Metadata Report for BODC Series Reference Number 2281576

• 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.

Dissolved Oxygen 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, CH123B, CH125B, CH126B and CH128A

Samples for oxygen analysis were collected from Niskin bottles on the CTD rosette using a length of silicone tube into calibrated, ground-glass stoppered borosilicate bottles. The bottles were rinsed three times and sample water was allowed to oveflow for a short time to ensure that it was free from air bubbles.

Manganous sulphate and alkaline sodium iodide solutions were added to the seawater sample and the bottle was stoppered and shaken. The oxygen in the seawater oxidised some of the hydroxide to a tetravalent manganese compound. The quantity of this was determined by making the solution acid and titrating the liberated iodine with sodium thiosulphate, using potentiometric end-point detection. The protocol followed the enhanced techniques described in Bryan et al. (1976) and used a micro-burette, which enabled high precision in the titration.

The bottles were prepared as follows. After acid-washing and drying, each bottle was allocated a number and a matching stopper and weighed on an Oertling OB33 balance. The bottles were weighed dry twice, with an agreement of 3mg, and the average weight calculated. The bottles were then filled with tap water, capped with ground glass stoppers, carefully dried and weighed. The average wet weight for each bottle was calculated once weight replicates were less than 10 mg for full bottles. The average of those two weights was then calculated. The difference between average dry and average wet weight was then calculated to give the volume of each bottle in ml.

The thiosulphate was standardised against a standard solution of potassium iodate.

BODE processing

The data values present in the bottle database have been obtained by BODC software, which extracts CTD downcast data corresponding to the bottle firing depths. This ensures an internally consistent data set across all cruises regardless of whether or not the upcast data were made available. The method is prone to errors if significant changes occur to water column structure during the cast.

The calibration and data processing protocols for the dissolved oxygen data were complex and varied from cruise to cruise. Further details are given in the CTD data documentation and users are strongly recommended to consult this before using the CTD-derived data.

The oxygen saturation values have been computed from calibrated temperature and salinity data using the algorithm of Benson and Krause (1984).

Comments on data quality

In most cases, the calibrated CTD oxygen data are in good agreement with the water bottle data. It should be noted that bottle measurements were only made on a small proportion of the casts but the resulting calibration has been applied to all casts from the cruise.

However, this is not the case for cruise CD93B where the CTD oxygen values are some 10-20% higher than the bottle values. The problem has been investigated but no processing errors could be identified. It is therefore recommended that the CTD-derived data from this cruise be used with extreme caution.

References

Benson B.B. and Krause D. jnr. 1984. The concentration and isotopic fractionation of oxygen dissolved in fresh water and sea water in equilibrium with the atmosphere. Limnol. Oceanogr. 29, pp.620-632.

Bryan J.R., Riley J.P. and Williams, P.J.LeB. 1976. A Winkler procedure for making precise measurements of oxygen concentration for productivity and related studies. Journal of Experimental Marine Biology and Ecology, 21, 191-197.

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 CH123B_CTD_CTD53

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: CH123B_CTD_CTD53

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.