Metadata Report for BODC Series Reference Number 907764

• 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

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.

Further details can be found in the specification sheet.

RV Jan Mayen 4 CTD Data Documentation

Instrumentation

The CTD profiles were taken with a Neil Brown Mk3 CTD incorporating a pressure sensor, conductivity cell and platinum resistance thermometer. An in-situ fluorometer and a rosette fitted with 5 litre Niskin bottles were included in the package.

The CTD was a relatively new instrument and the manufacturer's temperature and conductivity calibrations were used.

Data Acquisition and Originator Processing

Data were logged at 16 Hz on a PC running EG&G data acquisition software and subsequently incorporated into the Tromsø data system. Data were delivered to BODC binned to 1 metre with the channels temperature, salinity and nominal chlorophyll.

Post-Cruise Processing

Reformatting

The data supplied were transferred to the BODC internal format (PXF). The translation program also converted depths to pressures using an inverse of the standard UNESCO algorithm and applied a natural log transform to the nominal chlorophyll data to make them compatible with BODC's CTD processing system.

Editing

Using a custom in-house graphics editor, the downcasts were delimited by manually applying flags to the cycle number channel. In addition, any dubious data (such as equilibration artefacts at the surface) or spikes in the downcast channels were manually flagged suspect. Temperature and salinity were noted as being unusually noisy.

Once screened, the CTD downcasts were loaded into the OMEX database under the Oracle relational database management system.

Calibration

The data were supplied to BODC calibrated and no further modifications have been made to the temperature and salinity data. The originator's calibration was as supplied by the manufacturer and, as this was a relatively new instrument when used on this cruise, is believed by the originator to be reliable.

The fluorometer was calibrated against fluorometrically assayed extracted chlorophyll data and the following relationship obtained:

This has been applied to the data held in the database. Note that near-surface data points affected by quenching were excluded from the calibration.

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.

Data Warnings

The temperature and salinity data were unusually noisy.

The fluorometer data exhibited clear examples of 'quenching' where photo-adaptive reactions of the phytoplankton caused a variation in fluorescence yield as a function of depth near the surface. Consequently, calibrated fluorometer values in the top 10-15 m should be regarded as possible underestimates of the true chlorophyll concentration.

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

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: