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Metadata Report for BODC Series Reference Number 908245


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
Instrument Mounting research vessel
Originating Country Germany
Originator Prof Wolfgang Balzer
Originating Organization University of Bremen, Center for Marine Environmental Sciences
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) OMEX I
 

Data Identifiers

Originator's Identifier 149404
BODC Series Reference 908245
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1994-01-14 06:55
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 49.01000 N ( 49° 0.6' N )
Longitude 13.77333 W ( 13° 46.4' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth 2.97 m
Maximum Sensor or Sampling Depth 4435.58 m
Minimum Sensor or Sampling Height 32.42 m
Maximum Sensor or Sampling Height 4465.03 m
Sea Floor Depth 4468.0 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
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALST011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
SIGTPR011Kilograms per cubic metreSigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO 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.

FS Meteor 27_1 CTD Data Documentation

Instrumentation

The CTD profiles were taken with a Neil Brown Mk3 CTD incorporating a pressure sensor, conductivity cell, platinum resistance thermometers, dissolved oxygen sensor and a rosette sampler equipped with 12 Niskin bottles (12 litre). The CTD unit was mounted vertically in the centre of a protective cage. A 25cm path length transmissometer was attached to the rig.

Please note that neither the oxygen sensor nor the transmissometer functioned properly on this cruise. This was mentioned in the cruise report and has been confirmed by BODC inspection of the data. These channels have therefore been jettisoned.

Data Acquisition and On-Board Data Processing

The data were logged at 16 Hz on a PC running the standard EG&G data acquisition software. The CTDPOST software was used to apply nominal calibrations and output the data at full resolution as ASCII files. These were supplied to BODC.

Post-Cruise Processing

Reformatting

The ASCII data were transferred onto BODC's UNIX environment. The 16 Hz data were reduced to 1 Hz resolution by averaging the data from groups of 16 datacycles. A spike elimination algorithm prevented corruption of the generated 1 Hz data by any data dropout.

The output from the averaging program was combined with a time channel. The time channel was generated using the time in the file header as a base and assuming a 1 m/second lowering rate. Any gaps in the data stream could be detected and the time adjusted accordingly by monitoring the pressure channel.

Oxygen concentration was computed from the oxygen current and corrected for temperature and salinity using the standard Neil Brown algorithm. CTD temperature had to be used as the oxygen temperature channel data appeared corrupted. The resultant dissolved oxygen data were converted from ml/l to µM by multiplying the values by 44.66. However, as stated above, this was a vain effort and the oxygen data were discarded.

The data in ASCII format were then transferred to the BODC internal format. This allows the data to be quality assured using in-house software tools, notably the workstation graphics editor.

Editing

Using a custom in-house graphics editor, the limits of the downcasts were manually flagged. Upcasts were not saved. In addition, spikes on all the downcast channels were manually flagged 'suspect' by modification of the associated quality control flag. In this way none of the original data values were changed or lost.

Once screened on the workstation, the CTD downcasts were loaded into the OMEX database under the Oracle relational database management system and later migrated to the National Oceanographic Database.

Calibration

Pressure

The pressure offset was determined by looking at the pressures recorded when the CTD was clearly logging in air (readily apparent from the salinity channel). A consistent value was observed throughout the cruise and the following correction has been applied to the eight CTDs:

Pcorrected = Pobserved + 1.04

with the exception of cast 029401 (002-94/1) where the applied correction was 1.1 db.

Salinity and Temperature

The salinity was calibrated against 34 water bottle samples taken on 7 out of 16 casts. The bottle data for two of the casts (049401 and 069401) showed a significantly different offset from the other casts (approximately 0.02 rise in CTD salinity). After careful cross checking between these casts and other casts on the same station (OMEX 3) from other cruises it has been concluded that this apparent difference is the result of an error in the bottle data for these two casts.

Consequently, a single mean offset of -0.027 (standard deviation 0.0065) was determined for the whole cruise and this has been applied to the data.

No reversing thermometer readings were taken during the cruise due to the bad weather making the risk of smashing them too high. However, the temperature data from this CTD is reported as good quality and not usually in need of further calibration.

Oxygen

The oxygen converted to µM proved to be of suspicious quality, this probably being due to a corrupted current signal. The calibration against 45 water bottle samples was a total failure giving a correlation coefficient of 0.12. Therefore all the CTD oxygen data under ORACLE for this cruise were flagged as suspect.

Data Reduction

The final data set was produced by binning the calibrated data to 1 (casts shallower than 100 m) or 2 decibars. The binning algorithm excluded any data points flagged suspect and attempted linear interpolation over gaps up to 3 bins wide. If any gaps larger than this were encountered, the data in the gaps were set null.


Project Information

Ocean Margin EXchange (OMEX) I

Introduction

OMEX was a European multidisciplinary oceanographic research project that studied and quantified the exchange processes of carbon and associated elements between the continental shelf of western Europe and the open Atlantic Ocean. The project ran in two phases known as OMEX I (1993-1996) and OMEX II - II (1997-2000), with a bridging phase OMEX II - I (1996-1997). The project was supported by the European Union under the second and third phases of its MArine Science and Technology Programme (MAST) through contracts MAS2-CT93-0069 and MAS3-CT97-0076. It was led by Professor Roland Wollast from Université Libre de Bruxelles, Belgium and involved more than 100 scientists from 10 European countries.

Scientific Objectives

The aim of the Ocean Margin EXchange (OMEX) project was to gain a better understanding of the physical, chemical and biological processes occurring at the ocean margins in order to quantify fluxes of energy and matter (carbon, nutrients and other trace elements) across this boundary. The research culminated in the development of quantitative budgets for the areas studied using an approach based on both field measurements and modeling.

OMEX I (1993-1996)

The first phase of OMEX was divided into sub-projects by discipline:

  • Physics
  • Biogeochemical Cycles
  • Biological Processes
  • Benthic Processes
  • Carbon Cycling and Biogases

This emphasises the multidisciplinary nature of the research.

The project fieldwork focussed on the region of the European Margin adjacent to the Goban Spur (off the coast of Brittany) and the shelf break off Tromsø, Norway. However, there was also data collected off the Iberian Margin and to the west of Ireland. In all a total of 57 research cruises (excluding 295 Continuous Plankton Recorder tows) were involved in the collection of OMEX I data.

Data Availability

Field data collected during OMEX I have been published by BODC as a CD-ROM product, entitled:

  • OMEX I Project Data Set (two discs)

Further descriptions of this product and order forms may be found on the BODC web site.

The data are also held in BODC's databases and subsets may be obtained by request from BODC.


Data Activity or Cruise Information

Cruise

Cruise Name M27_1
Departure Date 1993-12-29
Arrival Date 1994-01-17
Principal Scientist(s)Wolfgang Balzer (University of Bremen, Center for Marine Environmental Sciences)
Ship FS Meteor

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
Q value below limit of quantification