Metadata Report for BODC Series Reference Number 1046566


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Sea-Bird SBE 43 Dissolved Oxygen Sensor  dissolved gas sensors
Chelsea Technologies Group Aquatracka fluorometer  fluorometers
Sea-Bird SBE 911plus CTD  CTD; water temperature sensor; salinity sensor
Benthos PSA-916T Sonar Altimeter  altimeters
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Mr Hugh Venables
Originating Organization British Antarctic Survey
Processing Status banked
Project(s) ANDREX
 

Data Identifiers

Originator's Identifier CTD_JR239_067_2DB_CAL
BODC Series Reference 1046566
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-04-11 07:04
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 61.83250 S ( 61° 50.0' S )
Longitude 19.79710 W ( 19° 47.8' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 6.93 m
Maximum Sensor Depth 4454.0 m
Minimum Sensor Height 46.0 m
Maximum Sensor Height 4493.07 m
Sea Floor Depth 4500.0 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 Unspecified -
 

Parameters

BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
AHSFZZ01 1 Metres Height Height above bed in the water body
CNCLCCI1 1 Siemens per metre Cond_ind_cal Electrical conductivity of the water body by in-situ conductivity cell and calibration against independent measurements
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
DOXYCZ01 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 in-situ sensor and calibration against sample data
OXYSZZ01 1 Percent O2Sat Saturation of oxygen {O2 CAS 7782-44-7} in the water body [dissolved plus reactive particulate phase]
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
PSALCU01 1 Dimensionless P_sal_CTD_uncalib Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm and NO calibration against independent measurements
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
TEMPCC01 1 Degrees Celsius Cal_CTD_Temp Temperature of the water body by CTD and verification against independent measurements
TOKGPR01 1 Litres per kilogram Vol2MassCTD Conversion factor (volume to mass) for the water body by CTD and computation of density (in-situ potential temperature surface pressure) reciprocal from pressure, temperature and salinity
 

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


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 .

Benthos Programmable Sonar Altimeter (PSA) 916 and 916T

The PSA 916 is a submersible altimeter that uses the travel time of an acoustic signal to determine the distance of the instrument from a target surface. It provides the user with high resolution altitude or range data while simultaneously outputting data through a digital serial port. A wide beam angle provides for reliable and accurate range measurements under the most severe operational conditions. The instrument is electronically isolated to eliminate any potential signal interference with host instrument sensors. The PSA 916 is an upgrade of the PSA 900.

The standard model (PSA 916) has an operational depth range of 0 - 6000 m, while the titanium PSA 916T has a depth range of 0 - 10000 m. All other specifications for the two versions are the same.

Specifications

Transmit frequency 200 kHz
Transmit pulse width 250 µs
Beam pattern 14° conical
Pulse repetition rate

internal selection: 5 pps

external selection: up to 5 pps- user controlled

Range

100 m full scale

1.0 m guaranteed minimum

0.8 m typical

Range

1 cm for RS232 output

2.5 cm for analog output

Operating depth 6000 m (PSA 916) or 10000 m (PSA 916T)

Further details can be found in the manufacturer's specification sheets for the PSA 916 and the PSA 916T .

Instrument Description

CTD Unit and Auxiliary Sensors

Sensor Model Serial Number Calibration (UT) Comments
CTD underwater unit Sea-Bird 9 plus underwater unit 09P-0869 - -
CTD deck unit Sea-Bird 11 plus underwater unit 11P-0502 - -
24-position carousel Sonardyne 24-position carousel 234002-001 - -
Pressure transducer Paroscientific Digiquartz 42K-101 46253 31/07/2009 -
Conductivity sensor 1 SBE 4 04C-2450 10/02/2010 -
Conductivity sensor 2 SBE 4 04C-2571 29/01/2010 -
Temperature sensor 1 SBE 3 plus 03P-2919 13/02/2010 -
Temperature sensor 2 SBE 3 plus 03P-4782 12/02/2010 -
Dissolved oxygen SBE 43 43-0619 27/10/2009 Oxygen sensor changed to S/N 43-0242 after cast 68
Transmissometer Chelsea Alphatracka MKII 0971007-001 2010-03-22 -
Fluorometer Chelsea Aquatracka MKIII 088195 2008-05-27 -
Altimeter Benthos PSA-916T 7Hz 874 - -
Light scattering sensor WetLabs Light scattering sensor BBRTD-168 - -
Thermometer SeaBird SBE35 Deep Ocean Standards Thermometer 0005 - -
LADCP RDI WorkHorse Monitor 13191 - Downward-looking, LADCP changed to S/N 12369 after cast 20
24x 20 litre water samplers Ocean Test Equipment ES-20L water samplers 01-24 - -

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 .

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

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

BODC Processing

The data were received in one netcdf file per station and contained data from primary and secondary sensors, with various filtered versions. Most of the uncalibrated filtered data (excluding fluor_filt) were not loaded as they had been superseded by calibrated data. The transmittance and optical backscatter channels were not loaded as these were problematic (see cruise report p.17). The originator derived channels were also not loaded, with potential temperature and sigma-theta re-derived by BODC. In addition, press_filt was not required as press_filt_bin_average was a more appropriate pressure variable to use. The remaining data channels were converted into the internal BODC format.

The reformatted data were visualised using the in-house EDSERPLO software. The data were screened and quality control flags were applied to data as necessary. The conductivity primary sensor 1 was found to have malfunctioned for three of the casts, 27, 38 and 39. This lead to pronounced salinity and density inversions of >0.5 in these profiles. The conductivity from the secondary sensor 2 appeared to be unaffected, whilst sensor 1 and sensor 2 data compared well for the other casts. Therefore, for casts 27, 38 and 39 only sensor 2 data (all variables) have been included and all BODC derived channels have been calculated using sensor 2 data only. The remaining 92 casts have data from the primary sensors only and all derived channels have been calculated from these.

The following table shows how the variables within the netCDF files were mapped to appropriate BODC parameter codes:

Originator's Parameter Name Units Description BODC Parameter Code Units Comments
pad_variable - Empty - - Not loaded.
press_filt_bin_average dbar Average pressure (rather than bin midpoint). PRESPR01 dbar -
press_filt dbar Pressure exerted by the water column (bin midpoint). - - Not loaded.
pressure_temp °C Internal temperature measured from CTD pressure sensor. - - Not loaded.
scan number CTD record number. - - Not loaded.
flag number Flag channel. - - Not loaded as originator did not use.
time seconds Time from switching on CTD. - - Not loaded, time taken from header.
cond1_filt mS cm -1 Conductivity from sensor 1, processed, cleaned but uncalibrated. - - Not loaded.
cond2_filt mS cm -1 Conductivity from sensor 2, processed, cleaned but uncalibrated. - - Not loaded.
temp1_filt °C Temperature from sensor 1, processed, cleaned but uncalibrated. - - Not loaded.
temp2_filt °C Temperature from sensor 2, processed, cleaned but uncalibrated. - - Not loaded.
oxygen_filt µmol kg -1 Dissolved oxygen concentration, processed, cleaned but uncalibrated. - - Not loaded.
altimeter m Height above bed from CTD, no processing. AHSFZZ01 m -
fluor_filt µg l -1 Concentration of chlorophyll from CTD, no processing or samples available for calibration. CPHLPM01 mg m -3 -
transmittance_filt Percent Transmittance, processed, cleaned but uncalibrated. - - Not loaded.
backscatter_filt - Optical backscatter. - - Not loaded.
temp1_cal °C Temperature from sensor 1, processed, cleaned and calibrated from SBE35 data. TEMPCC01 °C All casts except for 27, 38 and 39. Calibrated against reference thermometer SeaBird SBE35.
temp2_cal °C Temperature from sensor 2, processed, cleaned and calibrated from SBE35 data. TEMPCC02 °C For casts 27, 38 and 39 only. Calibrated against reference thermometer SeaBird SBE35.
cond1_cal mS cm -1 Conductivity from sensor 1, processed, cleaned and calibrated from bottle samples. CNCLCCI1 S m -1 All casts except for 27, 38 and 39. Converted to siemens per metre by dividing the original by 10.
cond2_cal mS cm -1 Conductivity from sensor 2, processed, cleaned and calibrated from bottle samples. CNCLCCI2 S m -1 For casts 27, 38 and 39 only. Converted to siemens per metre by dividing the original by 10.
oxygen_cal µmol kg -1 Dissolved oxygen concentration, processed, cleaned and calibrated from bottle samples. DOXYCZ01 µmol l -1 Converted to micromoles per litre by multiplying the original value by 44.66.
depth m - - - Not loaded.
psal_cal pss-78 Practical salinity calculated from calibrated conductivity and temperature data from sensors 1, using the equation of state from UNESCO (1978). PSALCU01 Dimensionless All casts except for 27, 38 and 39.
psal2_cal pss-78 Practical salinity calculated from calibrated conductivity and temperature data from sensors 2, using the equation of state from UNESCO (1978). PSALCU02 Dimensionless For casts 27, 38 and 39 only.
potemp_cal °C Potential temperature calculated from calibrated data from primary sensors. - - Not loaded.
potemp2_cal °C Potential temperature calculated from calibrated data from secondary sensors. - - Not loaded.
sigma0_cal kg m -3 Potential density computed at the surface. - - Not loaded.
sigma2_cal kg m -3 Potential density computed at 2000 dbar. - - Not loaded.
sigma4_cal kg m -3 Potential density computed at 4000 dbar. - - Not loaded.
- - Sigma-theta. SIGTPR01 kg m -3 Generated by BODC using the Fofonoff and Millard (1983) algorithm.
- - Potential temperature. POTMCV01 °C Generated by BODC using the Fofonoff and Millard (1983) algorithm.
- - Oxygen saturation. OXYSZZ01 Percent Generated by BODC using the Benson and Krause (1984) algorithm.

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, No.29(3), 620-632pp.

Fofonoff, N.P. and Millard, R.C., 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science, No.44, 53pp.

UNESCO, 1978. Eighth report of the joint panel on oceanographic tables and standards. UNESCO Technical Papers in Marine Science, No.28, 35pp.

Originator's Data Processing

Sampling Strategy

Ninety six CTD profiles were performed during the cruise, 95 were received (cast 5 abandoned as pumped blocked, cast 6 at same location). CTD casts are labelled from 1 to 98. Cast 1 is a test cast, and casts 69, 76 and 81 were cancelled due to time constraints. Data were measured at 24 Hz and averaged to 2 dbar.

Further details of sampling problems and sensor failures can be found in the cruise report.

Field Calibrations

Bottle samples were drawn for salinity and oxygen from each available bottle depth for every CTD cast. Some bottles were leaking badly and were excluded from any sampling. The bottle depths were chosen from the depths: surface, 25, 50, 75, 100, 150, 200, 300, 400, 600, 800, 1000, (1250), 1500, (1750), 2000, (2250), 2500, (2750), 3000, (3250), 3500, (3750), 4000, (4250), 4500, (4750), 5000, bottom-200, bottom-150, bottom-100, bottom-50, bottom with depths in brackets being dropped (shallowest first) where necessary. On some casts some bottles (especially bottle 20) were double fired, at the expense of another depth, as they were deemed likely to leak. On some casts the bottle depths differed from this scheme due to errors; either deeper depths were dropped in favour of shallower or due to transcription errors.

The following processing steps were taken:
1) Temperature 1 and temperature 2 calibrated from SBE35 thermometer (see section 3c).
2) Bottle conductivity 1 and conductivity 2 back calculated
3) Conductivity calibrations found and applied
4) Salinity recalculated
5) Salinity checked
6) Oxygen calibrated

Conductivity

Conductivity was calibrated rather than salinity using bottle samples from the CTD rosette compared to CTD conductivity. Overall sensor performance was assessed to be good. Bottle sample salinity and CTD salinity were also compared to demonstrate behaviour of sensors. It was concluded that CTD salinity 1 did not have an offset, although temperature 1 did, and so conductivity 1 was calibrated. Salinity 2 had a slight pressure-dependent offset and was therefore calibrated.

The following method provided by Brian King is the standard National Oceanography Centre Southampton scientists' approach for calibrating conductivity;
1) Bottle salinity, as measured by the bench salinometer, is converted to 'potential conductivity' at the CTD bottle location using in situ temperature and pressure, and the CSIRO EOS-80 Seawater algorithms.
2) CTD conductivity is calibrated against this 'potential conductivity'.
3) CTD salinity is derived using the corrected conductivity data and the PSS-78 algorithm.

Temperature

Temperature data were calibrated using independent temperature values from SBE35 thermometer compared to CTD temperature. Both primary and secondary sensors were calibrated independently.

Oxygen

Oxygen data were calibrated against dissolved oxygen measurements taken from discrete bottles and determined using the Winkler method on board the ship. The CTD oxygen sensor behaviour was observed to have jumped between casts 23 and 26. The sensor was changed after cast 68. See cruise report for further calibration details.


Project Information

Antarctic Deep Water Rates of Export (ANDREX) project document

ANDREX is a UK field programme aimed at investigating the role of the Weddell Gyre in the Meridional Overturning Circulation (MOC) and its influence on deep ocean properties.

The MOC is a critical regulator of Earth's climate and is crucial for deep water ventilation across the globe. Surface currents transport waters towards the poles, where they become dense and sink, flowing equatorward as deep, cool currents. The MOC ensures that the deep oceans remain ventilated and conducive to life, and is also important for anthropogenic carbon sequestration. The southern closure of the MOC in the Weddell Sea is strongly influenced by the Weddell Gyre, which facilitates the exchange of waters between the Antarctic Circumpolar Current (ACC) and the waters of the continental shelf. Cooling and sea ice formation in the Weddell Sea lead to overturning of the water column and the ventilation of Antarctic Bottom Water (AABW), which flows out of the Weddell Sea and into the deep oceans to the north. Thus, the Weddell Gyre plays an important role in the properties of deep ocean waters on a global scale.

The goals of ANDREX are to investigate the exchange of water masses between the ACC and the Weddell Sea, including AABW formation and ventilation rates, carbon and nutrient cycling, the influence of fresh water input from sea ice, precipitation and glacial melt, and the role of the Weddell Gyre in anthropogenic carbon sequestration. The project includes hydrographic, ventilation tracer, biogeochemical and bathymetric measurements along the outer rim of the Weddell Gyre.

ANDREX is funded by the UK Natural Environment Research Council (NERC) Antarctic Funding Initiative (AFI) and involves scientists from the National Oceanography Centre, Southampton (NOC), the British Antarctic Survey (BAS), the University of East Anglia (UEA), the University of Manchester, the Alfred Wegener Institut (AWI) and the Woods Hole Oceanographic Institution (WHOI).

For more information please see the official project website at ANDREX


Data Activity or Cruise Information

Cruise

Cruise Name JR20100319 (JR235, JR236, JR239)
Departure Date 2010-03-19
Arrival Date 2010-04-24
Principal Scientist(s)Mike Meredith (British Antarctic Survey)
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