Metadata Report for BODC Series Reference Number 1185486

• 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

Turbidity

The turbidity value is constant throughout the profile at ~9.76 NTU for stations 631 to 665 inclusively and for station 667. The Originator has confirmed that these data are to be treated as suspect and have been flagged.

Quality report for FRV Scotia 1712S

Turbidity

The Originator has informed BODC that values of 0.000 NTU in the turbidity profile should be considered suspect. BODC has flagged these values where they occur within this cruise.

Throughout the cruise there are instances where either the first or the top two cycles in the turbidity profile show a greater variability in range when compared to the rest of the profile and neighbouring stations. These cycles have been flagged by BODC as suspect.

Station 667 - chlorophyll

The chlorophyll values for this station are a factor of 10 higher than those measured on previous or subsequent stations. The Originator has informed BODC that these values are suspect and were caused by either the cap being left on the sensor or something obstructing the sensor. These data have been flagged as suspicious.

Data Access Policy

Public domain 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.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

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.

CTD Instrument Description for FRV Scotia 1312S and FRV Scotia 1712S

Sampling Strategy

CTD casts were carried out on cruises FRV Scotia 1312S and FRV Scotia 1712S using the Sea-Bird SBE911plus. The instrumentation is detailed below.

No changes to the CTD instrumentation were recorded during these cruises.

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.

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.

BODC CTD Screening

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

• Irregularities such as infeasible values
• Inconsistencies between related information. For example:
  • Deepest CTD data cycle is significantly greater than the depth of the sea floor.
  • Times of the cruise and the start/end of the data series.
  • Length of the record, number of data cycles, cycle interval, clock error and the period over which data were collected.
  • Parameters stated as measured and the parameters actually present in the data series.
• Originator's comments on instrument/sampling device performance and data quality.

Documents are written by BODC highlighting irregularities that cannot be resolved.

Data cycles are inspected using depth series plots of all parameters. These presentations undergo screening to detect infeasible values within the data cycles themselves and inconsistencies when comparing adjacent data sets displaced with respect to depth, position or time.

Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value.

The following types of irregularity, each relying on visual detection in the time series plot, are amongst those that may be flagged as suspect:

• Spurious data at the start or end of the record where the instrument was recording in air
• Obvious spikes occurring in the data due electrical problems
• Constant, or near-constant, data channels

If a large percentage of the data is affected by irregularities, deemed abnormal, then instead of flagging the individual suspect values, a caution may be documented.

The following types of inconsistency are detected automatically by software:

• Data points with values outside the expected range for the parameter, as defined by the BODC parameter usage vocabulary.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought, and where necessary, documented. This covers inconsistencies in the following:

• Maximum and minimum values of parameters (spikes excluded).
• Anomalous readings due to the CTD package being bounced through temperature and/or salinity gradients.

This screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC's making are not introduced.

FRV Scotia 1712S CTD Originator's data processing

Sampling Strategy

A total of 119 CTD casts were performed by Marine Scotland as part of on going research funded by the Scottish Government, during cruise FRV Scotia 1712S. Trial casts were deployed east of Stonehaven, Aberdeen in the North Sea on 7 December 2012 prior to the cruise travelling to the JONSIS long term monitoring section off the north coast of Orkney. The cruise then travelled to the Fair Isle- Munken and Nolso-Flugga long term monitoring sections all located between the Faroe Islands and the north coast of Scotland. The last cast was taken on 18 December 2012 before returning to Aberdeen on 21 December 2012.

A SBE35 carousel was used to collect all water samples.

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 911plus V2 SEACAT. Pressure data were binned to 1 dbar using SeaSoft. The primary temperature and conductivity channels were adjusted to produce 'edit' channels which Marine Scotland regards 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). The time was recorded in UTC.

Field Calibrations

Conductivity

A total of 142 water samples were taken by Marine Scotland using a SBE35 carousel to provide a calibration equation for conductivity as follows:

Calibrated conductivity (mS cm^-1) = measured conductivity x 0.999686 + 0.011023.

The calibration was not applied to the data by the Originator.

Fluorescence

A total of 116 water samples were taken by Marine Scotland using a SBE35 carousel to provide a calibration equation for fluorescence as follows:

Calibrated fluorescence (µg l^-1) = measured fluorescence x 0.000443 + 0.028230.

The calibration was not applied to the data by the Originator.

Temperature

Marine Scotland examined the latest and the previous manufacturer's calibrations to look at the differences in the temperature recorded. There were no significant differences and therefore Marine Scotland concluded that no further calibrations needed to be undertaken.

Reference

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

Processing by BODC of FRV Scotia cruises 0512S, 1312S and 1712S CTD data

The data arrived at BODC in 3 concatenated ASCII format files representing cruises FRV Scotia 0512S (97 casts) , 1312S (125 casts) and 1712S (119 casts). The concatenated files were sub-divided into individual files for each cast, using BODC in house Matlab software. These were reformatted to the internal BODC format using transfer function 340. The following table shows how the variables within the files were mapped to appropriate BODC parameter codes:

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag.

Reference

Fofonoff, P., Millard Jr, R.C., 1983. Algorithms for computation of fundamental properties of seawater.Unesco Technical Papers in Marine Sciences 44, 53 pp.

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

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: