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Metadata Report for BODC Series Reference Number 1070289

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
Sea-Bird SBE 911plus CTD  CTD; water temperature sensor; salinity sensor
Biospherical QSP-200L underwater PAR  radiometers
WETLabs WETStar fluorometer  fluorometers
WETLabs C-Star transmissometer  transmissometers
Paroscientific 410K Pressure Transducer  water temperature sensor; water pressure sensors
Sea-Bird SBE 3plus (SBE 3P) temperature sensor  water temperature sensor
Sea-Bird SBE 4C conductivity sensor  salinity sensor
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Prof Jim Aiken
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Atlantic Meridional Transect (AMT)

Data Identifiers

Originator's Identifier AMT7007
BODC Series Reference 1070289

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1998-09-26 10:15
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars

Spatial Co-ordinates

Latitude 30.06417 N ( 30° 3.9' N )
Longitude 19.94583 W ( 19° 56.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth 2.48 m
Maximum Sensor or Sampling Depth 204.0 m
Minimum Sensor or Sampling Height 4460.7 m
Maximum Sensor or Sampling Height 4662.22 m
Sea Floor Depth 4664.7 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface


BODC CODERankUnitsTitle
ATTNMS011per metreAttenuation (red light wavelength) per unit length of the water body by WET Labs 25cm path length transmissometer and calibration to read zero in clear water
CPHLPS011Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by in-situ chlorophyll fluorometer and calibration against sample data
FVLTWS011VoltsRaw signal (voltage) of instrument output by linear-response chlorophyll fluorometer
IRRDPP011MicroEinsteins per square metre per secondDownwelling 2-pi scalar irradiance as photons of electromagnetic radiation (PAR wavelengths) in the water body by 2-pi scalar radiometer
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALCU011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm and NO calibration against independent measurements
SIGTPR011Kilograms per cubic metreSigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
TEMPCU011Degrees CelsiusTemperature of the water body by CTD and NO verification against independent measurements

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

RSS Discovery Cruise AMT7 CTD Data Quality Document

Downwelling sub-surface PAR irradiance

For downwelling PAR, some data points were beyond the maximum range of the parameter and so were flagged as suspect. There are no irradiance data for casts AMT7023 and AMT7029 to AMT7033.

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

James Clark Ross Cruise AMT7 CTD Instrumentation

Sea-Bird Electronics 911plus CTD (with SBE9 CTD and SBE11 deck unit)
Fitted with secondary conductivity cell and temperature sensor
Rosette fitted with 12 30-litre Niskin water bottles
Wet Labs WETstar miniature fluorometer model 9707005, SN WS3S-303P
Wet Labs Cstar transmissometer model 9706011, SN CST-153R
Biospherical Instruments Inc. spherical PAR sensor model QSP-200L, SN4499

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 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.

WET Labs WETStar Fluorometers

WET Labs WETStar fluorometers are miniature flow-through fluorometers, designed to measure relative concentrations of chlorophyll, CDOM, uranine, rhodamineWT dye, or phycoerythrin pigment in a sample of water. The sample is pumped through a quartz tube, and excited by a light source tuned to the fluorescence characteristics of the object substance. A photodiode detector measures the portion of the excitation energy that is emitted as fluorescence.


By model:

  Chlorophyll WETStar CDOM WETStar Uranine WETStar Rhodamine WETStar Phycoerythrin WETStar
Excitation wavelength 460 nm 370 nm 485 nm 470 nm 525 nm
Emission wavelength 695 nm 460 nm 530 nm 590 nm 575 nm
Sensitivity 0.03 µg l-1 0.100 ppb QSD 1 µg l-1 - -
Range 0.03-75 µg l-1 0-100 ppb; 0-250 ppb 0-4000 µg l-1 - -

All models:

Temperature range 0-30°C
Depth rating 600 m
Response time 0.17 s analogue; 0.125 s digital
Output 0-5 VDC analogue; 0-4095 counts digital

Further details can be found in the manufacturer's specification sheet, and in the instrument manual.

Biospherical Instruments Quantum Scalar Irradiance Profiling Sensor QSP-200

The QSP-200 is a submersible spherical radiance collector designed to ensure a uniform directional response over 3.7-pi steradians. The aluminium-encased optical light pipe funnels flux from the collector to a silicon photodetector that has a flat quantum response over the Photosynthetically Active Radiation (PAR) spectrum (400 - 700 nm).

The sensor can be coupled with other instruments and accessories, allowing for automatic data acquisition and digital display. The standard version has a depth rating of 1000 m and the QSP-200D includes the option of a 200 m depth transducer. The logarithmic output version (QSP-200L4S) is available for integration with CTD or STD and uses a shielded underwater cable. The QSP-200 has been superseded by the QSP-2300.


Wavelength 400 to 700 nm
PAR Spectral Response better than ± 8% within the specified wavelength
Directional response ± 6% for 0 to 110°
PAR Dynamic Range 1.4 x 10-5 to 0.5 µE cm-2 s-1
Nominal sensitivity 1 V = 1 x 1017 quanta cm-2 sec-1
Noise level < 1 mV
Maximum Noise Sensor Dark < 100 µV RMS
Response Temperature Coefficient < 0.15% °C-1
Temperature Range -2 to 35°C
Temperature coefficient of the dark signal < 10 µV °C-1
Depth rating 1000 m

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

Paroscientific Absolute Pressure Transducers Series 3000 and 4000

Paroscientific Series 3000 and 4000 pressure transducers use a Digiquartz pressure sensor to provide high accuracy and precision data. The sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

The 3000 series of transducers includes one model, the 31K-101, whereas the 4000 series includes several models, listed in the table below. All transducers exhibit repeatability of better than ±0.01% full pressure scale, hysteresis of better than ±0.02% full scale and acceleration sensitivity of ±0.008% full scale /g (three axis average). Pressure resolution is better than 0.0001% and accuracy is typically 0.01% over a broad range of temperatures.

Differences between the models lie in their pressure and operating temperature ranges, as detailed below:

Model Max. pressure (psia) Max. pressure (MPa) Temperature range (°C)
31K-101 1000 6.9 -54 to 107
42K-101 2000 13.8 0 to 125
43K-101 3000 20.7 0 to 125
46K-101 6000 41.4 0 to 125
410K-101 10000 68.9 0 to 125
415K-101 15000 103 0 to 50
420K-101 20000 138 0 to 50
430K-101 30000 207 0 to 50
440K-101 40000 276 0 to 50

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)

Further details are available in the manufacturer's specification sheet or user guide.

James Clark Ross Cruise AMT7 CTD Processing

Originator's Processing

The CTD profiles were processed onboard using Sea-Bird's data processing software.

BODC data processing

  • Reformatting

    The data files were sent to BODC in Sea-Bird's data processing software output. All available channels were listed into ASCII format. Non-null channels were then converted to PXF, a BODC internal format. The data were processed from 1Hz averaged down- and upcast data. Sigma-theta was calculated and output from the raw data during the conversion to PXF format.


    Originator's Parameter Originator's Units Description BODC code BODC Units Comments
    Depth m Pressure PRESPR01 decibars Converted from depth to pressure during transfer to PXF
    Temperature °C Temperature TEMPCU01 °C -
    Temperature, 2 °C Temperature TEMPCU02 °C -
    Salinity - Salinity PSALCU01 - -
    Salinity, 2 - Salinity PSALCU02 - -
    Voltage 0 V Beam attenuation ATTNMS01 m-1 Calibrated to zero in clear water
    Voltage 1 V Fluorometer voltage FVLTWS01 V -
    Voltage 2 V 2 pi-PAR meter voltage LVLTBD01 V -
    - - Calibrated fluorescence CPHLPS01 mg m-3 Calibrated against bottle extracted chl-a data
    - - Downwelling PAR irradiance IRRDPP01 µE m-2 s-1 Calculated from PAR meter voltage using manufacturer's coefficients
    - - Potential temperature POTMCV01 °C Computed using UNESCO POTEMP function (using primary T and S)
    - - Sigma-theta SIGTPR01 kg m-3 Computed using UNESCO SVAN function
  • Screening

    The PXF data were compared with the original data files to ensure that no errors had been introduced during the conversion process. The data channels were then screened on a graphics workstation using in-house visualisation software. This allows multiple channels to be viewed simultaneously. The start and end-points of the downcast were marked. The pressure ranges over which bottles were fired were also marked. The bottle firing events were identified by disturbances in CTD parameters on the upcast profiles. All spurious and null data were flagged with appropriate BODC quality control flags.The secondary temperature and salinity channels were used to aid screening of the primary channels only. The primary channels should be used in preference to the secondary channel as they have been quality controlled.

    The following notes were made during the screening of AMT7 CTD data.

    For AMT7027, there was no downcast, so the data from the upcast were screened and processed instead.
    For AMT7023, the tranmissometer, fluorometer and PAR voltage signals were all 0.0, so flagged as suspect.
    For AMT7029-33, the PAR profile was all 0.00, so flagged as suspect.
    For AMT7023, the primary salinity channel was suspect and the whole profile had been flagged. On binning, this channel will result in a null profile, and computed channels such as sigma-theta and potential temperature will also be null. The secondary channel has been quality controlled and should be used in any further work.

  • Loading into the BODC database

    After the data had been screened and quality controlled, the data were loaded into the BODC database under the Oracle RDBMS.

    The data from all 33 casts were loaded into the data tables. However, the PAR profile was deleted from the database for AMT7023 and AMT7029-33, and the PAR, beam attenuation and fluorescence profiles were deleted for AMT7023.


  • Pressure

    The pressure sensor had a mean reading of -0.6 decibar while the CTD was logging in air - this was identified during BODC processing. A pressure correction was, therefore, applied to the data when they were listed from the BODC database.

    PRESPR01(corr) = PRESPR01(raw) + 0.6 decibar (BODC calibration 1597).

  • Temperature

    No reversing thermometer data were available for AMT7, so the CTD sensor data have not been calibrated against another data set. However, the Sea-Bird sensors were tested and calibrated before and after the cruise, and manufacturer's calibrations were applied during Sea-Bird processing. No further correction has been applied to the data at BODC.

  • Salinity

    No bench salinometer data are available for AMT7, so no further calibration of the salinity channel is possible. Users should be aware that the data are uncalibrated and may not be accurate.

  • Fluorometer

    Chlorophyll-a sample data were available from different analysis techniques. At this stage, the CTD fluorometer has been calibrated against fluorometric assays carried out on acetone extracts. This ensures that calibration of all fluorometers, whether CTD or underway, has been carried out using the same technique throughout all AMT cruises to AMT11.

    There were 266 samples which were compared with fluorometer voltage at bottle-firing pressures. Samples were removed from the calibration data set where the standard deviation of the CTD voltage over the bottle firing pressures was <0.01V. Some additional outlying samples were also removed. In general, there was a large degree of scatter in the relationship between fluorometer voltage and chlorophyll-a. The relationship also appeared to vary with time throughout the cruise. It was possible to identify 5 groups of casts for which the relationship was good.


    CPHLPS01 = 9.44 * FVLTWS01 - 0.717 (BODC calibration 2585; r2 = 0.987; N = 7)

    AMT7002 to AMT7007

    CPHLPS01 = 3.83 * FVLTWS01 - 0.156 (BODC calibration 2586; r2 = 0.749; N = 30)

    AMT7008 to AMT7017

    CPHLPS01 = 5.35 * FVLTWS01 - 0.307 (BODC calibration 2587; r2 = 0.702; N = 87)

    AMT7018 to AMT7027

    CPHLPS01 = 5.12 * FVLTWS01 - 0.242 (BODC calibration 2588; r2 = 0.791; N = 73)

    AMT7028 to AMT7033

    CPHLPS01 = 2.71 * FVLTWS01 - 0.0528 (BODC calibration 2589; r2 = 0.840; N = 41)

  • Beam attenuation coefficient

    The Sea-Bird data files contained a transmissometer voltage channel. These data were converted to beam attenuation using the manufacturer's calibration information.

    Beam attenuation = -1 / x * ln ((Vsig - Vd) / (Vref - Vd)),

    where x is the pathlength (0.25m), Vsig is the output voltage, Vd is the blocked path reading (0.059), Vref is the output in clean water (4.678).

    No transmissometer air readings were available from the cruise, so the data have not been corrected for possible source decay during the course of the cruise.

  • Irradiance

    Irradiance = 10 lightmeter voltage * (104 * calibration factor), where the wet calibration factor = 2.53 * 10-4 µEinsteins cm-2sec-1.

Project Information

The Atlantic Meridional Transect (AMT) - Phase 1 (1995-2000)

Who was involved in the project?

The Atlantic Meridional Transect (AMT) programme was designed by and implemented as a collaboration between Plymouth Marine Laboratory (PML) and Southampton Oceanography Centre (SOC). The programme was hosted by Plymouth Marine Laboratory and involved additional researchers from UK and international universities throughout its duration.

What was the project about?

When AMT began in 1995 the programme provided a platform for international scientific collaboration, including the calibration and validation of SeaWiFs measurements and products. The programme provided an exceptional opportunity for nationally and internationally driven collaborative research and provided a platform for excellent multi-disciplinary oceanographic research. As an in situ observation system, the data collected by the AMT consortium informed on changes in biodiversity and function of the Atlantic ecosystem during this period of rapid change to our climate and biosphere.

The scientific aims were to assess:

  • mesoscale to basin scale phytoplankton processes
  • the functional interpretation of bio-optical signatures
  • the seasonal, regional and latitudinal variations in mesozooplankton dynamics

When was the project active?

The first phase of the AMT programme ran from 1995 to 2000 and consisted of a total of 12 cruises. A second phase of funding allowed the project to continue for the period 2002 to 2006 with a further 6 cruises.

Brief summary of the project fieldwork/data

The AMT programme undertook biological, chemical and physical oceanographic research during the annual return passage of the RRS James Clark Ross between the UK and the Falkland Islands or the RRS Discovery between the UK and Cape Town, a distance of up to 13,500 km. This transect crossed a range of ecosystems from sub-polar to tropical and from euphotic shelf seas and upwelling systems to oligotrophic mid-ocean gyres. The transect route was covered north-south in September/October and south-north in April/May of each year.

The measurements of hydrographic and bio-optical properties, plankton community structure and primary production completed on the first 12 transects (1995-2000) represent the most coherent set of repeated biogeochemical observations over ocean basin scales. This unique dataset has led to several important discoveries concerning the identification of oceanic provinces, validation of ocean colour algorithms, distributions of picoplankton, identifying new regional sinks of pCO2 and variability in rates of primary production and respiration.

Who funded the project?

The programme was funded by the Natural Environment Research Council (NERC) and further support was received from the National Aeronautics and Space Administration (NASA) with equipment and funding from the Sea-viewing Wild Field-of-view Sensor (SeaWiFS) project.

Data Activity or Cruise Information


Cruise Name JR19980914 (AMT7, JR34)
Departure Date 1998-09-14
Arrival Date 1998-10-25
Principal Scientist(s)James Aiken (Plymouth Marine Laboratory)
Ship RRS James Clark Ross

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:

Flag Description
Blank Unqualified
< 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.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
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
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
Q value below limit of quantification