Metadata Report for BODC Series Reference Number 1179770

• 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

Quality report for FRV Scotia 0312S CTD data

Station 74 - Temperature, salinity and density

At cycles 25 to 45, the profile oscillates back and forth showing a great variability in the range. The cruise report shows that on this day the ship was experiencing strong winds (up to 65 knots). It is believed that the strong winds could have resulted in the sensor moving up and down in the water column, causing the variation witnessed at this station. The values have been flagged by BODC and should be used with caution.

Station 76 - Temperature and conductivity

The data supplied for station 76 were modified by the Originator to remove all conductivity data as they were considered suspect. The first three cycles in the temperature profile were not supplied by the Originator and have been flagged as null values by BODC.

Turbidity and Chlorophyll

Throughout the cruise, turbidity and chlorophyll display large variations in the top few meters. It is believed that these are not real due to the magnitude of the variability and the location of the data. BODC have flagged these values 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

CTD Instrument Description for FRV Scotia 0212S and FRV Scotia 0312S

Sampling Strategy

CTD casts were carried out on cruises FRV Scotia 0212S and FRV Scotia 0312S using the Sea-Bird SBE19plus V2 SEACAT. The instrumentation is detailed below.

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

Sea-Bird SBE 19 and SBE 19plus SEACAT Profiler CTDs

The SBE 19 SEACAT Profiler is a self-contained, battery powered, pumped CTD system designed to measure conductivity, temperature, and pressure in marine or fresh water environments to depths of 10,500 meters. It was replaced by the SBE 19plus model in 2001. An updated version of this instrument is the SBE 19plus V2, which incorporates an electronics upgrade and additional features, with six differentially amplified A/D input channels, one RS-232 data input channel, and 64 MB FLASH memory.

The standard CTD unit comes with a plastic housing (rated to 600 m), although this can be replaced by titanium housing for depths up to 7000 m. It is typically used for CTD profiling although a conversion kit is available for mooring deployments. The CTD can also be attached to an SBE 36 CTD Deck Unit and Power/Data Interface Module (PDIM) for real-time operation on single-core armored cable up to 10,000 m.

Specifications

*Measurements outside this range may be at slightly reduced accuracy due to extrapolation errors.

Options and accessories

Additional sensors can be attached to the CTD, including:

• high accuracy Paroscientific Digiquartz pressure sensor (depth range 0 to 20, 60, 130, 200, 270, 680, 1400, 2000, 4200, 7000 or 10500 m; accuracy 0.02% of full scale; resolution 0.0025% of full scale)
• Dissolved Oxygen (SBE 43 DO Sensor)
• pH* (SBE 18 pH Sensor or SBE 27 pH/ORP Sensor)
• fluorescence
• radiance (PAR)
• light transmission
• optical backscatter (turbidity)

The standard SBE 5M pump may be replaced by an SBE 5P (plastic housing) or 5T (titanium housing) pump for use with dissolved oxygen and/or other pumped sensors. Further details can be found in the manufacturer's SBE 19plus V2 instrument specification or theSBE 19 andSBE 19 plus user guides.

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 0312S CTD Originator's data processing

Sampling Strategy

A total of 63 CTD casts were performed by Marine Scotland as part of ongoing research funded by the Scottish Government, between 20 February 2012 - 9 March 2012 during cruise FRV Scotia 0312S. The CTD casts were deployed throughout the cruise around the west coast of Scotland, Clyde and the north coast of Ireland. The cruise made a port call in Belfast on 28 February 2012, leaving Belfast on 29 February 2012.

A single Knudsen reversing bottle attached to a wire 1 m above the CTD was fired for every cast.

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. 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 63 water samples were taken by Marine Scotland using the Knudsen reversing bottle mentioned above to provide a calibration equation for conductivity as follows:

calibrated conductivity (mS cm^-1) = measured conductivity x 1.001246 - 0.081408.

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.

Fluorescence

Marine Scotland carried out a check using CTD data from a prior cruise where the CTD was used to look for any noticeable change in the sensors performance and concluded that no calibration were needed for the fluorescence data.

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 0212S, 0312S, 0812S,0912S, 1112S,1412S and 1612S CTD data

The data arrived at BODC in 7 concatenated ASCII format files representing cruises FRV Scotia 0212S (56 casts), 0312S (63 casts), 0812S (41 casts), 0912S (85 casts), 1112S (20 casts), 1412S (4 casts) and 1612S (55 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.

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: