Metadata Report for BODC Series Reference Number 2103670

• 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.

Turner Designs Trilogy Fluorometer

The Trilogy Laboratory Fluorometer is a compact laboratory instrument for making fluorescence, absorbance and turbidity measurements using the appropriate snap-in Application Module.

The following snap-in application modules are available:

For extracted chlorophyll measurements using EPA 445, Trilogy automatically calculates the concentration using the filtered and solvent volumes. The turbidity modules use an IRLED with a wavelength of 860nm to meet ISO 7027 standards for turbidity water quality measurements.

Specifications

Further details can be found in the manufacturer's specification sheet.

AMT22 (JC079) extracted chlorophyll-a measurements from CTD bottle samples

Originator's Protocol for Data Acquisition and Analysis

Samples were taken from 9 CTD rosette bottles to provide a calibration for the fluorometer measurements on each rig. During the cruise 653 samples were collected from 73 CTD casts and processed for extracted chl-a measurements.

At each sampling a 250 ml sample of seawater collected from the non-toxic supply was filtered through a 0.2 µm polycarbonate filter. The chlorophyl-a was then extracted from the filters with 10ml 90% acetone for 24 hours while samples were stored in a freezer. The concentrations were then determined fluorometrically following Welschmeyer (1994).

References Cited

Welschmeyer N.A., 1994. Fluorometric analysis of chlorophyll-a in the presence of chlorophyll-b and phaeopigments. Limnology and Oceanography, 39:1985-1992.

Instrumentation Description

Turner Designs Trilogy fluorometer with a non-acidified chl module (CHL NA #046) fitted

BODC Data Processing Procedures

Data were submitted after the cruise and archived under BODC's accession number BOD120217. The extracted chlorophyll-a data were provided in a file with sample metadata (cruise ID, CTD, station, date, time in UT, latitude and longitude, rosette bottle number and depth). The cruise, CTD number, date, time, latitude and longitude metadata were already loaded to the database from the cruise event log - the metadata combinations in the file matched those in the database. The depth and rosette position metadata were already loaded from the Sea-Bird bottle firing files - the depth and rosette position combinations in the file matched those in the database.

No unit conversion was necessary as the units the data were supplied in the files matched the units for the parameter codes in the BODC Parameter Dictionary.

A parameter mapping table is provided below;

Data Quality Report

There were two samples where the filter was torn during filtration. These values have been flagged as suspect.

These data were updated on 14/05/2014. A cross calibration between AMT cruises 20-23 using the same bench fluorometer revealed a correction factor needed to be applied to the discrete chl-a data for AMT22. Possibly a problem with the standard chl-a solution used for calibration of the bench fluorometer during the cruise. This correction has now been applied to these data. The correction applied was:

Corrected Chl-a = 0.7886 * Chl-a - 0.0012
Copies of these data obtained from BODC before this date will need the correction factor to be applied by the user.

Problem Report

Not relevant to this data set.

CTD Data at bottle firing depths

These data were obtained by BODC software that extracts CTD downcast data (or upcast data if the downcast is unavailable) at depths corresponding to those at which the bottles were fired. The software applies an offset, if present, to the minimum and maximum pressures recorded during bottle firing to account for the distance between the CTD sensor and the mid-point along the bottle. The mean of this depth range is used to find the corresponding CTD data values by interpolation. BODC store these data to enable comparison between CTD and discrete bottle sample data.

Further metadata can be found by searching for the relevant cruise summary report in the BODC cruise inventory. The full CTD profile corresponding to these data is available via the BODC 'all series' application.

Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 1: The Atlantic Meridional Transect (AMT)

The Atlantic Meridional Transect has been operational since 1995 and through the Oceans 2025 programme secures funding for a further five cruises during the period 2007-2012. The AMT programme began in 1995 utilising the passage of the RRS James Clark Ross between the UK and the Falkland Islands southwards in September and northwards in April each year. Prior to Oceans 2025 the AMT programme has completed 18 cruises following this transect in the Atlantic Ocean. This sustained observing system aims to provide basin-scale understanding of the distribution of planktonic communities, their nutrient turnover and biogenic export in the context of hydrographic and biogeochemical provinces of the North and South Atlantic Oceans.

The Atlantic Meridional Transect Programme is an open ocean in situ observing system that will:

• give early warning of any fundamental change in Atlantic ecosystem functionng
• improve forecasts of the future ocean state and associated socio-economic impacts
• provide a "contextual" logistical and scientific infrastructure for independently-funded national and international open ocean biogeochemical and ecological research.

The specific objectives are:

• To collect hydrographic, chemical, ecological and optical data on transects between the UK and the Falkland Islands
• To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems
• To assess the effects of variability in planktonic ecosystems on biogenic export and on air-sea exchange of radiatively active gases

The measurements taken and experiments carried out on the AMT cruises will be closely linked to Themes 2 and 5. The planned cruise track also allows for the AMT data to be used in providing spatial context to the Sustained Observation Activities at the Porcupine Abyssal Plain Ocean Observatory (SO2) and the Western Channel Observatory (SO10).

More detailed information on this Work Package is available at pages 6 - 9 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

Weblink: http://www.oceans2025.org/

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JC079_CTD_CTD67

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: JC079_CTD_CTD67

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

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.