Metadata Report for BODC Series Reference Number 1840820

• 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

Aanderaa Recording Current Meter Model 9/11

The RCM 9/11 is a family of single-point Doppler recording current meters with different casing options to allow working at depths of up to 300 (RCM 9 LW), 2000 (RCM 9 IW) or 6000 (RCM 11) metres. The recording unit is 51.3 cm or 59.5 cm high (RCM 9 and RCM 11, respectively) with a diameter of 12.8 cm.

The RCM is most commonly deployed in an in-line mooring configuration. As it operates under a tilt up to 35° from vertical, it has a variety of in-line mooring applications by use of surface buoy or sub surface buoy. The instrument is installed in a mooring frame that allows easy installation and removal of the instrument without disassembly of the mooring line. The instrument can also be used for direct reading of the various parameters. This is conveniently done due to its compact design, low drag force and easy handling. Data can be stored internally and read after retrieval or be read in real time on deck by use of the profiling cable.

Meter comprises:

• A Vane Plate (3681) to stabilise the meter during profiling (stops spin).

• Stainless Steel Mooring Frame made to facilitate easy installation and removal of the instrument by use of two knobs.

• Doppler Current Sensor (Current speed sensor) - Range of speed recorded 0-300 cm s^-1 with a 0.3 cm s^-1 resolution.

• Hall Effect Compass - Direction recorded with 0.35 ° resolution, 5 ° for 0.15 ° tilt and 7.5 ° for 15-35 ° tilt.

• Thermistor (Temperature sensor) - With selectable wide, low, high and Arctic ranges. Standard range -2.70 to 21.77 °C, accuracy 0.05 °C, resolution 0.1% of selected range, 63% response time (12 sec).

• Inductive Cell Conductivity Sensor (optional) - Range 0 to 75 mS cm^-1, standard resolution 0.002 mS cm^-1.

• Pressure Sensor (optional) - Silicon piezoresistive bridge, standard range 0 to 3500 kPa, resolution 0.1% of range.

• Turbidity Sensor (optional) - Optical back-scatter sensor, resolution 0.1% of full scale, (RCM 11 depth capacity 2000 m).

• Oxygen Sensor (optional) - Oxygen optode, range 0 to 500 µM, resolution < 1µM, response time 60 sec, depth capacity 6000 m.

• Data storage units DSU 2990 and 2990E are standard data storage devices for Aanderaa data collecting instruments.

A built-in quartz clock allows the time of the first measurement to be recorded in the DSU. The measuring system is made up of a self-balancing bridge with sequential measurement of 10 channels and solid state memory. Channel 1 is a fixed reference reading for control purposes and data identification. Channels 2 and 3 represent measurement of current speed and direction. The direction is found by the use of measurements along two orthogonal axis and linking them to true north by use of an internal compass reading. The instrument can operate continuously or in eight intervals from 1 to 120 minutes. At 60-minute recording interval the operating time is more than two years. The current speed and direction are averaged over the measuring interval. Channels 4, 5 and 6 represent temperature, conductivity and pressure respectively.

Further information can be found in the manufacturer's instrument specification.

BODC Data Processing

Data Processing

The data arrived at BODC as individual .mat files containing data collected on moorings OP1, OP2, OP3, OP4, OP5, OP6, OP7, CI1 and CI2. They were submitted as part of an accession including several different instruments - ADCP, Aquadopp, RCM8, RCM11, RBRsoloT, SBE37 and SBE39.

Reformatting

Parameters in the originator's files were reformatted into an internal file format using BODC standard procedures.

Some variables included in the RCM11 files have not been reformatted into the internal format files, as they will be stored as metadata. These include - botdepth (meters), date, lat (degrees north), lon (degrees east), mooringname, nomdepth (meters), serial_no and type.

The following table lists all the parameters included in the internal format files, showing how the originator's variables as named in the matlab files were mapped to appropriate BODC parameter codes.

No derived parameters were calculated by BODC. Please note that not all parameters are present in all files.

Screening

Quality control flags were automatically added to data outside the expected parameter specific range during the reformatting process. All parameters were then visualised and screened using in house software, and any improbable or missing data point was assigned a quality control flag.

The signal return amplitude 'sigstr' was reformatted for screening purposes only; as it is not an environmental variable, this parameter is not included in the final reformatted files, however it can be retrieved upon request.

During screening of other instruments in OP2 mooring it became clear that it had suffered several knock-downs throughout the deployment period. Data quality does not seem to be affected but caution should be used when analysing the data.

Reference

Fofonoff and Millard (1983). Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science No 44, 53pp.

Originator's Data Processing

Sampling Strategy

Sampling was carried out as part of the BAS LTMS (British Antarctic Survey Long Term Monitoring and Survey) until 2016. From 2016 onwards the moorings are split between 'The Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA)' project and 'Dynamics of the Orkney Passage Outflow (DynOPO)' project.

The projects involve the deployment of moorings CI1, CI2, OP1, OP2, OP3, OP4, OP5, OP6 and OP7 in the Southern Ocean, situated north of Coronation Island and the Orkney Passage in the Weddell and Scotia Sea.

Moorings CI1 and CI2 were deployed from 2005 to 2007 and moorings OP1, OP2, OP3, OP4, OP5 and OP6 have been continuously maintained since 2007 with the addition of OP7 in 2015.

RCM11 data have been collected at 60 minute intervals. Gaps in the series may be caused by either instruments not being recovered, or data not being collected due to instrument malfunction.

Data Processing

Little information is known with regards to the exact details of the calibrations carried out on the mooring data. Data processing, visualisation and calibration were carried out through the use of scripts for Matlab version R2014b produced and ran by the originator.

The originator reported that current direction and velocity components for the 2007 to 2012 data were not corrected for magnetic variation, as at the moorings' sites this is lower than the measurements' accuracy. It was also reported that under some conditions the RCM11s under-read current speeds when compared with a mechanical Vector Measuring Current Meter (VMCM), as indicated by results from Watts et al.. Due to continuing uncertainties regarding which correction would best resolve the different characteristics of these two instruments, the RCM11 measurements were left unmodified by the originator.

Offsets were applied to RCM11 temperature. The values for each deployment/instrument combination is shown in the table below:

No temperature offsets were applied to the RCM11s deployed in 2015.

References

Watts D.R. et al., 2013. Four current meter models compared in strong currents in the Drake Passage. Journal of Atmospheric and Oceanic Technology: 30, 2465-2477. DOI: 10.1175/JTECH-D-13-00032.1

Project Information

BAS Long Term Monitoring and Survey

Introduction

The Long Term Monitoring and Survey project (LTMS) has been running since the British Antarctic Survey (BAS) was created. This project is one of the BAS core projects, with several groups of scientists collecting various types of data e.g biological, geological, atmospheric, among others.

Data collection is achievable through a wide scope of instruments and platforms, e.g. the Antarctic research stations, autonomous instrument platforms deployed on or from BAS research ships, BAS aircrafts, satellite remote sensing and others.

Scientific Objectives

This project was implemented in order to measure change and variability in the Earth system. Its long term duration allows for the monitoring of processes that could be missed in shorter term studies and experiments. The data collected is also used to check and improve the reliability of models used to stimulate and predict the behavior of the Earth system.

The main objectives are:

• Topographic survey
• Geosciences survey
• Biological survey and monitoring
• Atmospheric and oceanographic monitoring

Data Availability

The data sets obtained through this project are available to the academic community.

Data Activity or Cruise Information

Data Activity

Orkney Passage mooring 4 (OP4)

The mooring was deployed at the following positions:

The mooring was deployed on the Orkney Passage on cruise JR20130317 (JR252B, JR272B, JR273A, JR281, UKD-4) on 03 April 2013 and recovery was done on cruise JR20150309 (JR272D, JR310) on 21 March 2015.

The table below lists the instruments deployed on this mooring:

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Orkney Passage OP4 site

Site OP4 is part of the Orkney Passage mooring array which is an activity covered by the Long Term Monitoring and Survey British Antarctic Survey's (BAS) programme. The data collection is the result of an ongoing collaboration between BAS and the Lamont-Doherty Earth Observatory (LDEO).

This site has been occupied since 2011 but throughout the years it has been moved. The recovery/deployment history, including position details, is presented below:

Detailed information for each deployment can be accessed from the OP4 Data Activity document.

Related Fixed Station activities are detailed in Appendix 2

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: OP4

Related series for this Data Activity 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.

Appendix 2: Orkney Passage OP4

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.