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Metadata Report for BODC Series Reference Number 380671


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
SeaTech transmissometer  transmissometers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Institute of Oceanographic Sciences Deacon Laboratory (now National Oceanography Centre, Southampton)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) -
 

Data Identifiers

Originator's Identifier CTD50006
BODC Series Reference 380671
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1990-07-13 03:51
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 60.83830 N ( 60° 50.3' N )
Longitude 13.43000 W ( 13° 25.8' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 0.99 m
Maximum Sensor or Sampling Depth 1628.88 m
Minimum Sensor or Sampling Height 38.11 m
Maximum Sensor or Sampling Height 1666.01 m
Sea Floor Depth 1667.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling 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 CODERankUnitsTitle
DOXYPR011Micromoles per litreConcentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ Beckmann probe
PPOPPR011PercentPotential transmittance (red light wavelength) per unit length of the water body by red light transmissometer and correction to a path length of 1m and for seawater compressibility
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALPR011DimensionlessPractical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPST011Degrees CelsiusTemperature 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

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."


Narrative Documents

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.

SeaTech Transmissometer

Introduction

The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.

Specifications

  • Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
  • Beam diameter: 15 mm
  • Transmitted beam collimation: <3 milliradians
  • Receiver acceptance angle (in water): <18 milliradians
  • Light source wavelength: usually (but not exclusively) 660 nm (red light)

Notes

The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.

A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.

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

RRS Charles Darwin Cruise 50 CTD Data Documentation

Introduction

Documentation for CTD data collected on RRS Charles Darwin Cruise 50 (June - July 1990) by the Institute of Oceanographic Sciences (Deacon Laboratory), Godalming, Surrey, UK, under the direction of P.M. Saunders.

Instrumentation

The instrument used was a Neil Brown Systems CTD which measured pressure, temperature and conductivity and was fitted with a Beckman dissolved oxygen electrode. The CTD was used alongside a General Oceanics Rosette Multisampler with 12 water bottles, a 10kHz pinger, a bottom echo-sounder and a SeaTech 1m path transmissometer. Lowering and retrieval rates of 0.5 to 1.5m/s were employed and the sensors were flushed with distilled water on recovery. Bottle samples and reversing thermometer measurements were made on ascent and sea water samples were analysed using a Guildline Autolab Salinometer.

Calibration

Pressure

The pre-calibration data for Charles Darwin 50 for pressure was obtained at a temperature of 20 °C on 10 May 1990 and was as follows:

P = 0.099662 * PRAW - 4.28E-7 * PRAW2 - 4.3

The calibration was obtained for increasing pressure and hence applies strictly to the downcast. The goodness of fit was 0.8 dbars and the deadweight employed was certified to an accuracy of 0.03 per cent full scale (i.e. 1.8 dbar at 6000 dbar). In the ocean, because of varying temperature, the following correction is applied:

PCOR = P - 0.39 (t1 -9)

where t1 is a lagged temperature, in °C, constructed from the CTD temperature data using a first order equation with a time constant of 400 seconds. This time constant and the temperature sensitivity of the pressure offset, 0.39 °C/dbar, were determined by laboratory trials. On the upcast, a further correction is made for the hysteresis of the pressure sensor (which can reach 5 dbar), again determined from laboratory measurements.

Temperature

The pre-cruise calibration for the temperature sensor, conducted with only partial immersion of the instrument, was found on 9 May 1990 as:

T = 0.9987 * TRAW - 0.014.

The goodness of fit of a 6 point calibration between 0.7 and +25 °C, was 0.5 milliK. Temperatures are given in the above calibration in °C on the ITS90 scale, which differ significantly from the IPTS68 scale only at the high end of the environmental temperatures (Saunders, 1990). For this cruise data comparisons may be made with earlier measurements without reference to the change in scale.

The mismatch between the slower time constant of the temperature sensor and the fast response of the conductivity sensor, which leads to salinity spikes, has been dealt with by correcting the temperature according to Procedure 1 described in Chapter 5 of the SCOR Working Group Report (Crease et al, 1988). A time constant of 0.25 seconds is assumed.

Comparisons were made with 7 digital reversing thermometers manufactured and calibrated by SIS, Kiel, Germany, and operated on the upcast by Niskin bottle closure in the usual manner. The mean difference of the 217 comparisons was -2.3 milliK with a standard error of ±0.8 milliK. The individual differences reveal that at pressures exceeding 500 dbars the differences tend to average closer to -5 milliK (with the reversing thermometers showing higher temperatures on average).

Conductivity/Salinity

On Station 1 the conductivity sensor failed and was replaced on retrieval, so no CTD salinities were obtained on this station. For stations 2 to 21 and 22 to 57 unique but different cell factors were used in calculating salinity for the CTD, i.e. 0.999535 and 0.9955 respectively (for p=0, T=15). The cell factor was assumed to vary with pressure and temperature in the manner described in the SCOR WG 51 report (Crease et al, 1988) with nominal values employed for the temperature expansion and pressure contraction coefficients of the cell material.

From the sample salinities measured on each station values of the apparent salinity difference SCTD - Ssample were constructed, where SCTD is the estimate taken on the upcast when stopped. A time series plot of the apparent salinity difference revealed slow drifts and small jumps in the CTD conductivity sensor response. Adjustments were made to CTD salinities, on a station by station basis. Despite, or perhaps because of, employing a brand new cell, the calibration drifted approximately 0.015 (in practical salinity units) during stations 2 to 21, then jumped 0.03; it remained stable for the rest of the cruise. After adjustment, the salinity differences were plotted as a function of pressure. No significant trend was found and the rms scatter around zero mean difference for the 490 comparisons was 0.0022.

Oxygen

CTD oxygen values were calculated using a standard algorithm found in Owens and Millard (1985). Parameters required from the CTD were selected on the downcast at the pressure corresponding to the upcast sample. A non- linear regression between these CTD parameters and the sample oxygen was performed: for this purpose the data set was divided into two approximately equal parts. No significant differences were found for each half of the data for the coefficient of temperature dependence (alpha), the coefficient of pressure dependence (beta) and fraction (the mix of ambient and oxygen cell temperatures). Values determined were alpha = -0.04148, beta = 0.000165 and fraction = 0.512. Both oxygen current lag and bias were set to zero, since non-zero values did not improve the fit. The cell factor was determined as 1.467. All of these values were used for the initial CTD oxygen determinations.

A time series plot of the apparent oxygen difference, OCTD - Osamp, revealed drifts and jumps. Adjustments were made to the CTD oxygens on a station by station basis. The range of adjustments is from -0.34 to 0.17 ml/l (i.e. about 0.5 ml/l). After adjustment, the individual oxygen differences were plotted versus pressure; the rms scatter around zero mean difference for the 490 comparisons was 0.08 ml/l (3.5 micromol/kg).

Transmittance

Potential transmittance, which takes account of the increasing mass of clear water in the 1 metre path of the instrument with increasing pressure, was calculated.

Data Processing

Original values were averaged over an interval of one second and calibration coefficients and correction factors applied.

Differences between successive values of each parameter were examined; the mean difference and its standard deviation calculated and values greater than several standard deviations from the mean difference were checked. Only a limited amount of editing of the data was required. Data were sorted on pressure, averaged at 2 dbars and missing values were interpolated. Derived quantities were computed from algorithms published by Fofonoff and Millard (1983).

References

Crease, J. et. al. 1988.
The acquisition, calibration and analysis of CTD data. UNESCO Technical Papers in Marine Science. No. 54, 96pp.

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

Owens, W.B. and Millard, R.C. 1985.
A new algorithm for CTD oxygen calibration. Journal of Physical Oceanography, 15, 621-631.

Saunders, P.M. 1990.
The International Temperature Scale 1990, ITS90. WOCE Newsletter No. 10, p10 (Unpublished Manuscript).

Saunders, P.M., Gould, W.G., Hydes, D.J. and Brandon, M.A. 1991.
CTDO and nutrient data from Charles Darwin Cruise 50 in the Iceland Faeroes region. Institute of Oceanographic Sciences Deacon Laboratory, Report No. 282, 74pp.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name CD50
Departure Date 1990-06-29
Arrival Date 1990-07-22
Principal Scientist(s)W John Gould (Institute of Oceanographic Sciences Deacon Laboratory)
Ship RRS Charles Darwin

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameLousy Bank - Iceland Repeat Section: Station IB05
CategoryOffshore location
Latitude60° 50.62' N
Longitude13° 25.40' W
Water depth below MSL1657.0 m

Lousy Bank - Iceland Repeat Section: Station IB05

Lousy Bank - Iceland Station IB05 is one of 20 fixed CTD stations, which together form the Lousy Bank - Iceland repeat survey line.

Related Fixed Station activities are detailed in Appendix 1

Fixed Station Information

Station NameLousy Bank - Iceland Repeat Section
CategoryOffshore route/traverse

Lousy Bank - Iceland Repeat Section

The Lousy Bank - Iceland Repeat Section comprises 20 fixed CTD stations. The Section was first visited in 1962 and three subsequent research cruises during the 1990s.

Map of standard Lousy Bank - Iceland CTD Stations

BODC image

Map produced using the GEBCO Digital Atlas.

The white triangles indicate the nominal positions of each standard station on the Lousy Bank - Iceland Section.

Nominal station details

Lousy Bank - Iceland

Station Nominal latitude Nominal longitude Approx.
depth (m)
Comment
IB01 60° 29.06' N 12° 41.81' W 406 Lousy Bank
IB02 60° 33.7' N 12° 52.92' W 598  
IB03 60° 39.19' N 13° 2.62' W 1037  
IB04 60° 44.32' N 13° 13.14' W 1444  
IB05 60° 50.62' N 13° 25.4' W 1657  
IB06 60° 55.1' N 13° 35.73' W 1666  
IB07 61° 7.93' N 14° 6.22' W 1765  
IB08 61° 23.51' N 14° 35.2' W 2073  
IB09 61° 36.15' N 15° 6.74' W 2150  
IB10 61° 49.98' N 15° 35.77' W 2279  
IB11 62° 3.27' N 16° 3.84' W 2230  
IB12 62° 17.56' N 16° 18.7' W 2136  
IB13 62° 30.11' N 16° 33.21' W 2059  
IB14 62° 41.6' N 16° 48.09' W 1818  
IB15 62° 48.32' N 16° 55.35' W 1675  
IB16 62° 53.87' N 17° 0.68' W 1544  
IB17 63° 0.56' N 17° 7.81' W 1278  
IB18 63° 6.24' N 17° 15.14' W 1168  
IB19 63° 12.33' N 17° 21.77' W 688  
IB20 63° 15.72' N 17° 25.84' W 185 Iceland

Related Fixed Station activities are detailed in Appendix 2


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
B nominal value
Q value below limit of quantification

Appendix 1: Lousy Bank - Iceland Repeat Section: Station IB05

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Series IdentifierData CategoryStart date/timeStart positionCruise
1071207CTD or STD cast1999-09-23 08:42:0060.84367 N, 13.42333 WRRS Discovery D242
1252586Water sample data1999-09-23 09:10:0060.84367 N, 13.42333 WRRS Discovery D242

Appendix 2: Lousy Bank - Iceland Repeat Section

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Series IdentifierData CategoryStart date/timeStart positionCruise
380578CTD or STD cast1990-07-12 19:40:0060.4833 N, 12.6983 WRRS Charles Darwin CD50
380609CTD or STD cast1990-07-12 21:18:0060.5617 N, 12.885 WRRS Charles Darwin CD50
380622CTD or STD cast1990-07-12 23:19:0060.65 N, 13.05 WRRS Charles Darwin CD50
380646CTD or STD cast1990-07-13 01:25:0060.7367 N, 13.22 WRRS Charles Darwin CD50
380695CTD or STD cast1990-07-13 06:27:0060.9183 N, 13.6033 WRRS Charles Darwin CD50
380714CTD or STD cast1990-07-13 10:01:0061.1317 N, 14.1083 WRRS Charles Darwin CD50
380738CTD or STD cast1990-07-13 13:55:0061.3883 N, 14.5933 WRRS Charles Darwin CD50
380763CTD or STD cast1990-07-13 18:12:0061.605 N, 15.1133 WRRS Charles Darwin CD50
380787CTD or STD cast1990-07-13 21:58:0061.8283 N, 15.6017 WRRS Charles Darwin CD50
380806CTD or STD cast1990-07-14 07:14:0062.0617 N, 16.06 WRRS Charles Darwin CD50
380831CTD or STD cast1990-07-14 10:33:0062.2967 N, 16.315 WRRS Charles Darwin CD50
380855CTD or STD cast1990-07-14 15:40:0062.5 N, 16.5617 WRRS Charles Darwin CD50
380879CTD or STD cast1990-07-14 18:25:0062.6883 N, 16.79 WRRS Charles Darwin CD50
380892CTD or STD cast1990-07-14 20:43:0062.805 N, 16.9017 WRRS Charles Darwin CD50
380923CTD or STD cast1990-07-14 23:12:0062.9 N, 17.015 WRRS Charles Darwin CD50
380947CTD or STD cast1990-07-15 01:50:0063.0067 N, 17.135 WRRS Charles Darwin CD50
380984CTD or STD cast1990-07-15 07:14:0063.2 N, 17.3683 WRRS Charles Darwin CD50
1071060CTD or STD cast1999-09-19 03:53:0063.262 N, 17.43067 WRRS Discovery D242
1252433Water sample data1999-09-19 04:01:0063.262 N, 17.43067 WRRS Discovery D242
1071072CTD or STD cast1999-09-19 06:45:0063.20533 N, 17.36283 WRRS Discovery D242
1252445Water sample data1999-09-19 07:00:0063.20533 N, 17.36283 WRRS Discovery D242
1071084CTD or STD cast1999-09-19 09:48:0063.104 N, 17.25233 WRRS Discovery D242
1252457Water sample data1999-09-19 10:14:0063.104 N, 17.25233 WRRS Discovery D242
1071096CTD or STD cast1999-09-19 13:08:0063.00933 N, 17.13017 WRRS Discovery D242
1252469Water sample data1999-09-19 13:32:0063.00933 N, 17.13017 WRRS Discovery D242
1071103CTD or STD cast1999-09-20 06:21:0062.89783 N, 17.01133 WRRS Discovery D242
1252470Water sample data1999-09-20 06:47:0062.89783 N, 17.01133 WRRS Discovery D242
1071115CTD or STD cast1999-09-20 09:49:0062.80533 N, 16.9225 WRRS Discovery D242
1252482Water sample data1999-09-20 10:23:0062.80533 N, 16.9225 WRRS Discovery D242
1071871CTD or STD cast1999-09-20 13:54:0062.69333 N, 16.80167 WRRS Discovery D242
1252494Water sample data1999-09-20 14:23:0062.69333 N, 16.80167 WRRS Discovery D242
1071127CTD or STD cast1999-09-20 18:17:0062.50183 N, 16.5535 WRRS Discovery D242
1252501Water sample data1999-09-20 18:51:0062.50183 N, 16.5535 WRRS Discovery D242
1071139CTD or STD cast1999-09-20 22:47:0062.29267 N, 16.31167 WRRS Discovery D242
1252513Water sample data1999-09-20 23:26:0062.29267 N, 16.31167 WRRS Discovery D242
1071140CTD or STD cast1999-09-21 04:04:0062.05433 N, 16.064 WRRS Discovery D242
1252525Water sample data1999-09-21 04:40:0062.05433 N, 16.064 WRRS Discovery D242
1071152CTD or STD cast1999-09-22 11:44:0061.83283 N, 15.59617 WRRS Discovery D242
1252537Water sample data1999-09-22 12:19:0061.83283 N, 15.59617 WRRS Discovery D242
1071883CTD or STD cast1999-09-22 17:14:0061.6025 N, 15.11233 WRRS Discovery D242
1252549Water sample data1999-09-22 17:47:0061.6025 N, 15.11233 WRRS Discovery D242
1071164CTD or STD cast1999-09-22 21:39:0061.39183 N, 14.58667 WRRS Discovery D242
1252550Water sample data1999-09-22 22:11:0061.39183 N, 14.58667 WRRS Discovery D242
1071176CTD or STD cast1999-09-23 02:11:0061.13217 N, 14.10367 WRRS Discovery D242
1252562Water sample data1999-09-23 02:40:0061.13217 N, 14.10367 WRRS Discovery D242
1071188CTD or STD cast1999-09-23 05:58:0060.91833 N, 13.59567 WRRS Discovery D242
1252574Water sample data1999-09-23 06:26:0060.91833 N, 13.59567 WRRS Discovery D242
1071207CTD or STD cast1999-09-23 08:42:0060.84367 N, 13.42333 WRRS Discovery D242
1252586Water sample data1999-09-23 09:10:0060.84367 N, 13.42333 WRRS Discovery D242
1071219CTD or STD cast1999-09-23 11:58:0060.73867 N, 13.219 WRRS Discovery D242
1252598Water sample data1999-09-23 12:23:0060.73867 N, 13.219 WRRS Discovery D242
1071220CTD or STD cast1999-09-23 14:16:0060.65317 N, 13.04367 WRRS Discovery D242
1252605Water sample data1999-09-23 14:37:0060.65317 N, 13.04367 WRRS Discovery D242
1071232CTD or STD cast1999-09-23 16:24:0060.56167 N, 12.88217 WRRS Discovery D242
1252617Water sample data1999-09-23 16:42:0060.56167 N, 12.88217 WRRS Discovery D242
1071244CTD or STD cast1999-09-23 18:13:0060.48433 N, 12.69683 WRRS Discovery D242
1252629Water sample data1999-09-23 18:22:0060.48433 N, 12.69683 WRRS Discovery D242