Metadata Report for BODC Series Reference Number 1350913

• 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

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles and Lever Action bottles have a capacity between 1.7 and 30 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

CD176 Discrete Dissolved Inorganic Nutrients Sampling Document

Originator's Protocol for Data Acquisition and Analysis

Water samples were collected from CTD stations throughout the cruise for the analysis of dissolved inorganic nutrients using an onboard Lachet Quickchem 8000 colorimetric flow injection autoanalyser. Shortly after the cruise started a fault developed with the autosampler, which prevented further onboard analysis. Subsequent samples were collected and filtered through GF/F 0.7 µm filters, before being frozen for analysis back at SAMS.

References Cited

Sherwin, T. A. et al, (2005) 'Cruise CD176 Birkenhead to Falmouth via Rockall, Iceland and Oban', Internal Report No 248, Scottish Association for Marine Science.

Available - Cruise CD176 Internal Report

BODC Data Processing Procedures

The nutrient data were supplied to BODC in Microsoft Excel spreadsheets. Values were extracted from these and loaded into BODC's ocean database under an ORACLE Relational Database Management System. Data that were considered unrealistic were flagged suspect.

Several inconsistencies were noted between the cruise report CTD logsheets and the originator spreadsheets relating to particular Niskin bottles sampled. In all cases the uncertainty involves multiple bottles fired at the same depth, so assignment to bottle numbers was deemed somewhat arbitrary.

Data listed out from the BODC database are done so at a resolution deemed appropriate for that particular variable and the analytical procedure involved. In some instances this results in the listing out of zero values.

SAMS nitrate data quality warning

SAMS have notified BODC of a problem in the analytical procedure adopted for nitrate analysis on this cruise. The problem relates to the technique used to prepare the analytical standards, which results in nitrate (and consequently nitrite) values which are typically 10-15 % higher than they should be. Absolute data values should therefore be used with extreme caution.

Content of data series

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for CD176_CTD_C014

Please note:the supplied parameters may not have been sampled from all the bottle firings described in the table above. Cross-match the Sample Reference Number above against the SAMPRFNM value in the data file to identify the relevant metadata.

Related Data Activity activities are detailed in Appendix 1

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:

Appendix 1: CD176_CTD_C014

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

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