Metadata Report for BODC Series Reference Number 714899
No Problem Report Found in the Database
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."
CTD Unit and Auxiliary Sensors
A Sea-Bird Electronics SBE 917 plus CTD unit was used. The CTD unit included the following sensors.
|Sensor||Manufacturer||Serial number||Calibration date|
|PAR (downwards facing)||Chelsea||46071||2002-07-02|
|PAR (upwards facing)||Chelsea||46072||2002-07-02|
Independent salinity samples were used to calibrate the CTD conductivity data. The following calibration values were supplied to BODC, who applied them to the data as part of the transfer process.
|Parameter||Value of m (y=mx+c)||Value of c (y=mx+c)||Equation|
|Conductivity||1.006431||-0.231817||C(cal) = 1.006431C(obs) - 0.231817|
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.
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.
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 for the SBE 9 plus underwater unit are listed below:
|Parameter||Range||Initial accuracy||Resolution at 24 Hz||Response time|
|Temperature||-5 to 35°C||0.001°C||0.0002°C||0.065 sec|
|Conductivity||0 to 7 S m-1||0.0003 S m-1||0.00004 S m-1||0.065 sec (pumped)|
|Pressure||0 to full scale (1400, 2000, 4200, 6800 or 10500 m)||0.015% of full scale||0.001% of full scale||0.015 sec|
Further details can be found in the manufacturer's specification sheet.
Seapoint Chlorophyll Fluorometer
The Seapoint Chlorophyll Fluorometer (SCF) is a low power instrument for in situ measurements of chlorophyll a. The SCF uses modulated blue LED lamps and a blue excitation filter to excite chlorophyll a. The fluorescent light emitted by the chlorophyll a passes through a red emission filter and is detected by a silicon photodiode. The low level signal is then processed using synchronous demodulation circuitry which generates an output voltage proportional to chlorophyll a concentration. The SCF may be operated with or without a pump.
Sensor specifications, current at August 2006, are given in the table below. More information can be found at the manufacturer's web site.
|Power requirements||8 - 20 VDC, 15 mA avg., 27 mA pk.|
|Output||0 - 5.0 VDC|
|Output Time Constant||0.1 sec.|
|Power-up transient period||< 1 sec.|
|Excitation Wavelength||470 nm CWL, 30 nm FWHM|
|Emission Wavelength||685 nm CWL, 30 nm FWHM|
|Sensing Volume||340 mm3|
|Minimum Detectable Level||0.02 µg l-1|
|Gain||Sensitivity, V µg-1 l-1||Range, µg l-1|
Chelsea Technologies Photosynthetically Active Radiation (PAR) Irradiance Sensor
This sensor was originally designed to assist the study of marine photosynthesis. With the use of logarithmic amplication, the sensor covers a range of 6 orders of magnitude, which avoids setting up the sensor range for the expected signal level for different ambient conditions.
The sensor consists of a hollow PTFE 2-pi collector supported by a clear acetal dome diverting light to a filter and photodiode from which a cosine response is obtained. The sensor can be used in moorings, profiling or deployed in towed vehicles and can measure both upwelling and downwelling light.
|Operation depth||1000 m|
|Range||2000 to 0.002 µE m-2 s-1|
|Angular Detection Range||± 130° from normal incidence|
|Relative Spectral Sensitivity|| |
flat to ± 3% from 450 to 700 nm
down 8% of 400 nm and 36% at 350 nm
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.
|Pathlength||10 or 25 cm|
|Wavelength||370, 470, 530 or 660 nm|
~ 20 nm for wavelengths of 470, 530 and 660 nm
~ 10 to 12 nm for a wavelength of 370 nm
|Temperature error||0.02 % full scale °C-1|
|Temperature range||0 to 30°C|
|Rated depth|| |
600 m (plastic housing)
6000 m (aluminum housing)
Data were received by BODC in one ASCII format file that was subsequently split into seven separate files, one for each CTD profile. The series were reformatted to the internal QXF format using BODC transfer function 340. The following table details the mapping of variables to BODC parameter codes.
|Original parameter name||Original Units||Description||BODC Parameter Code||BODC Units||Comments|
|Pressure||Decibars||Pressure exerted by the water column||PRESPR01||Decibars|
|Temperature||°C||Temperature of the water column||TEMPST01||°C|
|Conductivity||mS cm-1||Electrical conductivity of the water column||CNDCST01||S m-1||Conversion by transfer (mS cm-1 x 0.1)|
|Salinity||Dimensionless||Practical salinity of the water column by CTD and computation using UNESCO 1983 algorithm||PSALST01||Dimensionless|
|Fluorescence||µg l-1||In-situ fluorescence||CPHLPM01||mg m-3|
|Beam attenuation||m-1||Attenuance of the water column||ATTNZS01||m-1|
|Downwelling PAR||Volts||Instrument output (voltage) by PML/Chelsea Instruments 2-pi PAR downwelling light meter||LVLTPD01||Volts|
|Upwelling PAR||Volts||Instrument output (voltage) by PML/Chelsea Instruments 2-pi PAR upwelling light meter||LVLTPU01||Volts|
Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO. Any data considered as suspect were flagged 'M'. Flags from the originator marking suspect data were retained during transfer and flagged 'L'.
Originator's Data Processing
The raw CTD data files were processed through the SeaBird Electronics SeaSoft data processing software following standard procedures. The originators used in-house interactive visual display editing software to edit out individual spikes in the primary temperature and conductivity channels. An ASCII file was generated for each CTD cast and all files from a cruise were concatenated into one ASCII file which was submitted to BODC.
No Project Information held for the Series
|Principal Scientist(s)||Philip J Copland (Fisheries Research Services Aberdeen Marine Laboratory)|
Complete Cruise Metadata Report is available here
No Fixed Station Information held for the Series
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|<||Below detection limit|
|>||In excess of quoted value|
|A||Taxonomic flag for affinis (aff.)|
|B||Beginning of CTD Down/Up Cast|
|C||Taxonomic flag for confer (cf.)|
|E||End of CTD Down/Up Cast|
|G||Non-taxonomic biological characteristic uncertainty|
|I||Taxonomic flag for single species (sp.)|
|K||Improbable value - unknown quality control source|
|L||Improbable value - originator's quality control|
|M||Improbable value - BODC quality control|
|O||Improbable value - user quality control|
|0||no quality control|
|2||probably good value|
|3||probably bad value|
|6||value below detection|
|7||value in excess|
|A||value phenomenon uncertain|
|Q||value below limit of quantification|