Metadata Report for BODC Series Reference Number 1906421

• 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 quality report for CTD deployments by Marine Scotland Science during 2016

Data have been through thorough quality control checks conducted by Marine Scotland Science (MSS) and any quality control flags applied by MSS have been applied to the data during BODC processing. Additionally, improbable flags ('M') were applied to any derived parameters where MSS flagged a value as '3 = probably bad data' (SeaDataNet quality flags were used by MSS) in a channel used in the derivation. An interpolated flag ('T') was also added to derived values where MSS flagged the value as interpolated in the channel used in the derivation.

In addition to MSS quality checks, data were screened by BODC using in house visualisation software during BODC processing. During BODC screening an outlier in series 1908396 was found in the CPHLPR01 and CPHLPS01 channels. The outlier was flagged 'M' as the values in both CPHLPR01 and CPHLPS01 were approximately 10 times higher than the rest of the profile.

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

Instrumentation used for CTD deployments by Marine Scotland Science during 2016

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.

WETLabs ECO FLNTU fluorescence and turbidity sensor

The Environmental Characterization Optics (ECO) Fluorometer and Turbidity (FLNTU) sensor is a dual wavelength, single-angle instrument that simultaneously determines chlorophyll fluorescence and turbidity. It is easily integrated in CTD packages and provides a reliable turbidity measurement that is not affected by Colored Dissolved Organic Matter (CDOM) concentration.

The FLNTU can operate continuously or periodically and has two different types of connectors to output the data. There are 5 other models that operate the same way as this instrument but have slight differences, as stated below:

• FLNTU(RT) - has an analog an RS-232 serial output and operates continuously, when power is supplied
• FLNTU(RT)D - similar to the FLNTU(RT) but has a depth rating of 6000 m
• FLNTUB - has internal batteries for autonomous operation
• FLNTUS - has an integrated anti-fouling bio-wiper
• FLNTUSB - has the same characteristics as the FLNTUS but with internal batteries for autonomous operation

Specifications

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

WETLabs ECO-FL Fluorometer

The Environmental Characterization Optics series of single channel fluorometers are designed to measure concentrations of natural and synthetic substances in water, and are therefore useful for biological monitoring and dye trace studies. Selected excitation and emission filters allow detection of the following substances: chlorophyll-a, coloured dissolved organic matter (CDOM), uranine (fluorescein), rhodamine, phycoerythrin and phycocyanin.

The ECO-FL can operate continuously or periodically and has two different types of connectors to output the data (analogue and RS-232 serial output). The potted optics block results in long term stability of the instrument and the optional anti-biofouling technology delivers truly long term field measurements.

In addition to the standard model, five variants are available, and the differences between these and the basic ECO-FL are listed below:

• FL(RT): similar to the FL but operates continuously when power is supplied
• FL(RT)D: similar model to the (RT) but has a depth rating of 6000 m
• FLB: includes internal batteries for autonomous operation and periodic sampling
• FLS: similar to FLB but has an integrated anti-fouling bio-wiper
• FLSB: similar to the FLS, but includes internal batteries for autonomous operation

Specifications

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

BODC Processing of Marine Scotland Science CTD deployments during 2016

Data Processing

Data were submitted to BODC as 12 ASCII files by email and following BODC procedures the data were archived. The data from all cruises in 2016, with the expection of 0216S, were accompanied by a file of quality control flags. During BODC proccessing these flags were applied to the data. The header of each file contained the type of CTD used for each cruise, the sensors on the CTD and their serial numbers, an explanation of the format of the file and details of any calibrations.

The concatenated files were sub-divided into individual files for each cast using in house BODC Matlab software. The divided files were then transferred to BODC internal format using standard BODC processing procedures. The originator's variables were mapped to BODC parameter codes as follows:

Channels that were not transferred are available on request.

Screening

Post transfer analysis and crosschecks were applied according to BODC procedures. This involved the screening of data using BODC's in house visualisation software where any suspect data were flagged but not removed. During screening it was also checked that the originator's flags had been applied to the data correctly.

References

Benson B.B. and Krause D., 1984. The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnol. Oceanogr., 29(3), 620-632.

Fofonoff N.P. and Millard R.C., 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science No. 44, 53pp.

Originator Processing of Marine Scotland Science CTD deployments during 2016

Sampling Strategy

During 2016 a number of Marine Scotland cruises occurred on the FRV Scotia and FRV Alba Na Mara where objectives covered trawl sampling, fish sampling, acoustic surveys and hydrographic sampling. As part of the hydrographic sampling numerous CTD casts were completed on each cruise. The time channel of these casts was recorded in GMT.

Data Processing

The CTD data were processed by Marine Scotland using the Sea-Bird SeaSoft routines as recommended in the SeaSoft manual for model type Sea-Bird SBE19plus V2 SEACAT.

Pressure data were binned to 1 dbar using SeaSoft and the primary temperature and conductivity channels were adjusted to produce 'edit' channels. Marine Scotland regards the 'edit' channels as the definitive version of the data.

The adjustments consisted of a de-spiking process using Marine Scotland in-house visualisation software and, as necessary, application of a low pass filter as described in Sy (1985).

Field Calibrations

For a number of the cruises Marine Scotland used water samples collected during the CTD casts to generate a calibration equations for the conductivity and fluorescence channels. These calibrations were not applied to the raw data by the originator but were supplied as metadata. The available calibrations are as follows:

Conductivity

Fluorescence

Reference

Sy A., 1985. An alternative editing technique for oceanographic data. Deep Sea Research, 32 (12), 1591-1599.

Project Information

No Project Information held for the Series

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: