Metadata Report for BODC Series Reference Number 2129027

• 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.

D376 Discrete CTD Inorganic Nutrient Sampling Document

Originator's Protocol for Data Acquisition and Analysis

Sample collection

Triplicate inorganic nutrient samples were drawn from multiple water bottles on 38 of the CTD casts performed on D376. Samples were collected in 60 ml HDPE bottles which were triple rinsed under the flow from each Niskin bottle prior to being filled to 80 % capacity. The bottles were immediately capped and taken to the onboard chemistry laboratory for analysis within two hours.

Sample analysis

A Bran and Luebbe QuAAtro 5-Channel Nutrient Auto-analyser was used for the determination of nutrient concentrations.

Analytical standards were prepared onboard using high purity salts. Check standards, using commercially available nutrient standards, were also prepared. Standards were prepared in artificial seawater (consisting of 35 g sodium chloride and 0.5 g sodium bicarbonate dissolved in 1 litre of Milli-Q water). During analysis, baseline and drift corrections were applied to ensure analytical integrity. The precision for all nutrients was in excess of 1 %.

Nitrate+Nitrite

A copperised cadmium reduction coil was used to reduce nitrate to nitrite at pH 8. This nitrite (from nitrate), together with nitrite already present in the sample, was then reacted with sulphanilamide and N-(1-naphthyl)-ethylenediamine dihydrochloride (NEDD) to produce a red-purple azo dye, which was measured colorimetrically.

The analytical detection limit for nitrate+nitrite was 0.1 µmol/l.

Nitrite

The nitrite present in each sample was determined in the same manner as above, but without using the copperised cadmium column.

The analytical detection limit for nitrite was 0.05 µmol/l.

Phosphate

Phosphate concentration was determined by reaction of phosphate in the sample with molybdate and antimony ions and subsequent reduction with ascorbic acid to produce a phospho-molybdenum complex which was measured colorimetrically

The analytical detection limit for phosphate was 0.05 µmol/l.

Silicate

Silicate concentration was established colorimetrically by reducing a silico-molybdate complex in acid solution to a molybdenum blue complex using ascorbic acid. The addition of oxalic acid ensured any interference from phosphate was minimal.

The analytical detection limit for silicate was 0.1 µmol/l.

Ammonium

Ammonium concentrations were determined by reaction with o-phthalaldehyde (OPA) at 75 °C in the presence of a borate buffer. The addition of sodium sulphite resulted in the production of a fluorescent species in proportion to the ammonium concentration present. This was measured fluorimetrically using a JASCO FP-2020 Intelligent fluorescence detector.

The analytical detection limit for ammonium was 0.05 µmol/l.

BODC Data Processing Procedures

A MS Excel spreadsheet containing biogeochemistry data was supplied to BODC by the data originator, Claire Mahaffey (University of Liverpool). Mean values of the triplicate nutrient analyses were provided alongside standard deviations and coefficients of variation (CV) for each value. Quality control markers were also included.

The mean values (together with associated standard deviations) were loaded to BODC's ocean database under the ORACLE Relational Database Management System. Originator flags, where present, were also mapped across (to BODC 'L' flags). There were some occurrences where derived nitrate values had been flagged by the originator. BODC have assigned corresponding 'M' flags to the associated nitrate+nitrite and nitrite values in these instances as calculation of nitrate is intrinsically linked to these other variables.

The CV values were not ingested into the database as these are derived measurements which can easily be reproduced (standard deviation divided by mean value).

Content of data series

References

Inall, M. E. et al.,(2012). 'Cruise D376 Swansea to Southampton FASTNEt Cruise to the Celtic Sea Shelf Edge'. Internal Report No 277, Scottish Association for Marine Science.

Project Information

Fluxes Across Sloping Topography of the North East Atlantic (FASTNEt)

Background

The FASTNEt consortium was funded to deliver NERC's Ocean Shelf Edge Exchange Programme. Commencing in October 2011, this four year study aims to couple established observational techniques, such as moorings and CTDs, with the very latest in autonomous sampling initiatives - including use of Autosub Long Range and gliders. With the aid of novel model techniques, these observations will be utilised to construct a new paradigm of Ocean/Shelf exchange.

Shelf edge regions mark the gateway between the world's deep oceans and shallower coastal seas, linking terrestrial, atmospheric and oceanic carbon pools and influencing biogeochemical fluxes. Shelf edge processes can influence near-shore productivity (and fisheries) and ultimately affect global climate.

FASTNEt brings together researchers from multiple UK organisations. Further collaboration has been established with five Project Partners: the UK Met Office, Marine Scotland Science, Agri-Food and Biosciences Institute, Marine Institute Ireland and Scripps Institution of Oceanography.

Scientific Objectives

• To determine the seasonality of physical gradients and exchange across the shelf edge by deploying new observational technologies (gliders, Autosub Long Range) and established techniques (long term moorings, drifters)
• To quantify key exchange mechanisms and to collect new data targeted at testing and improving high resolution models of the shelf edge, by carrying out detailed process studies in contrasting regions of the shelf edge of the NE Atlantic margin
• To develop a new parameterisation of shelf edge exchange processes suitable for regional-scale models, using improved resolution numerical, and new empirical models constrained by the observations
• To test the new parameterisations in a regional model in the context of making an assessment of inter-annual variability of ocean-shelf exchange.

Fieldwork

Three survey sites on the UK shelf edge have been selected for FASTNEt. These are a) the Celtic Sea shelf edge, b) Malin shelf and c) North Scotland shelf. Fieldwork is centred around two research cruises. The first, to the Celtic Sea, on RRS Discovery in June 2012. The second cruise visits the Malin shelf on RRS James Cook, during summer 2013. In addition to these dedicated cruises, opportunist cruise activity to the North Scotland shelf has been agreed with project partner Marine Scotland Science. Autonomous technologies will complement observations made during the cruises and provide knowledge of seasonal and inter-annual variability in exchange processes.

Instrumentation

Types of instruments/measurements:

• Gliders
• Autosub Long Range
• Drifter buoys
• Scanfish
• Microstructure profilers
• Moored CTD/CT loggers and ADCPs
• Shipboard measurements: CTD, underway, nutrients (and other discrete sampling), LADCP, ADCP.

Contacts

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for D376_CTD_C017

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

Fixed Station Information

FASTNEt CTD Station A12

Station A12 was a CTD Station which was occupied repeatedly during FASTNEt cruise D376.

In total 12 casts were performed between 18/06/2012 and 19/06/2012, with the CTD package returning briefly to deck between casts in order for the ship to reposition.

The nominal position of Station A12 was 49.2° N, 8.5° W.

Related Fixed Station activities are detailed in Appendix 1

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: FASTNEt CTD Station A12

Related series for this Fixed Station 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.