Metadata Report for BODC Series Reference Number 914841

• 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

Sea-Bird SBE 25 SEALOGGER CTD

The SBE 25 SEALOGGER is a research-quality CTD profiling system used for coastal, estuarine and, can also be a practical option, for deep-water work. It is easily configured in the field for a wide range of auxiliary sensors. The SEALOGGER is self-powered, requires no conductive cable, and is designed for use up to 6800 meters (10,000 psia). It uses the SBE3F temperature and SBE4 conductivity sensors as well as having an external strain gauge pressure sensor. It provides pump-controlled T-C ducted flow, samples at 8 Hz, records internally and provides simultaneous real-time data via its built-in RS-232 interface.

The standard CTD unit comes with a plastic housing (rated to 600 m), although this can be replaced by aluminium housing for depths up to 6800 m.

Specifications

Options and accessories

Additional sensors can be attached to the CTD, including:

• Dissolved Oxygen (SBE 43 DO Sensor)
• pH (SBE 18 pH Sensor or SBE 27 pH/ORP Sensor)
• fluorescence
• radiance (PAR)
• light transmission
• optical backscatter (turbidity)

The SBE 5T titanium pump can be used in place of SBE 5P pump. Further details can be found in the manufacturer's SBE 25 instrument specification.

RV Côte D'Aquitaine NAOMEX2 CTD Data Documentation

Instrumentation and Shipboard Protocols

NAOMEX 2 (BODC mnemonic NAOX2) was a University of Bordeaux cruise on the research vessel Côte d'Acquitaine. The CTD profiles were taken with the SeaBird SBE25 system fitted with a Chelsea Instruments fluorometer, a nephelometer and an oxygen membrane of the Beckman (non-pulsed) type.

Data Acquisition

The SBE25 is normally a self-logging instrument with the data downloaded onto a PC running the SeaBird DATCNV software. The raw data files are converted into ASCII files with the data in oceanographic units on the basis of coefficients held in a calibration file.

Post-Cruise Processing

ASCII DATCNV output files were supplied to BODC.

Reformatting

The data as supplied had been binned to 0.25db with temperature, practical salinity, chlorophyll (nominal units), oxygen (ml/l) and optical backscatter (nominal units).

The data were converted into the BODC internal format (PXF) to allow the use of in-house software tools, notably the workstation graphics editor. In addition to reformatting, the transfer program applied the following modifications to the data:

Dissolved oxygen was converted from ml/l to µM by multiplying the values by 44.66.

The chlorophyll was converted back to a voltage by a natural log transform to conform to the requirements of the BODC CTD data handling system. On retrieval, the data as supplied are reproduced.

Editing and Quality Control

Using custom in-house graphics editors, the limits of the downcast were manually flagged. Any obvious spikes identified were manually flagged 'suspect'.

Once screened, the CTD downcasts (between the flagged limits) were loaded into a database under the Oracle relational database management system.

The salinity data showed none of the problems noted in the data from the previous NAOMEX cruise, indicating that either a different CTD was used or that the instrument had been serviced.

The nephelometer data gave some cause for concern. With the exception of the first cast, CTD07, the data were extremely noisy, with the noise centred on the value returned by CTD07 in clear water. We are convinced that this was an instrument malfunction and have only loaded the data from the one profile into the database.

Calibrations

No sample data were available to calibrate any of the channels. All data are therefore the result of manufacturer's calibrations of unknown date and no guarantee can be given as to the accuracy of the data.

The form of the dissolved oxygen profiles looked perfectly reasonable. However, the absolute values were slightly low with saturations of between 85-95% at the surface. There was also obvious drift from cast to cast. No water bottle oxygen measurements were made on this cruise.

The data from this cruise were collected from a relatively limited area, over a short period of time and the fluorometer data indicate limited phytoplankton activity at the surface. On the basis of this, it was considered justified to 'calibrate' the oxygen data by constraining the surface saturation to the range 99-101%. The following scaling factors were determined and have been applied to the data.

Users should be aware of the possibility that the corrected absolute values will be in error should the assumption that the surface waters were saturated with oxygen prove invalid.

Data Reduction

Once all screening and calibration procedures were completed, the data set was binned to 2 db (casts deeper than 100 db) or 1 db (casts shallower than 100 db). 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.

Downcast values corresponding to the bottle firing depths were incorporated into the database.

Data Warnings

The absolute dissolved oxygen values have been empirically 'calibrated' to enforce saturation at the surface and may be incorrect if this assumption is invalid.

No independent checks, such as reversing thermometer data or salinity bottle data, were available for the verification of the temperature and salinity data. The accuracy of these channels is therefore unknown. Checks against known stable water masses were not possible because there were no casts deeper than 500 m.

The fluorometer has not been calibrated against extracted chlorophyll data. The absolute values may therefore be meaningless.

The nephelometer data are in arbitrary units and their absolute values have no meaning. Only one CTD cast returned sensible nephelometer data.

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: