Metadata Report for BODC Series Reference Number 1814075

• 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

RRS James Clark Ross JR20150309 (JR272D, JR310) CTD Data: Quality Report

The originator noted that the CTD sampling was largely a success. There was a constant struggle to keep the sensors from freezing up during recovery and deployment of some CTDs, therefore conductivity drift appeared to increase following a spell of very cold weather.

Transmittance (POPTDR01) channels were flagged suspect by BODC where values were outside the parameter range (0-100%) or contained data spikes. This may be due to a suspect manufacturer's calibration or other reasons BODC are unaware of and should therefore be used with caution.

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

Sea-Bird Dissolved Oxygen Sensor SBE 43 and SBE 43F

The SBE 43 is a dissolved oxygen sensor designed for marine applications. It incorporates a high-performance Clark polarographic membrane with a pump that continuously plumbs water through it, preventing algal growth and the development of anoxic conditions when the sensor is taking measurements.

Two configurations are available: SBE 43 produces a voltage output and can be incorporated with any Sea-Bird CTD that accepts input from a 0-5 volt auxiliary sensor, while the SBE 43F produces a frequency output and can be integrated with an SBE 52-MP (Moored Profiler CTD) or used for OEM applications. The specifications below are common to both.

Specifications

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

RRS James Clark Ross JR20150309 (JR272D, JR310) CTD Instrumentation

A Sea-Bird 911 plus CTD system was used on cruise JR20150309 (JR272D, JR310). This was mounted on a SBE-32 carousel water sampler holding 24 12-litre Niskin bottles. The CTD was fitted with the following scientific sensors:

A single Teledyne RDI 300kHz Workhorse Monitor direct-reading ADCP was also fitted to the CTD frame.

Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers

The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.

Underwater unit

The CTD underwater unit (SBE 9 or SBE 9 plus) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus, that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.

Temperature, conductivity and pressure sensors

The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.

The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

Additional sensors

Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.

Deck unit or SEARAM

Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus.

Specifications

Specifications for the SBE 9 plus underwater unit are listed below:

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

SeaBird SBE35 Deep Ocean Standards Thermometer

The SBE 35 is a high precision thermometer that can be used in fixed point cells or at depths up to 6800 m. It is not affected by shock and vibration, allowing it to be used in calibration laboratories and for thermodynamic measurement of hydro turbine efficiency.

The SBE35 can be used with the SBE32 Carousel Water Sampler and with a real-time or autonomous CTD system. In this case, an SBE35 temperature measurement is collected each time a bottle is fired and the value is stored in EEPROM (Electrically Erasable Programmable Read-Only Memory), eliminating the need for reversing thermometers while providing a high accuracy temperature reading.

The SBE35 is standardized in water triple point (0.0100 °C) and gallium melting point (29.7646 °C) cells, following the methodology applied to the Standard-Grade Platinum Resistance Thermometer (SPRT). However, it does not need a resistance bridge, making it more cost-efficient than an SPRT.

Temperature is determined by applying an AC excitation to reference resistances and an ultrastable aged thermistor. Each of the resulting outputs is digitized by a 20-bit A/D converter. The AC excitation and ratiometric comparison uses a common processing channel, which removes measurement errors due to parasitic thermocouples, offset voltages, leakage currents and gain errors.

Specifications

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

Chelsea Technologies Group Aquatracka MKIII fluorometer

The Chelsea Technologies Group Aquatracka MKIII is a logarithmic response fluorometer. Filters are available to enable the instrument to measure chlorophyll, rhodamine, fluorescein and turbidity.

It uses a pulsed (5.5 Hz) xenon light source discharging along two signal paths to eliminate variations in the flashlamp intensity. The reference path measures the intensity of the light source whilst the signal path measures the intensity of the light emitted from the specimen under test. The reference signal and the emitted light signals are then applied to a ratiometric circuit. In this circuit, the ratio of returned signal to reference signal is computed and scaled logarithmically to achieve a wide dynamic range. The logarithmic conversion accuracy is maintained at better than one percent of the reading over the full output range of the instrument.

Two variants of the instrument are available, both manufactured in titanium, capable of operating in depths from shallow water down to 2000 m and 6000 m respectively. The optical characteristics of the instrument in its different detection modes are visible below:

* The wavelengths for the turbidity filters are customer selectable but must be in the range 400 to 700 nm. The same wavelength is used in the excitation path and the emission path.

The instrument measures chlorophyll a, rhodamine and fluorescein with a concentration range of 0.01 µg l^-1 to 100 µg l^-1. The concentration range for turbidity is 0.01 to 100 FTU (other wavelengths are available on request).

The instrument accuracy is ± 0.02 µg l^-1 (or ± 3% of the reading, whichever is greater) for chlorophyll a, rhodamine and fluorescein. The accuracy for turbidity, over a 0 - 10 FTU range, is ± 0.02 FTU (or ± 3% of the reading, whichever is greater).

Further details are available from the Aquatracka MKIII specification sheet.

Biospherical Instruments QCP-2200 [underwater] PAR sensor

A cosine-corrected PAR quantum irradiance profiling sensor. For use in underwater applications with a 16 bit or higher analog-to-digital converter. Measures light available for photosynthesis on a flat surface. Operation is by a linear analog output voltage that is proportional to the log of incident PAR (400-700 nm) irradiance. The sensor is designed for operation in waters to depths of up to 2,000 m (standard) or 6,800 m (high-pressure standard option) or 10,000 m (high-pressure user-specific option).

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/Biospherical_QCP_2000_series_brochure.pdf

Tritech Digital Precision Altimeter PA200

This altimeter is a sonar ranging device that gives the height above the sea bed when mounted vertically. When mounted in any other attitude the sensor provides a subsea distance. It can be configured to operate on its own or under control from an external unit and can be supplied with simultaneous analogue and digital outputs, allowing them to interface to PC devices, data loggers, telemetry systems and multiplexers.

These instruments can be supplied with different housings, stainless steel, plastic and aluminum, which will limit the depth rating. There are three models available: the PA200-20S, PA200-10L and the PA500-6S, whose transducer options differ slightly.

Specifications

Common specifications are presented below

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

WETLabs C-Star transmissometer

This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.

Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.

This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.

Specifications

Further details are available in the manufacturer's specification sheet or user guide.

RRS James Clark Ross JR20150309 (JR272D, JR310) CTD Data: BODC Processing

The processed data files were submitted as mstar .nc files. Each file contained data for the following parameters: pressure; temperature; conductivity; oxygen; transmittance; fluorescence; PAR; salinity; and density. Additional deployment metadata such as time, latitude and longitude were also included.

The final processed mstar files were reformatted by transferring only relevant parameters and mapping to standardised BODC Parameter codes into an internal NetCDF file.

The following table shows the mapping of the originator variables to the appropriate BODC parameter codes:

As part of standard BODC procedure, we do not transfer derived parameters submitted by the originator due to the uncertainty of the calculations used.

BODC re-derive these parameters using standard algorithms. PSALST01/PSALST02 have not been re-derived as we are confident the standard algorithm of PSS78 has been used. Potential Temperature (POTMCV01), sigma-theta (SIGTPR01) and oxygen saturation (OXYSZZ01) have been re-derived and transferred to the internal NetCDF file.

Screening of data files were then completed using in-house software EDSERPLO, which allows a visual inspection to take place of the data values and to flag any missing data or obvious spikes in the data.

Please note the original data submitted to BODC can be made available on request.

RRS James Clark Ross JR20150309 (JR272D, JR310) CTD Data: Originator Processing

Originator's Sampling

A total of 74 CTDs were deployed at various stations for different project elements which include: recoevery and redeployment of BAS/LDEO moorings in the northwestern Weddell Sea and in Orkney Passage; deployment of further instruments and an additional mooring in support of the DynOPO project; and A23 repeat hydrographic section from the Weddell Sea to South Georgia.

Further details about the specific instrumentation attached to the CTD for this cruise can be found in the CTD Instrument document.

Data logging started once the CTD had left the deck and all hands were off. The deployment procedure was to lower the CTD, stopping at 10 m wire out, where the rosette was left until conductivity-activated pumps turned on and the sensors were equilibrated with ambient conditions.

The pumps are typically expected to switch on 60 seconds after the instrument is deployed. We used the CTD in waters close to freezing point and air temperature well below zero. Here we saw that on many occasions the pumps took several minutes to turn on and the sensors (predominately conductivity) were very slow to equilibrate. The cause of this is thought to be linked to the air temperatures during deployment, despite the short time (minutes) between heated storage and immersion.

After the soak, the CTD was raised to 5 m, or as close to the surface as wave and swell condition allowed, and then lowered to within 20 m of the seabed. The altimeter began reading at 100 m above the seabed and was used to determine when to stop the payout of the wire. Bottles were fired at the bottom and on the upcast, where the procedure was to stop the CTD winch, hold the package in situ for 30 seconds to one minute to allow sensors to equilibrate, and then fire a bottle. Bottle sampling depths were chosen based on low vertical salinity gradients seen during the downcast. These included the bottom, the mixed layer and a few other depths. Salinity samples from these depths were used to calibrate the CTD conductivity and salinity. In order to let the SBE-35 standard thermometer acquire the required 8 readings for a mean temperature, there was a gap of 30 seconds or more between each firing.

Originator's Processing

Data were collected using Seabird Electronics Seasave software. Initial post-processing of the data was completed in SBE Data Processing and further processing in Matlab was completed using the mstar processing suite, developed at NOCS.

Seabird processing

Data were recorded and viewed using Seasave version 7.22.3. For each cast 4 files were created:

• jr310_XXX.hex - hexadecimal (raw) ascii data file
• jr310_XXX.XMLCON - ascii configuration file with calibration information
• jr310_XXX.hdr - ascii header file containing sensor information
• jr310_XXX.bl - ascii file containing bottle fire information

After every deployment a batch script was run to copy the raw data to the network drives and do some preliminary processing with SBE Data Processing version 7.22.2. This included creating a sound velocity profile for updating the EM122 and a coarser resolution copy of the data for sending to the Met Office. Once data have been backed up to the network drive, the .hex file is passed through the Align CTD and Cell Thermal Mass modules of SBE Data Processing. Align CTD offsets for temporal offsets between the sensors on the CTD; in this case, the oxygen measurements were advanced by five seconds. Cell thermal mass corrects for the effects of conductivity cell thermal mass from the measured conductivity. Once complete the following three files were transferred to the network drive.

• JR310_XXX_align_ctm.cnv - .cnv file, align ctd and cell thermal mass
• JR310_XXX_align.cnv - .cnv file, align ctd.
• JR310_XXX.cnv - .cnv file, no adjustment

SBE-35 high precision thermometer

Data from the SBE-35 were uploaded using Seaterm version 1.59. Once the data had been uploaded the sample history was cleared and checks were made to ensure that the sample numbers matched the log records for each cast. The process batch script transferred across the file and its nomenclature was: JR310_XXX_sbe35.asc. More information on the SBE-35 is found in the CTD calibration section of the cruise report.

Mstar processing

CTD data were processed using the mstar Matlab scripts written by Brian King at NOCS. A detailed summary of mstar proccessing used on this cruise can be found in the cruise report.

Calibrations

Details of specific calibrations can be found in the cruise report.

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

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Orkney Passage OP2 site

Site OP2 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 2007 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 OP2 Data Activity document.

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: Orkney Passage OP2

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.