Metadata Report for BODC Series Reference Number 971810


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
Chelsea Technologies Group Aquatracka fluorometer  fluorometers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Harry Leach
Originating Organization University of Liverpool Department of Earth Sciences (now University of Liverpool Department of Earth, Ocean and Ecological Sciences)
Processing Status banked
Project(s) WOCE
UK WOCE
 

Data Identifiers

Originator's Identifier CTD12v08
BODC Series Reference 971810
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1991-05-27 01:25
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 51.08967 N ( 51° 5.4' N )
Longitude 28.11433 W ( 28° 6.9' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 0.43 m
Maximum Sensor Depth 3630.13 m
Minimum Sensor Height 209.46 m
Maximum Sensor Height 3839.17 m
Sea Floor Depth 3839.6 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 Chart reference - Depth extracted from available chart
 

Parameters

BODC CODE Rank Units Short Title Title
ATTNZR01 1 per metre Atten_red Attenuation (red light wavelength) per unit length of the water body by transmissometer
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
POATCV01 1 per metre PotAtten Potential attenuance (unspecified wavelength) per unit length of the water body by transmissometer and computation using P-EXEC algorithm
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


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 .

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 .

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

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 58 and 59 CTD Data Documentation

Introduction

CTD profile data are presented from the VIVALDI '91 cruises Charles Darwin 58 and 59, as reported by Pollard et al. (1991). The data collection and calibration procedures have been described by Griffiths et al. (1992).

Instrumentation and Methodology

Instrumentation Summary

The CTD profiles were taken with a Neil Brown Systems MkIIIb CTD mounted beneath a bottle rosette. The CTD was fitted with a pressure sensor, conductivity cell, platinum resistance thermometer, a dissolved oxygen sensor, a Chelsea Instruments fluorometer, a Sea Tech 100cm path transmissometer and an IOS 10kHz pinger.

Data Acquisition

Lowering rates for the CTD package were generally in the range 0.5-1.0ms -1 but could be up to 1.5ms -1 . CTD data were logged at 16 frames per second. The CTD deck unit passes raw data to a dedicated Level A microcomputer where 1 second averages are assembled. During this process the Level A calculates the rate of change of temperature and a median sorting routine detects and removes pressure spikes. These data are sent to the Level B for archival. The data are then passed to a Level C workstation for conversion to Pstar format and calibration.

A total of 19 stations were occupied during CD58 (11v01 - 11v19) and 21 stations during CD59 (12v01 - 12v21) using the MkIIIb CTD. The first 2 stations of CD58 were equipment test stations not on the Vivaldi grid and the data have not been passed on to BODC. During CD59 a Neil Brown MkV CTD was also used at 3 of the stations (12v12 - not 12v11 as sometimes reported in the cruise report, 12v16 and 12v17), but these data were not forwarded to BODC and are not reported here.

Data Processing

The 1 second data passed to the Level C were converted to Pstar format and initially calibrated with coefficients from laboratory calibrations. The up cast data were extracted for merging with the bottle firing codes, on time, thus the CTD variables were reconciled with the bottle samples. Final calibrations were applied using the sample bottle data.

The data were worked up to WOCE standards by the data originators before being supplied to BODC. Although an oxygen sensor was fitted to the CTD, the data originators considered that these data were not to WOCE standards. Subsequently, the data are not reported here and are not stored by BODC.

BODC Data Processing

No further calibrations were applied to the data received by BODC. BODC were mainly concerned with the screening and banking of the data.

The CTD data were received as 1Hz pressure sorted down cast data. Parameters were pressure (dbar), temperature (°C), salinity (psu), chlorophyll-a (mg/m 3 ) and potential attenuance (/m).

The data were converted into the BODC internal format (PXF) to allow the use of in-house software tools, notably the graphics editor. Potential attenuance was converted to attenuance as follows:

atten = exp (-atten)
atten = atten / (1.0 -ln (atten) x press / 215800)
atten = -ln (atten)

Spikes in the data were manually flagged 'suspect' by modification of the associated quality control flag. In this way none of the original data values were edited or deleted during quality control. These data from the VIVALDI '91 cruises required little flagging and just a few points were set suspect. Chlorophyll was all null in profile 12v13.

Once screened, the CTD data were loaded into a database under the Oracle relational database management system. The start time is the CTD deployment time, and the end time is the time the CTD was removed from the water. Actually these times are more precisely the start and end of data logging. Latitude and longitude are the mean positions between the start and end times calculated from the master navigation in the binary merged file.

References

Griffiths, G. et al. (1992). CTD oxygen, tracer and nutrient data from RRS Charles Darwin Cruises 58/59 in the NE Atlantic as part of Vivaldi '91. Institute of Oceanographic Sciences Deacon Laboratory, Report No. 296, 52pp.

Pollard, R.T. et al. (1991). RRS Charles Darwin Cruises 58 & 59. Institute of Oceanographic Sciences Deacon Laboratory, Cruise Report No. 228, 49pp.


Project Information

World Ocean Circulation Experiment (WOCE)

The World Ocean Circulation Experiment (WOCE) was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate.

WOCE had two major goals:


UK WOCE

The UK made a substantial contribution to the international World Ocean Circulation Experiment (WOCE) project by focusing on two important regions:

  1. Southern Ocean - links all the worlds oceans, controlling global climate.
  2. North Atlantic - directly affects the climate of Europe.

A major part of the UK effort was in the Southern Ocean and work included:

In the North Atlantic the UK undertook:

Satellite ocean surface topography, temperature and wind data were merged with in situ observations and models to create a complete description of ocean circulation, eddy motion and the way the ocean is driven by the atmosphere.

The surveys were forerunners to the international Global Ocean Observing System (GOOS). GOOS was later established to monitor annual to decadal changes in ocean circulation and heat storage which are vital in the prediction of climate change.


Data Activity or Cruise Information

Cruise

Cruise Name CD59
Departure Date 1991-05-18
Arrival Date 1991-06-10
Principal Scientist(s)Harry Leach (University of Liverpool Department of Earth Sciences)
Ship RRS Charles Darwin

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameWOCE Atlantic Area 12 (AR12)
CategoryOffshore area
Latitude52° 0.00' N
Longitude18° 0.00' W
Water depth below MSL

World Ocean Circulation Experiment (WOCE) Atlantic Area 12 (AR12)

WOCE was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate. WOCE established numerous areas and repeat sections in the Atlantic Ocean as illustrated in the map below.

BODC image

AR12 spans the boundary between the subtropical and subpolar gyres in the eastern basin; stations lie within a box bounded by 40.0°N, 35.0°W at the southwest corner and 65.0°N, 03.0°W at the northeast corner The area was occupied between April 1991 to September 1998. A table of all AR12 cruises is presented below:

Cruise Cruise dates Country
Charles Darwin 58 1991-04-25 to 1991-05-15 UK
Charles Darwin 59 1991-05-18 to 1991-06-10 UK
Charles Darwin 62 1991-08-01 to 1991-09-04 UK
Pelagia 95 1995-07-18 to 1995-08-14 Netherlands
Pelagia 96 1996-06-18 to 1996-07-15 Netherlands
Discovery 223 1996-09-28 to 1996-11-18 UK
Meteor 39 1997-05-15 to 1997-06-07 Germany
Pelagia 110 1997-08-08 to 1997-08-29 Netherlands
Pelagia 122 1998-08-18 to 1998-09-02 Netherlands

Other Series linked to this Fixed Station for this cruise - 971686 971698 971705 971717 971729 971730 971742 971754 971766 971778 971791 971809 971822 971834 971846 971858 971871

Other Cruises linked to this Fixed Station (with the number of series) - CD58 (17) CD62 (95) D223A (57) D223B (28)


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