Metadata Report for BODC Series Reference Number 908282
Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
SeaDataNet Quality Flags
Metadata Summary
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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 |
| B | nominal value |
| Q | value below limit of quantification |
