Metadata Report for BODC Series Reference Number 1643089


Metadata Summary

Data Description

Data Category Towed STD/CTD
Instrument Type
NameCategories
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 towed unmanned submersible
Originating Country United Kingdom
Originator Dr Alberto Naveira Garabato
Originating Organization University of Southampton School of Ocean and Earth Science
Processing Status banked
Project(s) DIMES
 

Data Identifiers

Originator's Identifier JC041_TOWYO9_14
BODC Series Reference 1643089
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2009-12-13 05:46
End Time (yyyy-mm-dd hh:mm) 2009-12-13 06:02
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 58.02461 S ( 58° 1.5' S )
Longitude 53.66847 W ( 53° 40.1' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 16.84 m
Maximum Sensor Depth 495.76 m
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
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 Approximate - Depth is only approximate
Sea Floor Depth Datum -
 

Parameters

BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
CNDCST01 1 Siemens per metre CTDCond Electrical conductivity of the water body by CTD
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
PSALCC01 1 Dimensionless P_sal_CTD_calib Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm and 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
TEMPS901 1 Degrees Celsius CTDTmp90 Temperature (ITS-90) 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


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

Instrument Descriptions

CTD Unit and Auxiliary Sensors

Sensor Model Serial Number Calibration (UT) Comments
CTD underwater unit Sea-Bird 9plus underwater unit 09P-19817-0528 - -
Submersible pump Sea-Bird 5T submersible pump 05T-3609 - -
Secondary submersible pump Sea-Bird 5T submersible pump 05T-3085 - Fin mounted
24 position rosette pylon Sea-Bird SBE-32 4 way rosette pylon on NMF 24 way frame 32-19817-0243 - Equipped with 24 10 litre external spring Niskin sampling bottles
CTD deck unit Sea-Bird 11plus deck unit with Powertecnique UPS 11P-34173-0676 - -
CTD deck unit Sea-Bird 11plus deck unit 11P-24680-0589 - Spare unit
Pressure transducer Digiquartz temperature compensated pressure sensor 73299 18/04/2008 -
Conductivity sensor Sea-Bird 4C conductivity sensor 04C-2580 10/09/2009 -
Temperature sensor Sea-Bird 3P temperature sensor 03P-4116 15/09/2009 -
Secondary conductivity sensor Sea-Bird 4C conductivity sensor 04C-3567 05/05/2009 Fin mounted
Secondary temperature sensor Sea-Bird 3P temperature sensor 03P-4383 07/05/2009 Fin mounted
Dissolved oxygen sensor Sea-Bird 43 dissolved oxygen sensor 43-0862 10/03/2009 9plus mounted
Fluorometer Chelsea MKIII Aquatracka fluorometer 09-7117-001 10/06/2009 -
Altimeter Benthos PSA-916T altimeter 41302 20/04/2007 -
Light scattering sensor WETLabs light scattering sensor BBRTD-182 20/06/2007 -
Transmissometer Chelsea MKII 25 cm path Alphatracka transmissometer 07-6075-001 18/10/2007 -
LADCP RDI WorkHorse Monitor 300 KHz 12920 - Down-looking master configuration
LADCP RDI WorkHorse Monitor 300 KHz 4275 - Up-looking slave configuration

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 .

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 .

BODC Processing

Conductivity, temperature, salinity and conductivity from the primary sensors were received in a structured matlab format and converted into BODC internal format. The auxiliary sensor data were not processed by the originators and will be loaded separately. Potential temperature of the water body was derived by computation using UNESCO 1983 algorithm, σθ was derived by computation from salinity and potential temperature also using UNESCO 1983 algorithm. In addition to the variables loaded, the matlab file also contained; conductivity, latitude, longitude and potential temperature. The following table shows how the variables within the matlab file were mapped to appropriate BODC parameter codes:

Originator's Parameter Name Units Description BODC Parameter Code Units Comments
temp °C Temperature from primary sensor TEMPS901 °C -
cond mS cm -1 Conductivity CNDCST01 S/m Conversion needed (/10)
sal1 - Practical salinity PSALCC01 Dimensionless Calibrated against CTD bottle salinity samples
pres dbar Pressure exerted by the water column PRESPR01 dbar -
- - Potential temperature POTMCV01 °C Generated by BODC using the Fofonoff and Millard (1983) algorithm
- - σθ of the water column SIGTPR01 kg m -3 Generated by BODC using the Fofonoff and Millard (1983) algorithm

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.

References

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.

Originator's Data Processing

Sampling Strategy

In total, 10 CTD stations were carried out, this included six CTD casts (CTD001 to CTD006) and four tow-yo casts (CTD007 to CTD010). The first two tow-yo casts (CTD007 to CTD008) were full-depth tow-yos with three up-and-down profiles each. The last two tow-yo casts (CTD009 to CTD010) were in shallow water with 14 and 24 up-and-down profiles respectively. Four casts (CTD003 to CTD006) were carried out in the location of the moorings deployments. In total, 94 profiles (including upcasts) were obtained with no major operational issues encountered.

Data processing

The files were produced by Seawave (v 7.18) and initial data processing was performed using SBE Data Processing, Version 7.19. Firstly, the raw data were converted into physical units using 'Data Conversion'. A temporal offset of 5 was then applied to align the oxygen sensor readings using 'Align CTD'. Offsets were not applied for primary and secondary temperature and salinity, as the CTD deck unit automatically applied the conductivity lag to the conductivity sensors. Corrections for the thermal mass of the cell were made using 'Cell Thermal Mass' and the output from the 'Align CTD', in order to minimise salinity spiking in steep vertical gradients due to temperature/conductivity mismatch. 'Filter' applied a low pass filter to the pressure channel, followed by 'Loop Edit' which applied flags to pressure reversals, where the package has slowed down or even stopped. After which, the surface soak was removed followed by 'Derive' which calculated primary and secondary salinity and oxygen concentrations.

After the Sea-Bird processing, further processing was undertaken using the National Oceanography Centre's Mstar software package using the MEXEC processing suite of programs. Firstly, sample (SAM) files were created to store all information about rosette bottle samples. The CTD data were then processed, with the data firstly averaged to 1 Hz, followed by the calculation of practical salinity and potential temperature. For the CTD casts, the downcast data were extracted to create a 2 db resolution file. Positions were loaded to from the navigation file. For the tow-yo casts each upward and downward profile was isolated and the data averaged and interpolated into a 2 db bins and then manually appended into one file.

Further details of the originator's processing can be found in the cruise report.

Field Calibrations

Salinity

Ninty eight from a total of 109 salinity samples from the CTD Niskin bottle samples were used to calibrate the CTD salinity data. A comparison of the primary and secondary sensors showed there to be drift in the second sensor seemingly linear in depth. Therefore, only data from the primary sensor were used for the calibration. In addition, the difference between CTD salinity and the bottle salinity was greater than usual with some discussion about the possible reasons given in the cruise report. The primary salinity data were calibrated but this calibration equation is unknown. The difference between the uncalibrated and calibrated salinity was determined to be +0.0013.


Project Information

Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) project document

DIMES is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.

The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing.

DIMES includes tracer release, isopycnal following RAFOS floats, microstructure measurements, shearmeter floats, EM-APEX floats, a mooring array in Drake Passage, hydrographic observations, inverse modeling, and analysis of altimetry and numerical model output.

DIMES is sponsored by the National Science Foundation (U.S.), Natural Environment Research Council (U.K) and British Antarctic Survey (U.K.)

For more information please see the official project website at DIMES


Data Activity or Cruise Information

Cruise

Cruise Name JC041 (UKD-1)
Departure Date 2009-12-05
Arrival Date 2009-12-21
Principal Scientist(s)Alberto C Naveira Garabato (University of Southampton School of Ocean and Earth Science)
Ship RRS James Cook

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