Metadata Report for BODC Series Reference Number 910354
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 30-1 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, fluorometer and a rosette sampler equipped with 12 Niskin bottles (12 litre). The CTD unit was mounted vertically in the centre of a protective cage. For the duration of the cruise, the rosette attached to the CTD frame remained inoperative. Calibration data were obtained from bottles lowered on a different rosette directly after the CTD cast.
Data Acquisition
Data were logged at 16 Hz on a PC running EG&G data acquisition software. The channels logged were: pressure, depth, temperature, salinity, sigma-theta, fluorometer volts, oxygen current, oxygen temperature, conductivity and fast temperature (for salinity computation from conductivity).
On-Board Data Processing
The above data channels were converted to ASCII using the EG&G CTDPOST software and supplied to BODC together with the calibration files used.
Post-Cruise Processing
Reformatting
The ASCII data were transferred to 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. This 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 were 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.
The data in ASCII format were then transferred to the BODC internal format (PXF). This allowed the data to be quality assured using in-house software tools, notably the workstation graphics editor.
Editing
Using custom in-house graphics editors, 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 edited or deleted.
Once screened, the CTD downcasts were loaded into the OMEX database under the Oracle relational database management system.
Calibration
With the exception of pressure, calibrations were done by comparison of CTD data against measurements made on water bottle samples and by classical reversing thermometers. As the CTD rosette was inoperative during this cruise, samples were obtained from a separate rosette frame which was lowered directly after the recovery of the CTD frame.
All calibrations described here have been applied to the data.
Pressure
The pressure offset was determined by looking at the pressures recorded when the CTD was clearly logging in air (readily apparent from the conductivity channel). A consistent value was observed throughout the cruise and the following correction has been applied:
| Pcorrected = Pobserved * 0.67 |
Temperature
The CTD temperature calibration of the data as supplied to BODC has been assumed to be correct. Three reversing thermometers were fired in the mixed layer. Two gave ridiculous readings (over 3 °C out). The third was within 0.1 °C of the corresponding CTD reading. The calibration could not, however, be checked in detail because below the mixed layer there is a strong gradient which only has to be displaced slightly by an internal wave to invalidate comparison.
Salinity
The bottle data were compared with the profiles displayed on a graphical workstation. In all cases the water column was stable and the deeper values differed by less than 0.005 PSU. Consequently, it was concluded that calibration of the data as received was good and no further calibration was required.
Chlorophyll
A nominal calibration (slope=4, intercept=-3) has been applied as there are no extracted chlorophyll data available. The calibration was chosen to give a chlorophyll signal in the range 0-5 but it should be emphasised that the result is semi-quantitative at best.
Oxygen
During screening severe hysteresis in oxygen between up and downcast was observed - this exceeded the 'signal' showed by the bottle data set. The fact that the oxygen temperature channel was unusable may well have contributed to the problem. Consequently, the oxygen data have been removed from the data set.
Data Reduction
The final data set was produced by binning the calibrated data to 1 (casts shallower than 100m) 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 gaps were set null.
Data Warnings
Chlorophyll data only have a nominal calibration rendering the data set semi-quantitative at best.
The oxygen data have been deleted from the data set due to the massive hysteresis, in excess of the total signal in the bottle data, between up and downcast data.
Water bottle samples used in the salinity calibration were collected by a separate rosette lowered immediately after the CTD frame was recovered. This creates the potential for calibration errors resulting from changes in the water column structure between casts.
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 | M30_1 |
| Departure Date | 1994-09-06 |
| Arrival Date | 1994-10-11 |
| Principal Scientist(s) | Olaf Pfannkuche (Research Center for Marine Geosciences, Kiel) |
| 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 |
