Metadata Report for BODC Series Reference Number 1223140

• 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

JR239 75 kHz VMADCP: Data Quality Report

The data become more sparse the deeper the bin depth, with very few data cycles between bin number 47 and 58, after which there are no data. 70 bins were used, however, bins 66 to 70 did not contain any bin depths or data.

Note that there are changes in the bin depths and bin widths during the periods 20 March 2010 09:32:07 hours to 20 March 2010 12:50:47 hours, 22 March 2010 11:40:05 hours to 23 March 2010 09:33:35 hours and between 29 March 2010 03:46:07 hours and 29 March 2010 10:39:36 hours. These are related to changes in the LADCP settings which are detailed the Originator's Data Processing section and the cruise report.

Data Access Policy

Open Data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

JR239 75 kHz VMADCP: Instrument Description

A 75 kHz Teledyne RD Instruments Ocean Surveyor acoustic doppler current profiler (ADCP) fitted to the hull of the RSS James Clark Ross was used. The ship's hull depth is 6.47 m, the transducer depth is 6.3 m, the distance of the transducer behind the seachest window is 100-200 mm and the window thickness is 50 mm. The design draft of the ship is 6.3 m, which is subject to slight changes depending on load, with full load the draft is 6.4 m.

The navigation data was input from the Kongsberg Seatex Seapath 200 Global Positioning System receiver and Gyrocompass.

ADCP setup, data logging, preliminary screening and mapping of beam data onto Earth coordinates was done with RDI VmDas software, version 1.42.

RD Instruments- Ocean Surveyor 75kHz Vessel mounted ADCP.

¹ Ranges at 1 to 5 knots ship speed are typical and vary with situation.
² Single-ping standard deviation.
³ User's choice of depth cell size is not limited to the typical values specified.

Profile Parameters

• Velocity long-term accuracy (typical): ±1.0%, ±0.5cm/s
• Velocity range: -5 to 9m/s
• # of depth cells: 1 - 128
• Max ping rate: 0.7

Bottom Track

Maximum altitude (precision <2cm/s): 950m

Echo Intensity Profile

Dynamic range: 80dB
Precision: ±1.5dB

Transducer and Hardware

Beam angle: 30°
Configuration: 4-beam phased array
Communications: RS-232 or RS-422 hex-ASCII or binary output at 1200 - 115,200 baud
Output power: 1000W

Standard Sensors

Temperature (mounted on transducer)

• Range: -5° to 45°C
• Precision: ±0.1°C
• Resolution: 0.03°

Environmental

Operating temperature: -5° to 40°C (-5° to 45°C)*
Storage temperature: -30° to 50°C (-30° to 60°C)*

*later instruments have greater range.

Web Page

Further details can be found on the manufacturer's website or in the specification sheet

JR239 75 kHz VMADCP: BODC Processing

The data were received in one Matlab formated file and were converted into BODC internal format following BODC's standard procedures. Tidal model predictions and de-tided data were also provided but have not been loaded as these are subjective calculations, these are available on request. The following table shows how the variables within the Matlab file were mapped to appropriate BODC parameter codes.

All reformatted data were visualised using the in-house Edserplo software, all suspect and null data were flagged as such.

JR239 75 kHz VMADCP: Originator's Data Processing

Sampling Strategy

The vessel mounted 75 kHz RD Instruments Ocean Surveyor ADCP was configured to sample over 70 bins. Five settings were used during the cruise:
1) Narrowband with Bottom Tracking on, maximum bin depth 500 m.
2) Narrowband with Bottom Tracking on, maximum bin depth 1000 m.
3) Narrowband with Bottom Tracking off, maximum bin depth 1000 m.
4) Broadband with Bottom Tracking on, maximum bin depth set to 200 m.
5) Broadband with Bottom Tracking on, maximum bin depth set to 500 m.

The bin size was set to 8 m in broadband and 16 m in narrowband mode and the blanking distance at the surface was set to 8 m. The narrowband mode with and without bottom tracking was mostly used during the cruise. An overview of the available commands to set the ADCP operating parameters and the command files for the narrowband modes to 1000 m used during the cruise can be found in the cruise report page 121.

Originators Data Processing

The ADCP was controlled using the proprietary RDI VmDas software, version 1.42, this was used for; data acquisition, archiving, processing, displaying, and reporting, in addition, a set of Matlab routines were used for the post-processing of the VmDas data. Extensive processing methods can be found in the cruise report page 99 onwards.

To summarise, the ADCP was fed with the navigation and attitude data from the Kongsberg Seatex Seapath 200 GPS system with bad navigation removed. The distance and the direction between navigation fixes were calculated and then converted to distance in eastward and northward direction, and filtered to remove spikes from the navigation. The water and bottom track velocities were scaled and corrected for misalignment, and the horizontal velocities were multiplied by the scaling factor and rotated by the specified misalignment angle. The heading was adjusted by subtracting the misalignment angle. For sequences recorded in bottom track mode, the bottom range was used to blank the data below 86% of the detected bottom depth.

Bad data points from interference, bubbles, outliers etc. were filtered using various criteria:
1) Velocities greater than 1.5 m s^-1.
2) Absolute values of velocity exceeded ±2 times the standard deviation of the error velocity provided through the fourth beam.
3) Velocities outside running average velocity ±2 time standard deviation or running median velocity ± 2 times standard deviation.
4) Changes in ship speed exceeded the maximum ship velocity change of 0.5514 m per ping.
5) Change in heading exceeded the maximum heading velocity change of 10°.
6) The velocities of ping ensembles with the percentage of good four beam solutions equal to zero.

To get usable data, 10 minute averages from the clean, filtered data were calculated taking into account varying bin depths (see the cruise report for details of how averaging was carried out).

Preliminary de-tiding was done for the final 10 minute averages using the tide model 'AntPen'. These data are available on request.

Field Calibrations

The calibration points were extracted using 2 minute averages (see cruise report for details of how the averaging was carried out) of ADCP data meeting the following criteria;
1) Change in ship heading is small.
2) Change in ship speed is small.
3) Ship speed is within the interval average ship speed ± standard deviation.
4) Ship heading is within the interval average ship heading ± standard deviation.
5) Bottom speed is larger than a specified minimum speed.
6) There are a minimum number of possible calibration points in a row that fulfill the criteria.

The calibration was done for the entire cruise using water track calibration. Although bottom track data were collected, most of the cruise took place in deep water, and the available bottom track was not sufficient and so bottom track calibration was not satisfactory.

Misalignment angle (φ): -0.0748
Amplitude (α): 1.015741

Further information on calibration of the VMADCP can be found on page 114 of the cruise report.

Project Information

Antarctic Deep Water Rates of Export (ANDREX) project document

ANDREX is a UK field programme aimed at investigating the role of the Weddell Gyre in the Meridional Overturning Circulation (MOC) and its influence on deep ocean properties.

The MOC is a critical regulator of Earth's climate and is crucial for deep water ventilation across the globe. Surface currents transport waters towards the poles, where they become dense and sink, flowing equatorward as deep, cool currents. The MOC ensures that the deep oceans remain ventilated and conducive to life, and is also important for anthropogenic carbon sequestration. The southern closure of the MOC in the Weddell Sea is strongly influenced by the Weddell Gyre, which facilitates the exchange of waters between the Antarctic Circumpolar Current (ACC) and the waters of the continental shelf. Cooling and sea ice formation in the Weddell Sea lead to overturning of the water column and the ventilation of Antarctic Bottom Water (AABW), which flows out of the Weddell Sea and into the deep oceans to the north. Thus, the Weddell Gyre plays an important role in the properties of deep ocean waters on a global scale.

The goals of ANDREX are to investigate the exchange of water masses between the ACC and the Weddell Sea, including AABW formation and ventilation rates, carbon and nutrient cycling, the influence of fresh water input from sea ice, precipitation and glacial melt, and the role of the Weddell Gyre in anthropogenic carbon sequestration. The project includes hydrographic, ventilation tracer, biogeochemical and bathymetric measurements along the outer rim of the Weddell Gyre.

ANDREX is funded by the UK Natural Environment Research Council (NERC) Antarctic Funding Initiative (AFI) and involves scientists from the National Oceanography Centre, Southampton (NOC), the British Antarctic Survey (BAS), the University of East Anglia (UEA), the University of Manchester, the Alfred Wegener Institut (AWI) and the Woods Hole Oceanographic Institution (WHOI).

For more information please see the official project website at ANDREX

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

WOCE Hydrographic Programme Section A23

This section is part of the One-Time Survey of World Ocean Circulation Experiment (WOCE) designated A23. A hydrographic section from Antarctica to Brazil in the South West Atlantica. A full suite of physical, chemical, biological, meterological and tracer measurements were made. During WOCE in 1995 (James Clark Ross, cruise JR10) the A23 section area encompassed 20-70° S and 20-70° S. Part of this A23 section located in the eastern Scotia Sea has been repeated by theALBATROSS project (James Clark Ross, cruise JR40) in 1999, theUS CLIVAR repeat hydrography/CO₂ in 2005 (R/V Ronald H. Brown, cruise A16S_2005a) under theCLIVAR/Carbon repeat hydrography program. From 2010 onwards the British Antarctic Survey has conducted annual cruises to survey the southern portion of this section, from the Weddell Sea to South Georgia. A comprehensive list of cruises is included below the map.

From

History of Occupations at Section A23

Related Fixed Station activities are detailed in Appendix 1

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:

Appendix 1: WOCE section A23

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.