Metadata Report for BODC Series Reference Number 1899810

• 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

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 Discovery Cruise DY086 CTD: Instrumentation

CTD Unit and Auxillary Sensors

A Sea-Bird 911plus CTD system was used for 25 of 33 CTD casts on cruise DY086. This was mounted on a 24-way stainless steel rosette frame, equipped with 24 x 20 litre OTE Niskin bottles. The CTD was fitted with the following scientific sensors:

The Data Originator provided BODC with the best data for temperature and salinity.

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.

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

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

RRS Discovery Cruise DY086 CTD Data: BODC Processing

BODC Processing

The CTD data was processed following BODC recommended guidelines, and the processed data was supplied to BODC in an excel spreadsheet with each cast on a different tab. The data were then reformatted to BODC internal NetCDF file format using established procedures.

The Data Originator provided BODC with the best data for temperature and salinity. Originator variables were mapped to appropriate BODC parameter codes for standardisation, and can be seen in the table below:

Following transfer, the data were screened using BODC in-house visualisation software. Suspect data values were assigned the appropriate BODC data quality flag.

The parameter mapping is the same for both the titanium and stainless steel CTDs. The titanium CTD was used during casts 1, 4, 7, 15, 19, 24, 26, and 29.

RRS Discovery Cruise DY086 CTD Data: Originator's Processing

Sampling Strategy

A total of 33 CTD casts were completed during the cruise. The cruise departed the Falkland Islands on November 12, 2017 and returned to the same port on December 19, 2017. Data was collected using a stainless steel CTD with 24 x 20L OTE Niskin bottles for 25 casts, and a titanium CTD with 24 x 10L OTE Niskin bottles for the other 8 casts (casts 1, 4, 7, 15, 19, 24, 26, and 29). For further information on the CTD sampling strategy, please refer to the cruise report.

Originator's Processing

The CTD data was processed following BODC recommended guidelines using standard SBE Data Processing software.

Project Information

Controls over Ocean Mesopelagic Interior Carbon Storage: COMICS

COMICS is a four-year collaborative research project that aims to quantify the flow of carbon in the ocean?s ?twilight? zone in order to accurately model global climate change. This ?twilight? zone is the part of the ocean between 100m and 1000m below the sea surface, where only a small amount of light from the sun can still penetrate.

By investigating carbon dynamics in the ocean interior, COMICS will help to improve predictions of future global climate change.

The COMICS project is led by the National Oceanography Centre and is a collaboration between the British Antarctic Survey and the universities of Queen Mary London, Liverpool, Oxford and Southampton. The project received funding from the Natural Environmental Research Council and runs between April 2017 and 2021.

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: