Metadata Report for BODC Series Reference Number 670827


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Neil Brown MK3 CTD  CTD; water temperature sensor; salinity sensor; dissolved gas sensors
Chelsea Technologies Group Alphatracka transmissometer  transmissometers
National Marine Facilities Microelectrode Oxygen Sensor  dissolved gas sensors
Chelsea Technologies Group Aquatracka III fluorometer  fluorometers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Ms Jane Read
Originating Organization Southampton Oceanography Centre (now National Oceanography Centre, Southampton)
Processing Status banked
Project(s) -
 

Data Identifiers

Originator's Identifier CTD14000
BODC Series Reference 670827
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2001-05-14 03:35
End Time (yyyy-mm-dd hh:mm) 2001-05-14 04:38
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 60.41033 N ( 60° 24.6' N )
Longitude 19.03533 W ( 19° 2.1' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 0.99 m
Maximum Sensor Depth 2517.48 m
Minimum Sensor Height 20.42 m
Maximum Sensor Height 2536.92 m
Sea Floor Depth 2537.91 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 Instantaneous - Depth measured below water line or instantaneous water body surface
 

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
CPHLPR01 1 Milligrams per cubic metre chl-a_water_ISfluor 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
DOXYZZ01 1 Micromoles per litre WC_dissO2_IS Concentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ sensor
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

Quality report - D253 Pascal Oxygen sensor data

From visualising the data it is clear that the Pascal Oxygen sensor did not perform well during this cruise. This channel was not calibrated against bottle samples and from the values they appear either far too low or far too high. Therefore all the data from this Oxygen sensor have been flagged 'M' by BODC and consequently the derived Oxygen saturation channel has been flagged too.

CTD casts that included a Pascal Oxygen sensor -


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

National Marine Facilities Microelectrode Oxygen Sensor

The Microelectrode Oxygen Sensor is a non-membrane dissolved oxygen sensor developed by the Ocean Engineering Division of National Marine Facilities (NMF) at the National Oceanography Centre, and the Electro-Chemistry Group at the University of Southampton Chemistry Department. The sensor is suitable for marine applications. It was first used in 2000 and development is ongoing.

The fundamental parts of the sensor are a platinum microelectrode and a counter electrode (thus far composed of copper). A measurement potential is applied to the microelectrode relative to the counter electrode. This leads to reduction of dissolved oxygen at the microelectrode and produces a current proportional to the number of oxygen molecules at that electrode.

The sensor is suitable for operation on a CTD system as it is free from the pressure effects (e.g. slow response, drift and hysteresis) typically encountered when using oxygen sensors that employ a membrane. Its short response time (approximately 1 second) also makes it suitable for deployment on CTDs and oceanographic undulators. The sensor includes both analogue voltage and serial digital (RS 232) outputs.

The electrode surface is reconditioned by applying a cleaning potential to the microelectrode at which oxidation occurs. This minimises drift and the effects of bio-fouling.

Ongoing development

Early versions of the instrument applied the measurement potential for up to 30 seconds, with sampling starting approximately one second after the potential was applied. The sensor response to oxygen remained almost constant for a given concentration and data could be sampled at frequencies exceeding 1 Hz.

However, the sensor proved to be very sensitive to fluctuations in flow, leading to apparent noise in the data. In an attempt to address this, various changes were made to the functionality:

Instrument Description

CTD Unit and Auxiliary Sensors

During this cruise, two separate CTD rigs with different sensors were deployed for different sections of the line.
CTD stations 13965 to 14026 used the Neil Brown Mk3 CTD and are called subaccession A
CTD stations 14027 to 14062 used the Sea-Bird 911 CTD are called subaccession B
CTD stations 14064 to 14130 used the Neil Brown Mk3 CTD and are called subaccession A

Sensor Serial Number Last calibration date Comments
Neil Brown Mk3 CTD unit with FSI rosette pylon 24 bottle IM960513 December 1999 Used for subaccession A deployments
Sea_Bird 911 CTD unit 09P24680-0636 No information Used for subaccession B deployments
Pylon: Sea-Bird 32 Carousel/24-bottle position 32-24680-0345 No information Used for subaccession B deployments
Chelsea Instruments Aquatracka 61/2642/003 No information Used for subaccession A deployments
Chelsea MKII Alphatracka 25cm path Transmissometer 161047 No information Used for subaccession B deployments
Chelsea MKIII Aquatracka Fluorimeter 88-2360-108 No information Used on both A and B deployments
Pascal Oxygen Sensor No information No information Used for subaccession A deployments
Sea-Bird SBE 43B dissolved oxygen sensor 43B-0008 No information Used for subaccession B deployments
Primary Premium Temperature Sensor 3P 03P-4107 No information Used for subaccession B deployments
Primary Conductivity Sensor 4C 04C-2573 No information Used for subaccession B deployments
Digiquartz Temperature Compensated Pressure Sensor 83008 No information Used for subaccession B deployments

Neil Brown MK3 CTD

The Neil Brown MK3 conductivity-temperature-depth (CTD) profiler consists of an integral unit containing pressure, temperature and conductivity sensors with an optional dissolved oxygen sensor in a pressure-hardened casing. The most widely used variant in the 1980s and 1990s was the MK3B. An upgrade to this, the MK3C, was developed to meet the requirements of the WOCE project.

The MK3C includes a low hysteresis, titanium strain gauge pressure transducer. The transducer temperature is measured separately, allowing correction for the effects of temperature on pressure measurements. The MK3C conductivity cell features a free flow, internal field design that eliminates ducted pumping and is not affected by external metallic objects such as guard cages and external sensors.

Additional optional sensors include pH and a pressure-temperature fluorometer. The instrument is no longer in production, but is supported (repair and calibration) by General Oceanics.

Specifications

These specification apply to the MK3C version.

Pressure Temperature Conductivity
Range

6500 m

3200 m (optional)

-3 to 32°C 1 to 6.5 S cm -1
Accuracy

0.0015% FS

0.03% FS < 1 msec

0.0005°C

0.003°C < 30 msec

0.0001 S cm -1

0.0003 S cm -1 < 30 msec

Further details can be found in the 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 .

Chelsea Technologies Group ALPHAtracka and ALPHAtracka II transmissometers

The Chelsea Technologies Group ALPHA tracka (the Mark I) and its successor, the ALPHA tracka II (the Mark II), are both accurate (< 0.3 % fullscale) transmissometers that measure the beam attenuation coefficient at 660 nm. Green (565 nm), yellow (590 nm) and blue (470 nm) wavelength variants are available on special order.

The instrument consists of a Transmitter/Reference Assembly and a Detector Assembly aligned and spaced apart by an open support frame. The housing and frame are both manufactured in titanium and are pressure rated to 6000 m depth.

The Transmitter/Reference housing is sealed by an end cap. Inside the housing an LED light source emits a collimated beam through a sealed window. The Detector housing is also sealed by an end cap. A signal photodiode is placed behind a sealed window to receive the collimated beam from the Transmitter.

The primary difference between the ALPHA tracka and ALPHA tracka II is that the Alphatracka II is implemented with surface-mount technology; this has enabled a much smaller diameter pressure housing to be used while retaining exactly the same optical train as in the Mark I. Data from the Mark II version are thus fully compatible with that already obtained with the Mark I. The performance of the Mark II is further enhanced by two electronic developments from Chelsea Technologies Group - firstly, all items are locked in a signal nulling loop of near infinite gain and, secondly, the signal output linearity is inherently defined by digital circuitry only.

Among other advantages noted above, these features ensure that the optical intensity of the Mark II, indicated by the output voltage, is accurately represented by a straight line interpolation between a reading near full-scale under known conditions and a zero reading when blanked off.

For optimum measurements in a wide range of environmental conditions, the Mark I and Mark II are available in 5 cm, 10 cm and 25 cm path length versions. Output is default factory set to 2.5 volts but can be adjusted to 5 volts on request.

Further details about the Mark II instrument are available from the Chelsea Technologies Group ALPHA tracka II specification sheet .

BODC Processing

The CTD data were supplied to BODC in 156 PStar files and converted to the BODC internal format, a netCDF subset.

During transfer the originator's variables were mapped to unique BODC parameter codes. The following table shows the parameter mapping. During the cruise, two separate CTD rigs were employed for different sections of the line:- a Neil Brown CTD and a Sea-Bird CTD, which in some cases had different sensors measuring the same quantity. CTD casts recorded by the Neil Brown CTD are identified as subaccession A, those recorded by the Sea-Bird CTD are subaccession B. Where the same originator's variable in the source files was recorded by different sensors on different CTD rigs (possibly resulting in a different BODC parameter mapping) this has been made clear in the table below.

Originator's variable Units Description BODC Code Units Comments
time - Time - - Not transferred - will be superseded in BODC processing
press db Pressure (spatial co-ordinate) exerted by the water body by profiling pressure sensor and corrected to read zero at sea level. PRESPR01 db -
temp °C Temperature of the water body by CTD or STD TEMPST01 °C -
cond Subacc A: mmho/cm
Subacc B: mS/cm
Electrical conductivity of the water body by CTD CNDCST01 S/m cond divided by 10 for subacc A and B
salinity psu Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm PSALST01 Dimensionless -
fluor Subacc A: mg/m 3
Subacc B: volts
Subacc A: Concentration of chlorophyll-a {chl-a} per unit volume of the water body [particulate >unknown phase] by in-situ chlorophyll fluorometer
Subacc B: Instrument output (voltage) by in-situ Aquatracka chlorophyll fluorometer
Subacc A: CPHLPR01
Subacc B: FVLTAQ01
Subacc A: mg/m 3
Subacc B: Volts
-
tran Subacc A: percent
Subacc B: volts
Subacc A: Transmittance (red light wavelength) per 25cm of the water body by 25cm path length red light transmissometer
Subacc B: Instrument output (voltage) by 25cm path length red light transmissometer
Subacc A: POPTDR01
Subacc B: TVLTDR01
Subacc A: percent
Subacc B: volts
-
oxygen Subacc A: µmol/l
Subacc B: ml/l
Concentration of oxygen {O2} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ sensor DOXYZZ01 Micromoles per litre Unit conversion handled automatically by transfer for both subaccessions
- - Saturation of oxygen {O2} in the water body OXYSSC01 % Calculated by the BODC transfer
- - Potential temperature of the water body by computation using UNESCO 1983 algorithm POTMCV01 Degrees Celsius Calculated by the BODC transfer
- - Sigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm SIGTPR01 Kilograms per cubic metre Calculated by the BODC transfer

Following transfer the data were screened using BODC in-house visualisation software. A small number of suspect data values were identified during screening and assigned a BODC data quality flag.

Originator's Data Processing

Sampling strategy

The FISHES 2001 (DI253) cruise repeated the occupation of a number of hydrographic lines between Scotland and Iceland and carried out detailed multidisciplinary surveys of the northern ends of the Iceland Basin (including the Iceland Faeroes Front - IFF) and Rockall Trough to resolve both basin- and meso-scale physical, chemical and biological structure. In total, 156 CTD casts were completed.

Data Acquisition and Initial Processing

The data were processed using PEXEC (pstar) routines. Further details on the processing can be found in the cruise report . The data were calibrated post-cruise.

The processed data, together with the raw Sea-Bird, configuration and bottle files, were supplied to BODC for banking.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name D253
Departure Date 2001-05-04
Arrival Date 2001-06-20
Principal Scientist(s)John T Allen (Southampton Oceanography Centre)
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