.

JCR97 LADCP configuration files

Three different sampling configurations were used for different stations, depending on the primary purpose for which the ADCPs were used. The majority of stations consisted of conventional single down-and-up casts with pauses for bottle firing. For such stations, as well as for 'yoyo' stations (stations 26-28), consisting of multiple repeats of conventional casts, the priority was obtaining the best possible current estimates despite package motion and a short observation period for each part of the water column. As is usual for this purpose, the ADCPs were operated with 16 large (10 m) bins and short ensembles (1 ping per ensemble; average 1 ping/second). At some stations, the package was held for up to 30 minutes at one or more depths (frequently with repetition), for observation of a dense plume from the Filchner continental shelf. In such cases, package motion and limited observation time were lesser concerns, and good quality ensembles with high spatial resolution were priorities. For stations 27 and 62- 71 four metre bins were used for each WH. This was also the case for stations 72 and 82, with the further alteration that 300 ping ensembles were used.

Plume stations LADCP data

The aim of stations 72 and 82 was to capture the plume of Ice Shelf Water (ISW) originating from the Filchner Ice Shelf Cavity and flowing into the deep Weddell Sea. The CTD package followed the cycle described in the table below. The navigation, temperature and, salinity were logged at each stage. The aim is to analyse the temporal variability of the plume. The reason for choosing to hold the package at 90 m and 180 m above the bottom is so the LADCPs can get a profile for the whole plume.

BODC Processing

The data were sent to BODC in Matlab binary .MAT files. The files contained data from the 'upcast', 'downcast' and, 'meancast' for each ADCP. It was decided that only data from the 'downcast' would be transferred as per BODC data banking guidelines. The data was transferred to QXF format using BODC generated Matlab code. Each variable within the original files is assigned a unique BODC parameter code. The parameter code mapping can be seen below.

The data were screened using BODC in-house visualisation software and any suspect data points were 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: