Metadata Report for BODC Series Reference Number 756847


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
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Stuart Cunningham
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) Rapid Climate Change Programme
RAPIDMOC
 

Data Identifiers

Originator's Identifier CTD304003
BODC Series Reference 756847
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2006-05-12 19:12
End Time (yyyy-mm-dd hh:mm) 2006-05-12 20:37
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 28.42600 N ( 28° 25.6' N )
Longitude 15.17800 W ( 15° 10.7' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 3.0 m
Maximum Sensor Depth 3043.0 m
Minimum Sensor Height 425.0 m
Maximum Sensor Height 3465.0 m
Sea Floor Depth 3468.0 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 Approximate - Depth is only approximate
 

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
CNDCST02 1 Siemens per metre CTDCond2 Electrical conductivity of the water body by CTD (sensor 2)
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
PSALCC02 1 Dimensionless P_sal_CTD_calib2 Practical salinity of the water body by CTD (second sensor) 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
SIGTPR02 1 Kilograms per cubic metre SigTheta2 Sigma-theta of the water body by CTD (second sensor) and computation from salinity and potential temperature using UNESCO algorithm
TEMPCU01 1 Degrees Celsius Uncal_CTD_Temp Temperature of the water body by CTD and NO verification against independent measurements
TEMPCU02 1 Degrees Celsius Uncal_CTD_Temp2 Temperature of the water body by CTD (second sensor) 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


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 .

Instrument Description

CTD unit and auxiliary sensors

The CTD system used on cruise D304 was the Sea-Bird 911 plus , with a Sea-Bird 32 carousel. Several of the Niskin bottles were removed from the frame, to accommodate moored instruments for calibration purposes. The CTD was fitted with the following scientific sensors:

Sensor Serial Number Last calibration date
Primary Temperature SBE-3P 2919 March 2006
Secondary Temperature SBE-3P 4116 March 2006
Primary Conductivity SBE-4C 3153 March 2006
Pressure-Digiquartz 94756 -
Oxygen- SBE 43 0612 -

The salinity samples from the CTD were analysed during the cruise using the Guildline Autosal model 8400B (serial number 68426). The Autosal was standardised using batch P144 IAPSO Standard Seawater .

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 .

BODC Processing

The data arrived at BODC in 10 PSTAR format files representing all of the CTD casts conducted during the D304 cruise. These were reformatted to the internal QXF format using BODC transfer function 360. The following table shows how the variables within the .MAT files were mapped to appropriate BODC parameter codes:

Originator' Variable Units Description BODC Parameter Code Units Comments
Pressure dbar Pressure exerted by the water column PRESPR01 dbar Manufacturer's calibration applied.
Temperature (Primary) °C Temperature of the water column by CTD TEMPCC01 °C Calibrated by data originator
Temperature (Secondary) °C Temperature of the water column by CTD TEMPCC02 °C Calibrated by data originator
Salinity (Primary) - Practical salinity of the water column PSALCC01 - Calibrated by data originator with discrete salinity samples.
Salinity (Secondary) - Practical salinity of the water column PSALCC02 - Calibrated by data originator with discrete salinity samples.
Sigma-theta Primary (UNESCO SVAN) Kg m -3 Density of the water column SIGTPR01 Kg m -3 Calculated using the Fofonoff and Millard (1982) algorithm
Sigma-theta Secondary (UNESCO SVAN) Kg m -3 Density of the water column SIGTPR02 Kg m -3 Calculated using the Fofonoff and Millard (1982) algorithm
Potential Temperature (Primary) °C Density of the water column POTMCV01 °C Not transferred
Potential Temperature (Secondary) °C Potential temperature of the water column POTMCV01 °C Not transferred
Conductivity (Primary) mS/cm Electrical conductivity of the water column CNDCST01 S/m /10
Conductivity (Secondary) mS/cm Electrical conductivity of the water column CNDCST02 S/m /10
Latitude ° Latitude North ALATGP01 ° Not transferred
Longitude ° Longitude East ALONGP01 ° Not transferred

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, and missing data marked by both setting the data to an appropriate value and setting the quality control flag.

Originator's Data Processing

Sampling Strategy

A total of 10 CTD casts were perfomed during the cruise along the Eastern boundary and Mid Atlantic Ridge sections of the 26.5N RAPIDMOC array. The CTD casts provided start-point calibrations for instruments to be deployed and end-point calibrations for recovered instruments. For recovered instruments that were re-deployed, the post-deployment cast provided a pre-deployment calibration. The instruments were set to the fastest sampling rate and the CTD lowered as normal. On the upcast, the bottle stops were increased to 5 minutes to allow time for stabilisation and the provision of more accurate data. To allow the instruments to be attached to the CTD frame using bespoke attachments, 12 sample bottles were removed on all but the tenth and final cast, when 20 sample bottles were removed.

Data Processing

Raw CTD data were transferred from the SeaBird deck unit to a PC via SeaBird software (Seasave Win32 version 5.35). Physical units were calculated from the frequency data using the manufacturer's calibration routines and the data converted to ASCII format. The ASCII files were converted to PSTAR format and in-house programs were run to reduce the frequency of the data from 24Hz to 1Hz, and for the downcast to be averaged to a 2db pressure grid. A calibration was produced for the CTD conductivity sensor by merging the salinity sample data with the CTD data

Field Calibrations

Independent salinity samples, obtained from the CTD rosette, were used to calibrate the CTD salinity data. Bottle samples with incorrect conductivities were identified and removed from the calibration. Data were initially rejected where the ratio K= {C bot /C CTD } exceeded the limits 0.999 - 1.001 (where {} denotes station average) and also +/- 3 standard deviations of the new station mean.

A second order polynomial was fitted to K versus C bot : K=1.007+4.0652e-07xC bot + 4.0652e-07x C bot 2 and CTD corrected=C CTD *K.

A second order polynomial was then applied to K versus station number in order to calculate a final station-by station correction: K2=1.0001-3.8463e-05xC bot + 3.168e-06x C bot 2 and CTD corrected=C CTD *K2.

References

Baringer, M.O., Kanzow, T. and et al, .Rayner, D. (ed.) (2007) 'Cruise Report No. 16 RV Ronald H. Brown Cruise RB0602 and RRS Discovery Cruise D304'

- available online here


Project Information

Rapid Climate Change (RAPID) Programme

Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council (NERC). The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

Scientific Objectives

Projects

Overall 38 projects have been funded by the RAPID programme. These include 4 which focus on Monitoring the Meridional Overturning Circulation (MOC), and 5 international projects jointly funded by the Netherlands Organisation for Scientific Research, the Research Council of Norway and NERC.

The RAPID effort to design a system to continuously monitor the strength and structure of the North Atlantic Meridional Overturning Circulation is being matched by comparative funding from the US National Science Foundation (NSF) for collaborative projects reviewed jointly with the NERC proposals. Three projects were funded by NSF.

A proportion of RAPID funding as been made available for Small and Medium Sized Enterprises (SMEs) as part of NERC's Small Business Research Initiative (SBRI). The SBRI aims to stimulate innovation in the economy by encouraging more high-tech small firms to start up or to develop new research capacities. As a result 4 projects have been funded.


Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)

Scientific Rationale

There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). As a consequence of the MOC northwest Europe enjoys a mild climate for its latitude: however abrupt rearrangement of the Atlantic Circulation has been shown in climate models and in palaeoclimate records to be responsible for a cooling of European climate of between 5-10°C. A principal objective of the RAPID programme is the development of a pre-operational prototype system that will continuously observe the strength and structure of the MOC. An initiative has been formed to fulfill this objective and consists of three interlinked projects:

The entire monitoring array system created by the three projects will be recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2014 the array will continue to be serviced annually under RAPID-WATCH funding.

The array will be focussed on three regions, the Eastern Boundary (EB), the Mid Atlantic Ridge (MAR) and the Western Boundary (WB). The geographical extent of these regions are as follows:

References

Baehr, J., Hirschi, J., Beismann, J.O. and Marotzke, J. (2004) Monitoring the meridional overturning circulation in the North Atlantic: A model-based array design study. Journal of Marine Research, Volume 62, No 3, pp 283-312.

Baringer, M.O'N. and Larsen, J.C. (2001) Sixteen years of Florida Current transport at 27N Geophysical Research Letters, Volume 28, No 16, pp3179-3182

Bryden, H.L., Johns, W.E. and Saunders, P.M. (2005) Deep Western Boundary Current East of Abaco: Mean structure and transport. Journal of Marine Research, Volume 63, No 1, pp 35-57.

Hirschi, J., Baehr, J., Marotzke J., Stark J., Cunningham S.A. and Beismann J.O. (2003) A monitoring design for the Atlantic meridional overturning circulation. Geophysical Research Letters, Volume 30, No 7, article number 1413 (DOI 10.1029/2002GL016776)


Data Activity or Cruise Information

Cruise

Cruise Name D304
Departure Date 2006-05-12
Arrival Date 2006-06-06
Principal Scientist(s)Torsten Kanzow (National Oceanography Centre, Southampton)
Ship RRS Discovery

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