Metadata Report for BODC Series Reference Number 1333381

• 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.

Discrete inorganic nutrient (N, P, Si) samples from CTD bottles during RRS James Cook cruise 32 (JC032)

Originator's Protocol for Data Acquisition and Analysis

Seawater was collected from depth for the analysis of micro-molar concentrations of dissolved inorganic nutrients: nitrate and nitrite (hereafter nitrate), phosphate and silicate. Water was collected from depth using a stainless steel CTD frame fitted with a Sea-Bird SBE 32, twenty-four way carousel (s/n 32-19817-0243) equipped with 20, ten litre OTE external spring water samplers (rosette positions 1-20) and 4, twenty litre OTE external spring water samplers (rosette positions 21-24). All stations occupied during JC032 were sampled for nutrients except stations 22 and 48 (see appendix of the cruise report). Sampling for inorganic nutrients occurred after sampling for chlorofluorocarbons (CFC), dissolved oxygen, argon, carbonate system and salinity. Samples were collected from most CTD bottle depths and spanned the whole water column. Inorganic nutrient concentrations were analysed using a segmented-flow nutrient autoanalyser with colourimetric detection (Skalar SANplus SYSTEM analyser (type 4000) fitted with a Skalar autosampler (type 1000)). The samples were run in analytical triplicates and averaged. The system was calibrated against nitrate (1-40 µmol L^-1), phosphate (0.5-4 µmol L^-1) and silicate (1-120 µmol L^-1) laboratory standards made in artificial seawater (40 g NaCl L^-1) for every run. Efficiency of the cadmium column was checked for each run against a 40 µmol L^-1 nitrite standard. Sample variability of triplicates was <0.8%. The limits of detection were 0.03 µmol L^-1 for phosphate, 0.15 µmol L^-1 for nitrate and 0.2 µmol L^-1 for silicate. More detailed information on the methods used can be found in the cruise report from page 49.

BODC Data Processing Procedures

Inorganic nutrient measurements were provided to BODC in units of µmol kg^-1 and µmol L^-1. Data in µmol kg^-1 were provided in a Comma Separated Values (.csv) file which conformed to the WHP Exchange format. The file contained CTD upcast sensor readings and numerous discrete bottle measurements at bottle firing depths for all CTD casts. Data in µmol L^-1 were provided in MSTAR format NetCDF files, one for each CTD cast. The NetCDF files only contained discrete bottle measurements for nutrients at bottle firing depths. All measurements for nutrients were the average of analytical triplicates. All measurements for nutrients (per kg and per L) were loaded into the BODC database using established BODC data banking procedures. The following changes to the data occurred:

• Absent data: absent data were removed prior to loading.
• Quality control flags: WOCE quality control flags were converted to the corresponding BODC marker.

The data were then loaded to the database without any further changes. The originator's parameters were mapped to appropriate BODC parameter codes as shown below:

Comma Separated Values format file:

MSTAR NetCDF files:

Data Quality Report

A list of data quality and autoanalyser performance observations can be found from page 51 of the cruise report. (Originator's assessment)

Problem Report

None. (BODC assessment)

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JC032_CTD_A09.5/19

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.

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: