Metadata Report for BODC Series Reference Number 1762316

• 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

Fluorometer

The underway fluorometer may be operating close to the lower limits of detection for the instrument along much of the transect. The bench fluorometric measurements made on discrete samples collected for the extraction of chlorophyll-a recorded marked difference between the gyres and the region 7°N, whereas the underway fluorometer did not detect this pattern. The ship's fluorometer appears to show a slight decline in signal throughout the cruise until moving out of the southern Atlantic gyre towards the end of the cruise. There is no record of the fluorometer being cleaned before or during the cruise and the observed pattern may be due to biofouling of the sensor further reducing the limits of detection. For this reason the discrete underway chlorophyll-a measurement datasets should be used in preference to the ship's fluorometer, even with a post cruise calibration applied.

RRS James Clark Ross Cruise AMT23 JR300 JR20131005 Surface Hydrography Data Quality Document

Unrealistic values in the PSALSU01, TEMPSU01, TEMPHU01, SVELSG01 and CNDCSG01 channels were flagged as suspect.

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

SeaBird Digital Oceanographic Thermometer SBE38

The SBE38 is an ultra-stable thermistor that can be integrated as a remote temperature sensor with an SBE21 Thermosalinograph or an SBE 45 Micro TSG, or as a secondary temperature sensor with an SBE 16 plus, 16plus-IM, 16plus V2, 16plus-IM V2 or 19plus V2 SEACAT CTD.

Temperature is determined by applying an AC excitation to reference resistances and an ultra-stable aged thermistor. The reference resistor is a hermetically sealed VISHAY. AC excitation and ratiometric comparison using a common processing channel removes measurement errors due to parasitic thermocouples, offset voltages, leakage currents and gain errors.

The SBE38 can operate in polled sampling, where it takes one sample and transmits the data, or in continuous sampling.

Specifications

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

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.

Litre Meter flow meter

A flow meter used to monitor water flow rates for pumped systems such as ships' continuous seawater supplies.

RRS James Clark Ross Cruise AMT23 JR300 JR20131005 Surface Hydrography Instrument Description Document

SeaBird MicroTSG Thermosalinograph SBE 45

The SBE45 MicroTSG is an externally powered instrument designed for shipboard measurement of temperature and conductivity of pumped near-surface water samples. The instrument can also compute salinity and sound velocity internally.

The MicroTSG comprises a platinum-electrode glass conductivity cell and a stable, pressure-protected thermistor temperature sensor. It also contains an RS-232 port for appending the output of a remote temperature sensor, allowing for direct measurement of sea surface temperature.

The instrument can operate in Polled, Autonomous and Serial Line Sync sampling modes:

• Polled sampling: the instrument takes one sample on command
• Autonomous sampling: the instrument samples at preprogrammed intervals and does not enter quiescence (sleep) state between samples
• Serial Line Sync: a pulse on the serial line causes the instrument to wake up, sample and re-enter quiescent state automatically

Specifications

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

RRS James Clark Ross Cruise AMT23 JR300 JR20131005 Surface Hydrography Processing Procedures Document

Originator's Data Processing

The sea surface hydrography measurements were performed by a Sea Bird electronics thermosalinograph in the ship's flow through system and by a temperature sensor located near the flow through intake, at the hull. The depth of the flow through intake was 6 m. The data streams were logged every second to the SCS system and merged into a comma separated file format, and the header information was stored in .TPL files.

The surface hydrography data were also logged to the Oceanlogger.ACO file. This file exhibits four initial columns: Year (yyyy), Julian day.day fraction (days), Julian day (days), day fraction (days). The file structure then contains 10 columns with meteorological data as outlined above followed by the hydrography channels in the order: tstemp (Celsius), conductivity (S m^-1), salinity (psu), sound_velocity (m s^-1) chlorophyll (µg l^-1), sampletemp (Celsius), flowrate (l min^-1), sstemp (Celsius).

BODC Data Processing

Sea surface hydrography parameters were transferred to internal BODC format and matched against BODC parameter codes, as presented in the table below. No unit conversions were applied, as the originators units were equivalent to the units of the respective BODC parameter code units assigned. BODC processing procedures included loading of data and reduction through averaging, unit conversions, visual screening and flagging of anomalous values.

Sample Calibrations

Temperature

The hull temperature sensor data were calibrated against the CTD temperature sensors during the cruise. The data from the hull sensor at the CTD start time were compared with the temperature from the externally mounted CTD temperature at 6 decibars. The temperature offsets (CTD - Hull) were plotted against date/time and CTD sensor temperature and no outliers were identified. The relationships in the offset between sensors were then compared to the date/time and the CTD sensor temperature in separate linear regressions. There was a reasonably significant relationship between the offset and the CTD temperature (R² = 0.4824; n = 48; F = 42.8786; p = 0.91682 (intercept close to zero) and p < 0.00001 (slope not close to zero)). ).

Applying the regression between the externally mounted CTD temperature sensor and the hull mounted temperature sensor, the calibrated temperature channel data were generated.

• BODC ICALRF 7016, TEMPHG01 = 1.00835 * TEMPHU01 + 0.003175

Salinity

The SBE45 salinity data were calibrated against bench salinometer data from samples collected from the underway system during the cruise. The data from the SBE45 TSG at the discrete sampling times were compared with the bench salinometer measurements. The salinity offsets (bench - TSG) were plotted against date/time and bench salinity then outliers were identified. The relationships in the offset between TSG and bench salinometer were then compared to bench salinity using a linear regression. The regression of offset against bench salinity was not significant (R² = 0.03847; n = 83; F = 3.2407; p = 0.1342 (intercept) and p =0.07555 (slope). The mean of the calculated offsets was then applied as the correction to the TSG salinity channel (offset mean = 0.011; offset SD = 0.008; n = 83).

Applying the mean offset from the bench salinometer - TSG salinity comparison, the calibrated salinity channel data were generated.

• BODC ICALRF 6996, PSALSG01 = PSALSU01 + 0.011

Chlorophyll

The fluorometer voltage data were calibrated against extracted chlorophyll-a data from samples collected from the underway system during the cruise. Samples of seawater were collected and extracted chlorophyll-a measurements were made following Welschmeyer (1994). Each sample of 250 ml was filtered through a 47 mm 0.2 µm polycarbonate filter. The filters were then placed in a vial with 10 ml 90% acetone and left in a freezer for 24 hours. The samples were then analysed on a pre-calibrated Turner Designs Trilogy fluorometer with a non-acidified chl module (CHL NA #046) fitted.

The raw voltage data from the fluorometer at the discrete sampling times were compared with the extracted chlorophyll-a measurements. The offsets (extracted chl-a - voltage) were plotted against date/time and extracted chlorophyll-a with no outliers identified. There was a significant relationship between the offset and extracted chl-a concentration (R² = 0.992; n = 129; F = 15806.76 and p < 0.0001 for both the slope and intercept).

Applying the equation from the extracted chlorophyll-a regression, the calibrated fluorescence channel data were generated.

• BODC ICALRF 7116, CPHLUT01 = 0.47576 * CPHLUMTF + 0.09277

Project Information

No Project Information held for the Series

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: