Metadata Report for BODC Series Reference Number 1222799

• 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

RRS James Clark Ross AMT2 (JR13) Underway Hydrographic Data Quality Report

Further to the processing documentation there are no additional known data quality issues.

Data Access Policy

Public domain 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.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

Turner Designs 10AU Field Fluorometer

The Turner Designs 10AU is designed for continuous-flow monitoring or discrete sample analyses of fluorescent species. A variety of optical kits with appropriate filters and lamps are available for a wide range of applications. Individual filters and lamps are also available for customised applications.

Standard optical kits include those for chlorophyll-a (extracted and/or in vivo), phycocyanin, phycoerythrin, CDOM, ammonium, rhodamine and fluorescein dye tracing, crude oil, refined oil, histamine and optical brighteners.

The instrument's light source is a 4 watt lamp and the detector is a photomultiplier tube with a standard detection range of 300-650 nm. A red-sensitive version with a detetion range of 185-970 nm is also available.

Specifications

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

Trimble 4000DS Global Positioning System receiver

The Trimble 4000DS Differential Surveyor is similar to the 4000RS (a Maxwell-based receiver that is oriented toward precision positioning applications. It is intended for use as a DGPS base station, generating RTCM-104 corrections). The 4000Ds can apply RTCM-104 corrections to the satellite data it receives in order to generate accurate position fixes in real time.

RRS James Clark Ross AMT2 (JR13) Underway Hydrographic Instrumentation

The instrumentation has been collated from various sources as historic notation of instrumentation was not well maintained. Care may be required if making assumptions based on the instruments used.

The following instruments were used for hydrographic measurements:

RRS James Clark Ross AMT2 (JR13) Underway Hydrographic Data Processing Procedures

Originator's Data Processing

Raw data were logged as ADC counts on the ship's computers. They were converted into engineering units using initial manufacturers' calibrations. Conductivity and two temperature channels were produced from the thermosalinograph counts using laboratory calibrations on board ship.

The data from the fluorometer was logged into the JCR Ocean Logger system using the internal A/D converter and range output. The fluorometer had an autoranging capability which maximises the sensitivity of the instrument in areas of different chlorophyll concentrations.

The data were submitted to BODC in RVS internal format for post-cruise processing and data banking.

BODC Data Processing

Reformatting

Underway data files were merged into a single binary merge file using time as the primary linking key. The time span of the file was from 22/04/1996 12:10:00 to 22/05/1996 07:17:30, with a sampling interval of 30 seconds.

Salinity was computed from housing temperature and conductivity using the UNESCO 1978 Practical Salinity Scale (Fofonoff and Millard, 1982).

Screening

Each data channel was inspected on a graphics workstation and any spikes or periods of dubious data were flagged. The power of the workstation software was used to carry out comparative screening checks between channels by overlaying data channels. A map of the cruise track was simultaneously displayed in order to take account of the oceanographic context.

Data processing, correction and calibration

Sample Calibrations

Temperature

Temperature and salinity readings from the thermosalinograph were compared with precision reversing thermometers mounted on the CTD frame at the 7 m position. The calibration exercise was carried out by Tony Bale (PML), and the results are presented in the AMT2 cruise report. The station at which each comparison was made is provided, but it is not known whether it was carried out during the first or second CTD cast on station, so the data are not present in the database. However, they are presented in the table below.

The mean and standard deviation of the offsets, for all samples, are 0.0776 and 0.1538 respectively. If the outlying values are removed (those shown in bold), the mean and standard deviation is 0.0282 and 0.0398.

The underway sea temperature channel was also compared with averaged surface values extracted from CTD profiles to 7 metres. The 49 samples gave a small offset of -0.00143 °C between CTD and surface underway data with a standard deviation 0.0310. However, the calibration sample data were derived from averaging several data points; some of these showed a high degree of variability in the underway or CTD data at the time of the calibration point (having a standard deviation of 0.02 °C or greater). When these samples were removed from the data set, the mean offset was 0.000511 °C, with a standard deviation of 0.02366 (N=45). Due to the low offset and relatively high standard deviation of the calibration samples, no correction was required for the original temperature channel.

Salinity

Salinity values from the thermosalinograph were compared with the salinity of samples taken from the non-toxic supply measured on the Autolab precision salinometer. The calibration exercise was carried out by Tony Bale (PML).

The data are presented in the table below (taken from the AMT2 cruise report).

The mean and standard deviation of the offset values are 0.01 and 0.03 respectively.

Surface CTD data were also extracted to calibrate the underway salinity. The offset was -0.00293 PSU, with a standard deviation of 0.00996 (N=44). The low offset indicated that the salinity channel required no correction to be applied to the data.

Fluorescence

As the data logged from the fluorometer did not contain corrections for range changes, the exact time and scale of each range change was noted during the screening process at BODC. The data were then adjusted to the same range throughout the cruise, using the correction fluorc = fluor*(31.6/range).

After corrections were made for the range changes, the data were compared with fluorometric chlorophyll-a concentrations measured on samples taken from the non-toxic supply. The resulting relationship was used to calibrate the underway fluorometer.

     Calibrated chlorophyll-a (mg m-3) = 0.00263 * fluorometer value - 0.0534     (n=255, R2=73.3%)

The effect of quenching was assessed by adding PAR into a multiple regression. There was no improvement in the fit, so no correction for quenching was made.

References

Fofonoff, N.P. and Millard Jr., R.C., 1982. Algorithms for Computation of Fundamental Properties of Seawater. UNESCO Technical Papers in Marine Science, 44.

SeaBird 21 SeaCAT Thermosalinograph SBE 21

The SBE21 is an externally powered instrument used to determine sea surface temperature and conductivity from underway vessels. Data is simultaneously stored in memory and output to a computer in real-time. Typically mounted on the ship's seawater intake, the SBE21 connects to an AC-powered interface box near a computer. TH interface box provides power and an isolated data interface, and contains a NMEA 0183 port for appending navigation data. There are options for auxiliary sensors using the RS-232 interface for a SBE32 temperature sensor and for four single-ended or two differential 0-5 volt A/D input channels for voltage output auxiliary sensors.

Components include internal-field conductivity cell eliminates proximity effects, which also permits use of expendable anti-foulant devices, for long-term bio-fouling protection. The thermistor is aged and pressure-protected.

Specifications

More information may be found in the SBE21 brochure.

Project Information

The Atlantic Meridional Transect (AMT) - Phase 1 (1995-2000)

Who was involved in the project?

The Atlantic Meridional Transect (AMT) programme was designed by and implemented as a collaboration between Plymouth Marine Laboratory (PML) and Southampton Oceanography Centre (SOC). The programme was hosted by Plymouth Marine Laboratory and involved additional researchers from UK and international universities throughout its duration.

What was the project about?

When AMT began in 1995 the programme provided a platform for international scientific collaboration, including the calibration and validation of SeaWiFs measurements and products. The programme provided an exceptional opportunity for nationally and internationally driven collaborative research and provided a platform for excellent multi-disciplinary oceanographic research. As an in situ observation system, the data collected by the AMT consortium informed on changes in biodiversity and function of the Atlantic ecosystem during this period of rapid change to our climate and biosphere.

The scientific aims were to assess:

• mesoscale to basin scale phytoplankton processes
• the functional interpretation of bio-optical signatures
• the seasonal, regional and latitudinal variations in mesozooplankton dynamics

When was the project active?

The first phase of the AMT programme ran from 1995 to 2000 and consisted of a total of 12 cruises. A second phase of funding allowed the project to continue for the period 2002 to 2006 with a further 6 cruises.

Brief summary of the project fieldwork/data

The AMT programme undertook biological, chemical and physical oceanographic research during the annual return passage of the RRS James Clark Ross between the UK and the Falkland Islands or the RRS Discovery between the UK and Cape Town, a distance of up to 13,500 km. This transect crossed a range of ecosystems from sub-polar to tropical and from euphotic shelf seas and upwelling systems to oligotrophic mid-ocean gyres. The transect route was covered north-south in September/October and south-north in April/May of each year.

The measurements of hydrographic and bio-optical properties, plankton community structure and primary production completed on the first 12 transects (1995-2000) represent the most coherent set of repeated biogeochemical observations over ocean basin scales. This unique dataset has led to several important discoveries concerning the identification of oceanic provinces, validation of ocean colour algorithms, distributions of picoplankton, identifying new regional sinks of pCO2 and variability in rates of primary production and respiration.

Who funded the project?

The programme was funded by the Natural Environment Research Council (NERC) and further support was received from the National Aeronautics and Space Administration (NASA) with equipment and funding from the Sea-viewing Wild Field-of-view Sensor (SeaWiFS) project.

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: