Metadata Report for BODC Series Reference Number 953065

• 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

CH42 Sea surface Hydrography Data Quality Report

The non-toxic supply pump was inoperative from 20.35 to 21.45 on 19 December.

Thermosalinograph

The thermosalinograph performed well throughout the cruise except for a logging problem which caused variable degrees of data loss on 16 and 17 December.

Transmissometer

The transmissometer performed well with little evidence of bubble spikes. Periods of data have been flagged out where the instrument was saturated by extremely turbid waters.

Chlorophyll

All chlorophyll data after 14.15 on 27 December have been flagged out.

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

Technicon AutoAnalyzer II (AAII)

The AAII is a segmented flow analyzer used for automated colorimetric analysis. The apparatus uses 2 mm diameter glass tubing and pumps reagents at flow rates of 2 to 3 ml s^-1, producing results at a typical rate of 30 to 60 samples per hour. The system comprises an autosampler, peristaltic pump, chemistry manifold a detector and a data acquisition software.

This instrument was replaced by the AA3 in 1997 which was upgraded to the AA3 HR systems in 2006.

Specifications

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

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

Decca Navigator System

The Decca Navigator System (DNS) was a hyperbolic radio navigation system that operated by measuring the phase differences between continuous signals from master and slave stations. The differences were then related to hyperbolic lines printed on a chart (also known as lines of lattice). By plotting the readings from two pairs of hyperbolas at any particular instant, the user was able to plot their position instantly. The system operated from WWII until the UK transmitters were switched off at the end of March 2000.

The DNS consisted of groups of at least three shore based transmitter stations (or chains) which comprised one Master and two or three slave stations, usually located 80 to 110 km from the master station and positioned about 120° apart. The accuracy of this system depended on the distance to the baseline, time of day and seasonal effects.

The table below presents the general specifications for this system.

Specifications

Further details can be found here.

SeaTech Transmissometer

Introduction

The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.

Specifications

• Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
• Beam diameter: 15 mm
• Transmitted beam collimation: <3 milliradians
• Receiver acceptance angle (in water): <18 milliradians
• Light source wavelength: usually (but not exclusively) 660 nm (red light)

Notes

The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.

A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.

Further details can be found in the manufacturer's Manual.

CH42 Sea surface hydrography instrument details

Underway hydrography was recorded by a suite of instruments in the ship's flow-through system. Instrument details are given in the table below.

CH42 Sea surface Hydrography Series Processing Notes

Nutrients

Nutrient values were determined using a Technicon AA2 autoanalyser connected to the general non-toxic seawater supply via a continuous filtration block (Morris et al., 1978).

The chemistries used were:

In all cases the colorimeter output was as a voltage to a chart recorder which was tapped off and logged automatically at 1 minute intervals.

Calibration was achieved by running four standard concentrations through the system once or twice a day. Distilled water washes were passed through the system at approximately six-hourly intervals.

The data were subdivided into segments using the analyst's notes and the chart records for which the basline was linear and a single calibration curve applied.

The processing system computed a baseline drift equation for each segment and, in a second pass, stripped off the baseline. Calibration equations were computed and applied to each segment. The calibration program additionally converted all baseline and standard flags to suspect.

Silicate required an additional processing step prior to baseline correction. Running a distilled water wash caused the silicate signal voltage to drop, sometimes by as much as 100 per cent. This voltage drop was assumed to be a linear drift between baselines and corrected on this basis.

Post-processing quality control comprised checking time series plots for any spikes which have been overlooked and checking the concentrations computed for the standards.

The internal processes of an autoanalyser involve considerable delays between the collection of a water sample and the logging of the data point for that sample. Time corrections were applied to synchronise nitrate to salinity and the other three nutrients to nitrate.

Chlorophyll

Chlorophyll concentrations were measured using an Aquatracka logarithmic response fluorometer mounted in a light-tight box on the starboard deck.

The fluorometer was calibrated by regressing the natural log of chlorophyll concentration against fluorometer voltage. No chlorophyll samples were taken on this cruise, so the fluorometer was 'calibrated' using data from Challenger 39. Chlorophyll concentrations were thus computed using the equation:

Chlorophyll (mg m^-3) = exp(1.1560 * fluorometer voltage - 2.0970)

Sea surface temperature and salinity

Temperature and salinity were measured using an autoranging TSG103 thermosalinograph. Temperature was measured by a thermistor in the non-toxic supply inlet manifold. Conductivity was measured by a unit in the ship's wet laboratory, which included a second thermistor to provide temperature for the computation of salinity.

The thermosalinograph was intercalibrated against surface values taken from the calibrated CTD. The corrections applied to the thermosalinograph and the time period for which they are valid are shown below:

Optical Attenuance and Sediment Load

Optical transmittance was measured using a SeaTech red light (661nm) transmissometer with a 25cm optical path length mounted in a light-tight box on the starboard deck.

Transmissometer air readings recorded during the cruise were used to correct the transmissometer voltage to the manufacturer's specified voltage by ratio. The voltages were then converted to attenuance to eliminate the influence of instrument path length using the equation:

Attenuance = -4.0 * log_e (voltage/5.0)

Attenuance was regressed against total suspended matter determinations to derive the equation below to allow attenuance to be expressed as suspended matter:

SPM (mg/l) = (Attenuance - 1.0800) / 0.4600 (n=49)

Dissolved Oxygen

Dissolved oxygen was measured using an Endico type 1125 pulsed dissolved oxygen controller multiplexed with two Endico type 1128 dissolved oxygen probes. The probes were immersed in a perspex cell (approx. 1 litre volume) supplied from the general non-toxic supply via a constant head device at 2 litres/minute.

The dissolved oxygen data were corrected for temperature but as the software was unable to cope with salinity variation were computed at zero salinity. At regular intervals triplicate samples were drawn off from the probe outflow into 60 ml borosilicate glass stoppered bottles and analysed for oxygen by Winkler titration.

These values, recomputed to zero salinity, were used to select the most accurately responding of the two electrodes and then calibrate it by linear regression. Once calibrated, the data were recomputed to in-situ salinity using the equations:

O₂ (actual) = O₂ (zero salinity) / Gamma

Gamma = exp (S*(A6 + A7/T + A8/T**2))

where: S = Salinity (PSU) T = Absolute temperature (K) A6 = 0.017674 A7 = -10.754 A8 = 2140.7

Oxygen saturation was computed using the equation of Weiss (1970).

Photosynthetically Active Radiation

The PAR meters were calibrated using the following laboratory determined calibrations:

References

Fofonoff, N.P. and Millard Jr., R.C. (1983). Algorithms for computation of fundamental properties of seawater. UNESCO Technical Papers in Marine Science 44.

Morris, A.W., Howland, R.J.M., and Bale, A.J. (1978). A filtration unit for use with continuous autoanalytical systems applied to highly turbid waters. Est. Coast. Mar. Sci. 6, 105-109.

Weiss, R.F. (1970). The solubility of nitrogen, oxygen and argon in water and sea water. Deep Sea Research 17, 721-735.

CH42 Sea surface Hydrography, Meteorology and Navigation Series

Instrumentation

A suite of parameters were logged from the non-toxic supply, the intake for which was located on the ship's hull, about 2m below the surface.

Operational procedure and data logging

Data were logged by the Research Vessels Services ABC data logging system. The data output units were sampled every 30 seconds by a microprocessor interface (the Level A) which passed time stamped data cycles to a Sun workstation (the Level C) via a buffering system (the Level B). Navigation was updated every two minutes and infilled by linear interpolation. Dissolved oxygen and probe temperature were logged at 15 minute intervals by a PC connected to the Endico controller and transferred to the Level C on floppy disk.

Data Processing

The raw data comprised ADC counts. These were converted into engineering units (degrees for latitude/longitude, volts for PAR meters, fluorometer, transmissometer and nutrients, mmho/cm for conductivity, degC for temperature, metres for bathymetry) by the application of laboratory determined calibrations and salinity was calculated using the algorithm in Fofonoff and Millard (1983). The data were submitted to BODC in this form.

References

Fofonoff, N.P. and Millard, R.C. Jr. (1983). Algorithms for the computation of fundamental properties of sea water. UNESCO Technical Papers in Marine Science 44.

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

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: