Metadata Report for BODC Series Reference Number 2262702

• 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

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.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

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.

Particulate Organic Carbon and Nitrogen for Charles Darwin and RRS Challenger cruises

Document History

Converted from CDROM documentation.

Content of data series

Data Originator

Dr Paul Tett, University of Wales, Bangor, UK.

Sampling strategy and methodology

Charles Darwin cruises CD93A and CD93B and RRS Challenger cruises CH121B, CH121C, CH123A, CH123B, CH125A, CH125B, CH126A, CH128A and CH128B.

Water samples were collected using Niskin bottles deployed on a CTD rosette and filtered through 25 mm GF/F filters. On most cruises, two aliquots were filtered to provide samples for the determination of particulate total carbon and particulate organic carbon. Note that this procedure resulted in duplicate determinations of total particulate nitrogen. The nitrogen data stored in the database are exclusively from the POC samples to prevent sample heterogeneity distorting organic C/N ratios. The samples were stored frozen until analysed.

The thawed filters were dried at 60C overnight in an oven, inside a pre-cleaned open plastic dish. The POC samples were placed into a pre-cleaned hermetic plastic container inside a pre-cleaned open plastic dish. Using an excess quantity of Analar concentrated HCl in a 50 ml beaker, the samples were exposed directly to HCl vapour for 30-48 h at room temperature. This acidification procedure removed inorganic carbon present as carbonate. The samples were removed and heated in an oven for 1 h at 60C to drive off residual HCl and water before they were analysed. Untreated and acidified samples were handled separately to avoid residual acid vapours in the HCl-treated samples reacting with carbonates in untreated samples.

Each TPC and POC sample was folded carefully into a rectangular shape, using sterilised forceps, inside a 30x30 mm square pre-cleaned tin foil. This maximised the oxidation reaction in the combustion chamber and allowed the sample to pass through the CHN analyser oxidation furnace entrance.

The carbon and nitrogen analyses were carried out at Dunstaffnage Marine Laboratory using a LECO CHN-900 Elemental Analyser with helium as the carrier gas and pure oxygen for combustion. Simultaneous determination of the carbon and nitrogen content of the samples was achieved by measuring the products of combustion using non-dispersive infrared detection and thermal conductivity.

The CHN analyser was calibrated using a known weight of a suitable standard organic compound having a known carbon and nitrogen content: acetanilide (CH₃CONHC₆H₅) containing 71.09% of carbon and 10.36% of nitrogen. Between 1995 and 1997 five visits were made to DML to analyse the samples. To avoid any errors resulting from changes in instrument settings, a separate calibration was made on each visit. Each calibration involved analyses of standards on each day of use to check for calibration drift during a visit. Four empty tin foils were analysed on each calibration run as blanks.

The units of the data were converted from mg/m³ to µM at BODC by dividing the carbon values by 12.011 and the nitrogen values by 14.007.

Comments on data quality

The data were examined at BODC and a number of obviously anomalous values were flagged suspect, including one complete profile that appeared to be inverted.

The unacidified carbon values exceeded the acidified values for a significant number of samples. The two carbon determinations were done on separate filtrations and consequently small negative differences are to be expected due to sample heterogeneity. However, in some cases the acidified carbon values were up to 10µM greater.

In these cases, if one of the two values was clearly anomalous then it was flagged. However, users should be aware that in some cases it was impossible to ascertain which of the two values was in error and no flags were applied.

Project Information

LOIS Shelf Edge Study (LOIS - SES)

Introduction

SES was a component of the NERC Land Ocean Interaction Study (LOIS) Community Research Programme that made intensive measurements from the shelf break in the region known as the Hebridean Slope from March 1995 to September 1996.

Scientific Rationale

SES was devoted to the study of interactions between the shelf seas and the open ocean. The specific objectives of the project were:

• To identify the time and space scales of ocean-shelf momentum transmission and to quantify the contributions to ocean-shelf water exchange by physical processes.

• To estimate fluxes of water, heat and certain dissolved and suspended constituents across a section of the shelf edge with special emphasis on net carbon export from, and nutrient import to, the shelf.

• To incorporate process understanding into models and test these models by comparison with observations and provide a basis for estimation of fluxes integrated over time and the length of the shelf.

Fieldwork

The SES fieldwork was focussed on a box enclosing two sections across the shelf break at 56.4-56.5 °N and 56.6-56.7 °N. Moored instrument arrays were maintained throughout the experiment at stations with water depths ranging from 140 m to 1500 m, although there were heavy losses due to the intensive fishing activity in the area. The moorings included meteorological buoys, current meters, transmissometers, fluorometers, nutrient analysers (but these never returned any usable data), thermistor chains, colour sensors and sediment traps.

The moorings were serviced by research cruises at approximately three-monthly intervals. In addition to the mooring work this cruises undertook intensive CTD, water bottle and benthic surveys with cruise durations of up to 6 weeks (3 legs of approximately 2 weeks each).

Moored instrument activities associated with SES comprised current measurements in the North Channel in 1993 and the Tiree Passage from 1995-1996. These provided boundary conditions for SES modelling activities.

Additional data were provided through cruises undertaken by the Defence Evaluation and Research Agency (DERA) in a co-operative programme known as SESAME.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for CH126A_CTD_CP18

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

Fixed Station Information

LOIS (SES) Repeat Section P

Section P was one of four repeat sections sampled during the Land-Ocean Interaction Study (LOIS) Shelf Edge Study (SES) project between March 1995 and September 1996.

The CTD measurements collected at repeat section P, on the Hebridean Slope, lie within a box bounded by co-ordinates 56° 33.0' N, 9° 37.8' W at the southwest corner and 56° 39.0' N, 8° 55.8' W at the northeast corner.

Cruises occupying section P

Related Fixed Station activities are detailed in Appendix 2

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: CH126A_CTD_CP18

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.

Appendix 2: LOIS (SES) Repeat Section P

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.