Metadata Report for BODC Series Reference Number 1733557


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Sea-Bird SBE 43 Dissolved Oxygen Sensor  dissolved gas sensors
Sea-Bird SBE 911plus CTD  CTD; water temperature sensor; salinity sensor
WETLabs ECO BB(RT)D Scattering Meter  optical backscatter sensors
WETLabs C-Star transmissometer  transmissometers
Biospherical QCD-905L underwater PAR sensor  radiometers
Chelsea Technologies Group Aquatracka III fluorometer  fluorometers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Miss Arwen Bargery
Originating Organization British Oceanographic Data Centre, Liverpool
Processing Status banked
Project(s) -
 

Data Identifiers

Originator's Identifier JR15001_AMT25_CTD_S039
BODC Series Reference 1733557
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2015-10-09 12:58
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars
 

Spatial Co-ordinates

Latitude 8.56750 N ( 8° 34.1' N )
Longitude 21.03700 W ( 21° 2.2' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 3.98 m
Maximum Sensor Depth 501.55 m
Minimum Sensor Height 3388.45 m
Maximum Sensor Height 3886.02 m
Sea Floor Depth 3890.0 m
Sensor Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Chart reference - Depth extracted from available chart
 

Parameters

BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
ATTNDR01 1 per metre Attn_Red_25cm Attenuation (red light wavelength) per unit length of the water body by 25cm path length red light transmissometer
BB117G01 1 per metre per nanometre per steradian AttenBS_532nm_117deg Attenuation due to backscatter (532 nm wavelength at 117 degree incidence) by the water body [particulate >unknown phase] by in-situ optical backscatter measurement
BB117NIR 1 per metre per nanometre per steradian AttenBS_700nm_117deg Attenuation due to backscatter (700 nm wavelength at 117 degree incidence) by the water body [particulate >unknown phase] by in-situ optical backscatter measurement
CPHLPM01 1 Milligrams per cubic metre chl-a_water_ISfluor_manufctrcal_sensor1 Concentration 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 manufacturer's calibration applied
CPHLPS01 1 Milligrams per cubic metre chl-a_water_ISfluor_sampcal Concentration 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
DOXYSC01 1 Micromoles per litre WC_dissO2_calib Concentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor and calibration against sample data
IRRDUV01 1 MicroEinsteins per square metre per second SubsurVPAR Downwelling vector irradiance as photons (PAR wavelengths) in the water body by cosine-collector radiometer
OXYSSC01 1 Percent BK_SBE43 Saturation of oxygen {O2 CAS 7782-44-7} in the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor and calibration against sample data and computation from concentration using Benson and Krause algorithm
POPTDR01 1 Percent Trans_Red_25cm Transmittance (red light wavelength) per 25cm of the water body by 25cm path length red light transmissometer
POTMCV01 1 Degrees Celsius WC_Potemp Potential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR01 1 Decibars Pres_Z Pressure (spatial co-ordinate) exerted by the water body by profiling pressure sensor and corrected to read zero at sea level
PSALST01 1 Dimensionless P_sal_CTD Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
SIGTPR01 1 Kilograms per cubic metre SigTheta Sigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
TEMPST01 1 Degrees Celsius WC_temp_CTD Temperature of the water body by CTD or STD
 

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

James Clark Ross Cruise AMT25 (JR15001) CTD Data Quality Document

Temperature, salinity, potential temperature and sigma-theta: Entrainment features were visible in a number of casts, both in the frame mounted (primary) and vane mounted (secondary channels). These features were apparent throughout the thermocline/pycnocline and continued down to varying depths. The level of entrainment can be indicated by a variation between data points of around 0.2 to 0.3 °C in the temperature, of 0.04-0.05 in the salinity and 0.02 kg m-3in sigma-theta. Overall, the primary temperature, salinity and density channels were deemed to be of better quality and were retained for banking in the NODB, while secondary channels were discarded.

Chlorophyll: In circumstances where data were collected at pressures typically > 150 dbar, negative concentrations were frequently visible. These were flagged as anomalous. These resulted from the chlorophyll calibration being optimised for the euphotic zone, in particular the fluorescence/chlorophyll maximum.

Dissolved oxygen concentration and oxygen saturation: Several deep casts exhibited strong variability in the deeper water around 2000 m depth.

Attenuance and transmissance: Casts 003, 004, 006 and 055 had some values outside the parameter range (0-400 m-1) and (0-100%) which were flagged as anomalous. In some cases, the whole profile was flagged. This may be due to a suspect manufacturer's calibration. Although the values should be teated with caution, the shape of the profiles are still representative of the parameter.

Down and up-welling PAR irradiance: Optics casts were taken pre-dawn and at solar noon. Therefore, for almost half the casts, the PAR values are negligible as they were recorded in the dark.


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

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

Housing Plastic or titanium
Membrane

0.5 mil- fast response, typical for profile applications

1 mil- slower response, typical for moored applications

Depth rating

600 m (plastic) or 7000 m (titanium)

10500 m titanium housing available on request

Measurement range 120% of surface saturation
Initial accuracy 2% of saturation
Typical stability 0.5% per 1000 h

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

RRS James Clark Ross Cruise JR15001 AMT25 CTD Instrumentation

The CTD unit was a Sea-Bird Electronics 911 plus system, consisting of an SBE 11 plus deck unit and a 9 plus underwater unit. The CTD was fitted with an altimeter, a downwelling PAR sensor, transmissometer, backscatter sensor and a fluorometer as auxilliary sensors. All instruments were attached to a 24 position stainless steel Sea-Bird SBE 32 carousel water sampler equipped with 24 Ocean Test Equipment 20L water samplers. The table below lists more detailed information about the various sensors.

Sensor Model Serial Number Calibration Date Comments Casts Used
SeaBird CTD deck unit SBE 11plus V1 11P - SeaBird CTD deck unit 1-81 (excluding 49-54)
SeaBird CTD underwater Unit SBE 9plus 09P - - 1-81 (excluding 49-54)
24-way stainless steel frame - - - - 1-81 (excluding 49-54)
SeaBird Submersible Pump - - - - 1-81 (excluding 49-54)
Digiquartz Pressure sensor Paroscientific 410K-134 Digiquartz temperature compensated pressure 0707 22-Jun-15 Frequency 2 1-81 (excluding 49-54)
Primary Temperature Sensor SBE 03P 2705 10-Jun-15 Frequency 0 3-81 (excluding 49-55)
Primary Temperature Sensor SBE 03P 5766 10-Jun-15 Frequency 0 1, 2 and 55
Secondary Temperature Sensor SBE 03P 5766 18-Mar-15 Frequency 3 3-81 (excluding 49-55)
Secondary Temperature Sensor SBE 03P 2705 18-Mar-15 Frequency 3 1, 2 and 55
Primary Conductivity Sensor SBE 04C 2248 14-Jul-15 Frequency 1 3-81 (excluding 49-55)
Primary Conductivity Sensor SBE 04C 4471 14-Jul-15 Frequency 1 1, 2 and 55
Secondary Conductivity Sensor SBE 04C 4471 12-Mar-15 Frequency 4 3-81 (excluding 49-55)
Secondary Conductivity Sensor SBE 04C 2248 12-Mar-15 Frequency 4 1, 2 and 55
Transmissometer WetLabs C-Star - 0.25 m path red light 1399 30-Jun-15 Voltage 0 1-81 (excluding 49-54)
Fluorometer CTG Aquatracka MKlll 088-249 11-May-15 Voltage 1 1-81 (excluding 49-54)
PAR sensor - downwelling irradiance Biospherical/Licor QCD-905L4S 7275 24-Apr-13 Voltage 2 1-81 (excluding 49-54)
BBRTD Light Scatter Sensor Wetlabs ECO-BB - red light (700 nm wavelength) 849 - Voltage 3 3-81 (excluding 49-55)
Altimeter Tritech PA 200 163162 - Voltage 3 1, 2 and 55
Dissolved Oxygen SBE 43 0676 02-Jun-15 Voltage 4 1-81 (excluding 49-54)
Free channel - - - Voltage 5 1-81 (excluding 49-54)
Altimeter Tritech PA 200 163162 - Voltage 6 3-81 (excluding 49-55)
Free channel - - - Voltage 6 1, 2 and 55
BBRTD Light Scatter Sensor Wetlabs - green light (532 nm wavelength) 949 - Voltage 7 3-81 (excluding 49-55)
Free channel - - - Voltage 7 1, 2 and 55

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:

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 .

Chelsea Technologies Group Aquatracka MKIII fluorometer

The Chelsea Technologies Group Aquatracka MKIII is a logarithmic response fluorometer. Filters are available to enable the instrument to measure chlorophyll, rhodamine, fluorescein and turbidity.

It uses a pulsed (5.5 Hz) xenon light source discharging along two signal paths to eliminate variations in the flashlamp intensity. The reference path measures the intensity of the light source whilst the signal path measures the intensity of the light emitted from the specimen under test. The reference signal and the emitted light signals are then applied to a ratiometric circuit. In this circuit, the ratio of returned signal to reference signal is computed and scaled logarithmically to achieve a wide dynamic range. The logarithmic conversion accuracy is maintained at better than one percent of the reading over the full output range of the instrument.

Two variants of the instrument are available, both manufactured in titanium, capable of operating in depths from shallow water down to 2000 m and 6000 m respectively. The optical characteristics of the instrument in its different detection modes are visible below:

Excitation Chlorophyll a Rhodamine Fluorescein Turbidity
Wavelength (nm) 430 500 485 440 *
Bandwidth (nm) 105 70 22 80 *
Emission Chlorophyll a Rhodamine Fluorescein Turbidity
Wavelength (nm) 685 590 530 440 *
Bandwidth (nm) 30 45 30 80 *

* The wavelengths for the turbidity filters are customer selectable but must be in the range 400 to 700 nm. The same wavelength is used in the excitation path and the emission path.

The instrument measures chlorophyll a, rhodamine and fluorescein with a concentration range of 0.01 µg l -1 to 100 µg l -1 . The concentration range for turbidity is 0.01 to 100 FTU (other wavelengths are available on request).

The instrument accuracy is ± 0.02 µg l -1 (or ± 3% of the reading, whichever is greater) for chlorophyll a, rhodamine and fluorescein. The accuracy for turbidity, over a 0 - 10 FTU range, is ± 0.02 FTU (or ± 3% of the reading, whichever is greater).

Further details are available from the Aquatracka MKIII specification sheet .

Biospherical Instruments Log Quantum Cosine Irradiance Sensor QCD-905L

The QCD-905L is a submersible radiometer designed to measure irradiance over Photosynthetically Active Radiation (PAR) wavelengths (400-700 nm). It features a cosine directional response when fully immersed in water.

The sensor is a blue-enhanced high stability silicon photovoltaic detector with dielectric and absorbing glass filter assembly, and produces a logarithmic output. Normal output range is -1 to 6 volts with 1 volt per decade. Typically, the instrument outputs 5 volts for full sunlight and has a minimum output of 0.001% full sunlight, where typical noon solar irradiance is 1.5 to 2 x 10 17 quanta cm -2 s -1 . The instrument can be calibrated with constants for µE cm -2 s -1 or quanta cm -2 s -1 .

The QCD-905L can be coupled to a fixed range data acquisition system like a CTD (Conductivity-Temperature-Depth) profiler or current meter. It has an aluminium and PET housing, and a depth rating of 7000 m.

Specifications

Wavelength 400 to 700 nm
Output range -1 to 6 V, with 1 V decade -1
Operating temperature -2 to 35°C
Depth range 0 - 7000 m

Further details can be found in the manufacturer's manual .

WETLabs Single-angle Backscattering Meter ECO BB

An optical scattering sensor that measures scattering at 117°. This angle was determined as a minimum convergence point for variations in the volume scattering function induced by suspended materials and water. The measured signal is less determined by the type and size of the materials in the water and is more directly correlated to their concentration.

Several versions are available, with minor differences in their specifications:

Specifications

Wavelength 471, 532, 660 nm
Sensitivity (m -1 sr -1 )

1.2 x 10 -5 at 470 nm

7.7 x 10 -6 at 532 nm

3.8 x 10 -6 at 660 nm

Typical range ~0.0024 to 5 m -1
Linearity 99% R 2
Sample rate up to 8Hz
Temperature range 0 to 30°C
Depth rating

600 m (standard)

6000 m (deep)

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.

Specifications

Pathlength 10 or 25 cm
Wavelength 370, 470, 530 or 660 nm
Bandwidth

~ 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 .

RRS James Clark Ross Cruise JR15001 AMT25 CTD Processing Document

Sampling Protocol for Data Acquisition and Analysis

A total of 74 CTD casts (casts 001 to 081 but excluding casts 049 to 054) were completed during the AMT25 cruise. The cruise departed from Immingham, UK on 15th September 2016 and arrived in Port Stanley, Falkland Islands on 04th November 2016. The ship docked at Portsmouth to take on fuel at approximately 07:00 on 17th September 2015 and then departed Portsmouth on 17th September 2015 at 16:00. The ship briefly stopped at the Azores on 24th September 2015 (did not dock) to exchange personnel and made a port call at Praia, Cape Verde on 07th October 2015 for several hours, departing the same day. A change of personnel from AMT to BAS scientists occurred at Ascension Island on 15th to 18th October 2015. CTD data collected during the phase around Ascension Island are available as part of a BAS funded project and consisted of CTD's 049 to 054. All casts were conventional stainless steel profiling casts with water sampling by 24 x 20L OTE Niskin bottles. Casts were carried out at around 04:00-05:00 and around 13:00-14:00 ship time each day weather permitting.

BODC Cruise Processing

CTD casts were recorded using the Sea-Bird data collection software Seasave-Win32. The software outputs were then processed following the BODC recommended guidelines using SBE Data Processing-Win32 v7.23.2; the processing routines are named after each stage in brackets < >. The software applied the calibrations as appropriate through the instrument configuration file to the data in engineering units output by the CTD hardware.

An ASCII file (CNV) containing the 24 Hz data for up and down casts was generated from the binary Sea-Bird files for each cast <DatCnv>. Files were created for each cast containing the mean values of all the variables at the bottle firing events <Bottle Summary>. Using the CNV files processing routines were applied to remove pressure spikes <WildEdit>, the oxygen sensor was then shifted relative to the pressure by 2 seconds, to compensate for the lag in the sensor response time <AlignCTD> and the effect of thermal 'inertia' on the conductivity cells was removed <CellTM>. The surface soak was identified for each cast, removed and LoopEdit run. Salinity and oxygen concentration were re-derived and density (sigma-theta) values were derived <Derive> after the corrections for sensor lag and thermal 'inertia' had been applied. The CTD files produced from Sea-Bird processing were converted from 24 Hz ASCII files into 1 dbar downcast files for calibration and visualisation onboard <BinAverage>. The initial salinity and oxygen channels produced at the DatCnv stage, along with the conductivity, voltage and altimeter channels were removed from the 1 dbar downcast files <Strip>.

The sensor values at bottle firing produced by the Bottle Summary routine were collated and used to generate calibrations for the salinity, oxygen and fluorometer channels where appropriate. Water samples were collected from each cast for measurement of salinity (bench salinometer) and chlorophyll-a (filtration, acetone extraction and fluorometer measurement) and from the pre-dawn cast each day for oxygen (Winkler titration).

The table below shows the parameters available in the final processed CNV files provided to BODC and the channel names in the final ODV file. Calibrated salinity, oxygen and fluorometer channels were then added to the profiles where appropraite using calibration equations derived from the bottle file data compared against discrete samples collected from the CTD water bottles on each cast.

Parameter Name in Sea-Bird CNV Units Parameter Name in ODV file Units Comments
prDM: Pressure, Digiquartz db Pressure dbar -
t090C: Temperature ITS-90, deg C Temperature_1 deg C -
t190C: Temperature, 2 ITS-90, deg C Temperature_2 deg C -
sal00: Salinity, Practical PSU Salinity1_SBEcal   -
sal11: Salinity, Practical 2 PSU Salinity2_SBEcal   -
sbeox0Mm/L: Oxygen, SBE 43 µmol/l Oxy_conc_SBEcal µmol/l -
CStarTr0: Beam Transmission, WET Labs C-Star % Beam transmission % -
CStarAt0: Beam Attenuation, WET Labs C-Star 1/m Beam attenuance 1/m -
flC: Fluorescence, Chelsea Aqua 3 Chl Con µg/l Fluorometer_notional_calibration mg m -3 -
par: PAR/Irradiance, Biospherical/Licor   PAR_down µE m -2 s -1 -
turbWETbb0: Turbidity, WET Labs ECO BB m^-1/sr Backscatter_1 m^-1/sr -
turbWETbb1: Turbidity, WET Labs ECO BB 2 m^-1/sr Backscatter_2 m^-1/sr -
- - chl_cal µg/l Channel derived from calibrating fluorescence channel with sample data.
- - Oxy cal µmol/l Channel derived from calibrating oxygen channel with sample data.

Calibrations

The method used for calibration was to generate an offset between the discrete water sample measurement (salinity/oxygen/chl-a) and the nominal value from the sensor at bottle firing. The offsets were then plotted against the discrete sample values and a linear regression applied.

Offset = a * Discrete sample + b

Where offset = Discrete sample - Sensor value

To give Calibrated value = 1/(1-a) * Sensor value + b/(1-a)

Where the regression was not significant the mean value of the offset was applied if appropriate. All calibration datasets are available upon request from BODC post cruise.

Temperature

There were no independent measurements of temperature made during the cruise and the sensors on the rig returned consistent data. No further calibration of these sensors has been carried out.

Salinity

The salinity channels were calibrated against bench salinometer measurements from 2 - 4 samples collected from each cast. Further details of these measurements can be found in the documentation for the discrete salinity dataset.

The regression for both salinity sensors was not significant and so was not applied. The mean offset for both sensors was also not applied as the standard deviation of the offsets was larger than the average offset.

Primary Conductivity Sensor SBE 4C-2248: n = 106; r 2 = 0.011; p = 0.2885; mean offset = 0.0010; standard deviation of offsets = 0.0130

Secondary Conductivity Sensor SBE 4C-4471: n = 107; r 2 = 0.0011; p = 0.7367; mean offset=0.0064; standard deviation of offsets = 0.0148

Oxygen

The oxygen sensor was calibrated against discrete oxygen sample Winkler titration measurements from up to 18 samples collected from the pre-dawn and solar noon CTD's.

The oxygen sensor operated without problem throughout the cruise

Several Winkler titration samples did not fit the pattern observed with the data from the other casts and were excluded from the calibration dataset.

The calibration equation was:

Calibrated O 2 (in µmol/l) = 1.0526 * sensor O 2 (in µmol/l) + 12.9936 (n=664; r 2 =0.137; p < 0.001);

Fluorescence

The CTD deployed Chelsea AQUAtracka MkIII fluorometer was calibrated against extracted chlorophyll-a measurements made on seawater collected by Niskin bottles on each cast. Calibrations were derived individually for each cast where appropriate as shown in the table below. Samples of seawater from CTD niskin bottles were collected to calibrate the CTD fluorometer with the analytical method following Welschmeyer (1994). Samples were collected at 74 stations from up to 10 depths including light depths from 97, 55, 33, 14, 7, 1 and 0.1%. Each sample of 250 ml was filtered through 47 mm 0.2 µm polycarbonate filters. The filters were then placed in a vial with 10 ml 90% acetone and left in a freezer for 24 hours. The samples were then analysed on a pre-calibrated Turner Designs Trilogy fluorometer with a non-acidified chl module (CHL NA #046) fitted. The pre-calibrated fluorometer produced anomalous results during analysis throughout the cruise, however as there were no dilutions of pure chlorophyll stock available, the calibration was not checked or modified. To compensate for this, the fluorometer was back-calibrated at PML after the cruise and the results were updated based on the new fluorometer calibration. The regression analysis was not significant for casts 3, 4, 5, 44, 46, 76 and 78 and so the fluorometer channel on these casts were not calibrated.

The Chelsea AQUAtracka MkIII fluorometer attached to the CTD rig operated without problem.

References

Welschmeyer N.A., 1994. Fluorometric analysis of chlorophyll-a in the presence of chlorophyll-b and phaeopigments. Limnology and Oceanography, 39(8), 1985-1992.

CTD Calibration Equation N R 2
CTD001 and CTD002 combined CPHLPS01 = 1.445 * CPHLPM01 - 0.041 10 0.9805
CTD006 CPHLPS01 = 1.467 * CPHLPM01 - 0.038 6 0.9195
CTD007 CPHLPS01 = 1.631 * CPHLPM01 - 0.023 5 0.9743
CTD008 CPHLPS01 = 1.558 * CPHLPM01 - 0.053 7 0.704
CTD009 CPHLPS01 = 2.255 * CPHLPM01 - 0.057 5 0.9878
CTD010 CPHLPS01 = 3.005 * CPHLPM01 - 0.072 7 0.8546
CTD011 CPHLPS01 = 2.111 * CPHLPM01 - 0.033 7 0.9809
CTD012 and CTD013 combined CPHLPS01 = 1.602 * CPHLPM01 - 0.001 13 0.9064
CTD014 CPHLPS01 = 2.137 * CPHLPM01 - 0.024 8 0.9564
CTD015 CPHLPS01 = 1.433 * CPHLPM01 - 0.013 6 0.8743
CTD016 CPHLPS01 = 2.888 * CPHLPM01 - 0.055 15 0.9597
CTD017 CPHLPS01 = 2.482 * CPHLPM01 - 0.007 7 0.9798
CTD018 CPHLPS01 = 2.991 * CPHLPM01 - 0.039 7 0.9968
CTD019 CPHLPS01 = 2.227 * CPHLPM01 -0.047 7 0.9756
CTD020 CPHLPS01 = 3.509 * CPHLPM01 - 0.05 8 0.9978
CTD021 CPHLPS01 = 2.573 * CPHLPM01 - 0.043 7 0.9653
CTD022 CPHLPS01 = 2.946 * CPHLPM01 -0.051 7 0.9196
CTD023 CPHLPS01 = 2.021 * CPHLPM01 -0.028 8 0.8957
CTD024 CPHLPS01 = 2.487 * CPHLPM01 - 0.024 9 0.9921
CTD025 CPHLPS01 = 2.326 * CPHLPM01 -0.017 9 0.9646
CTD026 CPHLPS01 = 1.646 * CPHLPM01 - 0.016 9 0.7377
CTD027 CPHLPS01 = 2.724 * CPHLPM01 - 0.031 8 0.9852
CTD028 CPHLPS01 = 2.139 * CPHLPM01 - 0.016 7 0.9235
CTD029 CPHLPS01 = 1.494 * CPHLPM01 + 0.01 7 0.7704
CTD030 CPHLPS01 = 2.363 * CPHLPM01 - 0.012 8 0.9488
CTD031 CPHLPS01 = 1.507 * CPHLPM01 + 0.004 6 0.8318
CTD032 CPHLPS01 = 2.822 * CPHLPM01 - 0.084 6 0.9778
CTD033 CPHLPS01 = 4.177 * CPHLPM01 -0.127 6 0.9356
CTD034 CPHLPS01 = 2.693 * CPHLPM01 -0.041 6 0.9119
CTD035 CPHLPS01 = 2.389 * CPHLPM01 - 0.014 6 0.7956
CTD036 CPHLPS01 = 4.019 * CPHLPM01 - 0.097 5 0.9663
CTD037 CPHLPS01 = 2.471 * CPHLPM01 - 0.094 8 0.8408
CTD038 CPHLPS01 = 3.409 * CPHLPM01 - 0.158 6 0.9762
CTD039 CPHLPS01 = 3.17 * CPHLPM01 - 0.056 4 0.9922
CTD040 CPHLPS01 = 2.251 * CPHLPM01 - 0.032 7 0.9051
CTD041 CPHLPS01 = 1.377 * CPHLPM01 + 0.009 6 0.8528
CTD042 CPHLPS01 = 1.296 * CPHLPM01 + 0.011 7 0.7323
CTD043 CPHLPS01 = 1.355 * CPHLPM01 + 0.004 6 0.7833
CTD045 CPHLPS01 = 1.311 * CPHLPM01 - 0.026 5 0.9093
CTD047 CPHLPS01 = 1.54 * CPHLPM01 - 0.006 9 0.7587
CTD048 CPHLPS01 = 1.885 * CPHLPM01 - 0.05 6 0.9117
CTD055 CPHLPS01 = 1.388 * CPHLPM01 + 0.036 6 0.5822
CTD056 CPHLPS01 = 1.635 * CPHLPM01 + 0.009 7 0.9126
CTD057 CPHLPS01 = 1.55 * CPHLPM01 + 0.019 9 0.7591
CTD058 CPHLPS01 = 1.383 * CPHLPM01 + 0.026 9 0.6382
CTD059 CPHLPS01 = 1.598 * CPHLPM01 + 0.002 9 0.606
CTD060 CPHLPS01 = 1.335 * CPHLPM01 - 0.001 9 0.5157
CTD061 CPHLPS01 = 2.043 * CPHLPM01 + 0.003 10 0.9579
CTD062 CPHLPS01 = 2.222 * CPHLPM01 - 0.007 10 0.9763
CTD063 CPHLPS01 = 1.538 * CPHLPM01 + 0.021 7 0.8761
CTD064 CPHLPS01 = 1.704 * CPHLPM01 - 0.012 8 0.9411
CTD065 CPHLPS01 = 2.92 * CPHLPM01 - 0.032 9 0.9821
CTD066 CPHLPS01 = 2.12 * CPHLPM01 - 0.007 9 0.9755
CTD067 CPHLPS01 = 1.98 * CPHLPM01 - 0.004 10 0.8756
CTD069 CPHLPS01 = 3.028 * CPHLPM01 - 0.027 10 0.9593
CTD070 CPHLPS01 = 2.279 * CPHLPM01 - 0.032 10 0.9574
CTD071 CPHLPS01 = 1.951 * CPHLPM01 - 0.046 8 0.6748
CTD072 CPHLPS01 = 1.517 * CPHLPM01 - 0.041 9 0.8198
CTD073 CPHLPS01 = 1.495 * CPHLPM01 - 0.01 7 0.8266
CTD074 CPHLPS01 = 1.328 * CPHLPM01 - 0.008 8 0.6515
CTD075 CPHLPS01 = 1.798 * CPHLPM01 + 0.018 8 0.8828
CTD077 CPHLPS01 = 1.423 * CPHLPM01 + 0.002 7 0.4383
CTD079 CPHLPS01 = 1.158 * CPHLPM01 + 0.03 8 0.3328
CTD080 CPHLPS01 = 1.394 * CPHLPM01 + 0.021 10 0.844
CTD081 CPHLPS01 = 1.499 * CPHLPM01 - 0.007 7 0.6712

BODC post-processing and screening

Reformatting

The data were converted from tab delimited ODV format into BODC internal format using BODC transfer function 480. Final calibrated channels have been transferred were possible, but where a calibration was not possible, the uncalibrated channel has been transferred. The following table shows how each variable was mapped to appropriate BODC parameter codes. Oxygen saturation, sigma-theta and potential temperature were derived and added to the profiles during the transfer process.

Originator's Parameter Name Units Description BODC Parameter Code Units Comments
Pressure dbar Pressure (spatial co-ordinate) exerted by the water body by profiling pressure sensor and corrected to read zero at sea level PRESPR01 dbar -
Temperature_1 deg C Temperature of the water body by CTD or STD TEMPST01 Degrees Celsius -
Temperature_2 deg C Temperature of the water body by CTD or STD TEMPST02 Degrees Celsius Secondary channel removed after transfer
Beam transmission % Transmittance (red light wavelength) per 25cm of the water body by 25cm path length red light transmissometer. POPTDR01 percent -
Beam attenuance 1/m Attenuance (red light wavelength) per unit length of the water body by 25cm path length red light transmissometer ATTNDR01 per metre -
Fluorometer_notional_calibration mg m -3 Concentration 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 manufacturer's calibration applied CPHLPM01 Milligrams per cubic metre Channel present only in casts 3, 4, 5, 44, 46, 76 and 78 which were not calibrated for chlorophyll
Chl_cal mg m -3 Concentration 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 CPHLPS01 Milligrams per cubic metre Individual calibrations for each cast. Channel applied to all casts except 3, 4, 5, 44, 46, 76 and 78
PAR_down MicroEinsteins per square metre per second Downwelling vector irradiance as photons (PAR wavelengths) in the water body by cosine-collector radiometer IRRDUV01 MicroEinsteins per square metre per second -
Backscatter_1 m -1 /sr Attenuation due to backscatter (700 nm wavelength at 117 degree incidence) by the water body [particulate >unknown phase] by in-situ optical backscatter measurement BB117NIR per metre per nanometre per steradian Channel not present on casts 1, 2 and 55
Backscatter_2 m -1 /sr Attenuance due to backscatter (532 nm wavelength at 117 degree incidence) by the water body [particulate >unknown phase] by in-situ optical backscatter measurement BB117G01 per metre per nanometre per steradian Channel not present on casts 1, 2 and 55
Salinity1_SBEcal Dimensionless Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm PSALST01 Dimensionless -
Salinity2_SBEcal Dimensionless Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm PSALST02 Dimensionless Secondary channel removed after transfer
Oxy_cal µmol/l Concentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor and calibration against sample data DOXYSC01 Micromoles per litre Calibration against sample data applied to all casts
Oxy_conc_SBEcal µmol/l Concentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor and no calibration against sample data DOXYSU01 Micromoles per litre Uncalibrated channel not transferred
- - Potential temperature of the water body by computation using UNESCO 1983 algorithm POTMCV01 Degrees Celsius Generated during transfer
- - Potential temperature of the water body by second sensor and computation using UNESCO 1983 algorithm POTMCV02 Degrees Celsius Generated during transfer, then dropped
- - Sigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm SIGTPR01 Kilograms per cubic metre Generated during transfer
- - Sigma-theta of the water body by second CTD sensors and computation from salinity and potential temperature using UNESCO algorithm SIGTPR02 Kilograms per cubic metre Generated during transfer, then dropped
- - Saturation of oxygen {O2 CAS 7782-44-7} in the water body [dissolved plus reactive particulate phase] by Sea-Bird SBE 43 sensor and calibration against sample data and computation from concentration using Benson and Krause algorithm OXYSSC01 Percent Generated during transfer

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. Limnology and Oceanography, 29(3), pp. 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, pp. 53

Screening

Reformatted CTD data were transferred onto a graphics work station for visualisation using the in-house editor EDSERPLO. No data values were edited or deleted. Flagging was achieved by modification of the associated BODC quality control flag for suspect or null values.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name JR15001 (AMT25, JR864)
Departure Date 2015-09-15
Arrival Date 2015-11-04
Principal Scientist(s)David Barnes (British Antarctic Survey), Jonathan Sharples (University of Liverpool Department of Earth, Ocean and Ecological Sciences), Tim Smyth (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