Metadata Report for BODC Series Reference Number 1865272

• 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.

CTD Calibration Sample Data Set as part of the North Sea Project

Document History

Converted from CDROM documentation.

Sampling strategy and methodology

During the North Sea Project a significant data set of samples used to calibrate the CTD sensors accrued. This document describes the methods used to obtain these data.

Salinity

A salinity sample, usually from the bottle fired nearest to the sea floor, was drawn from each cast after several washings with the sample sea water into a screw topped glass bottle with an airtight plastic seal. Samples were transferred in batches to the ship's constant temperature laboratory where they were left for at least 24 hours to attain thermal equilibrium.

Salinities were measured on a Guildline Autosal salinometer using standard sea water as a reference standard. Occasionally, if supplies of standard sea water ran low, batches of sea water calibrated against standard sea water were used as a secondary standard.

Quality control comprised the rejection of salinity values shown to be erroneous during the CTD calibration exercise.

Temperature

On each CTD cast one of the sample bottles (usually the first to be fired at the bottom of the cast) was fitted with a frame containing two SIS RTM-4002 digital thermometers which reversed, triggering the thermometers, when the bottle was fired.

The readings were corrected using manufacturers calibration sheets. If the calibrated values differed by more than 0.009C, the data were checked and erroneous values rejected. Checks were also made to eliminate erroneous data resulting from failure to reset the thermometers between casts. The two values (if both deemed good) were averaged. Any further values shown to be erroneous during the CTD calibration exercise were deleted from the data set.

Dissolved Oxygen

Three replicate samples were drawn from the water bottles into 60 ml borosilicate glass stoppered bottles and 0.5ml of each Winkler reagent added using BCD multi-addition pipettes. The reagents were prepared according to the recommendations of Carrit and Carpenter (1966). After mixing, the oxygen bottles were stored under fresh water until analysed.

Analysis was undertaken on board using the manual photometric endpoint detector method described by Bryan et al (1976).

Chlorophyll and Phaeopigment

Extracted chlorophyll and phaeopigments for all cruises where chlorophylls were done with the exception of CH72A and CH72C were determined in the same laboratory, Plymouth Marine Laboratory, using the following protocol.

Up to 2 litres of water for each sample were filtered through glass fibre filters (GFF) and frozen quickly on board ship. The samples were returned frozen to the laboratory where they were extracted with 90% acetone and assayed in a scanning spectrophotometer. The concentrations of chlorophyll and phaeopigments were calculated using the SCOR-UNESCO algorithms (Strickland and Parsons, 1968).

The chlorophyll and phaeopigment determinations on the two legs of Challenger 72 (A and C) in 1990 were undertaken by a different group using a totally different protocol as follows.

Up to 0.5 litres of sea water were filtered through Whatman GFF filters taking care to avoid unnecessary exposure to light. Filters were then extracted, on board ship, in the dark in 90% Analar grade acetone, 10% distilled water, neutralised with sodium bicarbonate.

Fluorescence was measured at sea using a Turner Designs bench fluorometer, calibrated using spectrophotometrically determined standards, before and after acidification with 8% HCl. Chlorophyll and phaeopigment concentrations were calculated using the equation in Tett (1987). The resulting measurement of 'chlorophyll' is the sum of chlorophyll-a and chlorophyllide-a.

Total and Organic Sediment

Two litres of water were drawn from each CTD bottle into a large measuring cylinder. Each sample was filtered using a vacuum filtration system onto a pre-weighed filter. On the early cruises (CH28, CH33, CH35, CH37 and CH39) Nucleopore filters were used. On later cruises these were replaced by GFF filters. Each sample was carefully washed with distilled water to remove salt, removed from the filtration system and air dried.

In some cases where samples had a large sediment load it proved impossible to filter two litres. In these cases, as much of the sample as possible was filtered and the volume filtered determined by noting the volume of water remaining in the measuring cylinder.

After the cruise, each sample was dried and reweighed to constant weight to give the total suspended matter concentration. The samples were then ashed and the organic sediment content obtained from the loss of weight on ignition. The polycarbonate Nucleopore filters used at the beginning of the project decomposed on ignition. Consequently, there are no organic sediment data for project cruises before Challenger 41.

References

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. J. Exp. Mar. Biol. Ecol. 21, 191-197.

Carrit, D.E. and Carpenter, J.H. (1966). Comparison and evaluation of currently employed modifications of the Winkler method for determining dissolved oxygen in sea water. J. Mar. Res. 24, 286-318.

Strickland, J.D.H. and Parsons, T.R. (1968). A practical handbook of sea water analysis. Bull.Fish.Res.Bd.Can.:167.

Tett, P.B. (1987). Plankton: in Baker, J.M. and Wolff, W.J. (eds.) Biological surveys of estuaries and coasts. CUP, Cambridge, U.K. 280-341.

Project Information

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

• Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;
• Identifying and quantifying non-conservative processes - sources and sinks determining the cycling and fate of individual constituents;
• Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for CH57_CTD_2494

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

North Sea Project Survey Mooring Site A and CTD Site CS

Site A was one of six fixed stations where moorings were deployed during the North Sea Project survey. This location is also one of 123 North Sea Project CTD Sites.

The site was characterised by weak tidal currents, up to a maximum of 0.5 m/s, and the water column was stratified in summer months.

The rigs deployed here lie within a box bounded by co-ordinates 55.493N 0.893E at the southwest corner and 55.563N 0.920E at the northeast corner. Magnetic variation at this site was 4.5° west.

Site A deployment history is summarised below:

ADCP = Acoustic Doppler Current Profiler
CM = Current Meter (Aanderaa or S4)
THCH = Thermistor Chain
FL = Fluorometer

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: CH57_CTD_2494

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: NSP Survey A and CTD Site CS

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.