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Metadata Report for BODC Series Reference Number 690379


Metadata Summary

Data Description

Data Category Towed STD/CTD
Instrument Type
NameCategories
Chelsea Technologies Group MINIpack CTD-F  fluorometers; CTD; water temperature sensor; salinity sensor
Instrument Mounting towed unmanned submersible
Originating Country United Kingdom
Originator Prof Raymond Pollard
Originating Organization Southampton Oceanography Centre (now National Oceanography Centre, Southampton)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) CROZEX
 

Data Identifiers

Originator's Identifier sa15519
BODC Series Reference 690379
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2004-11-25 11:36
End Time (yyyy-mm-dd hh:mm) 2004-11-25 16:08
Nominal Cycle Interval 1.0 seconds
 

Spatial Co-ordinates

Start Latitude 45.39020 S ( 45° 23.4' S )
End Latitude 45.00250 S ( 45° 0.1' S )
Start Longitude 52.24980 E ( 52° 15.0' E )
End Longitude 49.84820 E ( 49° 50.9' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 0.0 m
Maximum Sensor or Sampling Depth 311.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum -
 

Parameters

BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ACYCAA011DimensionlessSequence number
ALATGP011DegreesLatitude north relative to WGS84 by unspecified GPS system
ALONGP011DegreesLongitude east relative to WGS84 by unspecified GPS system
CPHLPR011Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by in-situ chlorophyll fluorometer
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALMC011DimensionlessPractical salinity of the water body by moving vessel profiler (MVP) and computation using UNESCO 1983 algorithm and calibration against independent measurements
TEMPMC011Degrees CelsiusTemperature of the water body by moving vessel profiler (MVP) and verification against independent measurements
TEMPMV011Degrees CelsiusTemperature of the water body by moving vessel profiler (MVP)

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

Data quality document

The chlorophyll channel shows negative values when the SeaSoar is close to the surface. These values are suspect and the appropriate data quality control flag has been applied.

The data at the beginning and end of the series, recorded during deployment and recovery, are noisy and therefore suspect. These values have not been flagged but should be treated with caution.

Data quality document

The data during deployment and recovery (i.e the start and end of the casts) should be treated with caution.


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

Chelsea Technologies Minipack CTD-F

The Minipack CTD is a titanium/acetyl conductivity-temperature-depth system that can be used for discrete profiles, installed on a data buoy or on a towed undulator. The instrument includes conductivity, temperature, depth and fluorometer sensors, incorporating a high-performance 24-channel data logging and transmission system which allows for the acquisition of up to 16 external channels (e.g., dissolved oxygen, pH, PAR, fluorescence, turbidity, transmissance etc.).

Specifications

Sensor Type Range Accuracy Resolution
Temperature Pt resistance -2 to 35 °C 0.003 °C 0.0005 °C
Conductivity Induction cell 0 to 70 mmho cm-1 0.005 mmho cm-1 0.001 mmho cm-1
Pressure

Strain gauge with
temperature compensation

0 to 600 dbar 0.2 dbar 0.01 dbar

Optical sensor specifications

  Chlorophyll a Rhodamine Amido Rhodamine Fluorescein Nephelometer Phycoerythrin Phycocyanin
Excitation wavelengths 430/30 nm or 470/30 nm 470/30 nm 425/30 nm 480/80 nm *470/30 nm 530/30 nm 590/35 nm
Emission wavelengths 685/30 nm 590/45 nm 550/30 nm 530/30 nm *470/30 nm 580/30 nm 645/35 nm
Concentration range 0.03 - 100 µg L-1 0.03 - 100 µg L-1 0.04 - 200 µg L-1 0.03 - 100 µg L-1 *0.04 - 100 FTU 0.03 - 100 µg L-1 0.03 - 100 µg L-1
Resolution 0.01 µg L-1 0.01 µg L-1 0.025 µg L-1 0.01 µg L-1 *0.01 FTU 0.01 µg L-1 0.01 µg L-1

*the wavelengths for the turbidity filters are a customer option but must be in the range 400 to 700 nm. The same wavelength is used in both the excitation path and the emission path.

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

BODC Processing

A total of 14 files were provided to BODC in PStar format. The files were then transferred to NETCDF format using BODC generated Matlab code. During transfer the originator's variables are mapped to unique parameter codes. The following table shows the mapping of variables to the appropriate BODC parameter code.

Originator Variable Description Units BODC Parameter Code Units Comments
fluor Fluorescence mg m-3 CPHLPR01 mg m-3 -
potemp Potential temperature Deg C - - Derived variable, not transferred
press Pressure dbar PRESPR01 dbar -
salin Salinity N/A PSALMC01 N/A Calibrated against independent measurements
sigma0 Density Kg m-1 - - Derived variable, not transferred
temp Calibrated temperature Deg C TEMPMC01 Deg C Calibrated against independent measurements
temp_raw Uncalibrated temperature Deg C TEMPMV01 Deg C Uncalibrated.
- Latitude Degrees ALATGP01 Degrees -
- Longitude Degrees ALONGP01 Degrees -

The data were screened using in-house visualisation software. Suspect data points were marked with the appropriate data quality control flag. Absent data were changed to the missing data value and flagged.

Following transfer and screening of the data it was noted that the time channel did not increase monotonically throughout the file. Further investigation revealed that although the resolution was 1 Hz, the time channel didn't increase by exactly 1 second each cycle and as a result the remainders added and often a second would be missed or two or three different data cycles would be stamped with the same time. Matlab was used by BODC to create a new time channel that did increase monotonically but also preserved any gaps in the data. This created time channel was then pasted over the existing time in order to remove the duplicates.

The files provided to BODC had no positional information included in them. However, BODC do possess the navigation data and were able to match the time in the SeaSoar files with the time in the navigation files and thus extract the correct positional information which was then added to the SeaSoar data.

Originator's processing

The RSS Discovery cruises of D285 and D286 represent two legs of a cruise undertaken as part of the CROZEX project in the Southwest Indian Ocean. The first leg (D285) took place between 3rd Nov and 10th Dec 2004. The second leg (D286) took place between 13th Dec 2004 and 21st Jan 2005 with the ship docked in Port Elizabeth between legs.

Sampling strategy

Minipack 210012 was used throughout both D285 and D286. From the second major tow onwards, sa15514, the temperature calibration suffered drift which became consecutivley worse in subsequent deployments. To overcome this the Minipack was swapped (for Minipack 210035) however, the conductivity cell on this new Minipack failed to function and so the original Minipack was re-instated.

A total of 17 SeaSoar deployments were made during the two legs, including trials. There were 14 deployments where data was collected. The C21 SeaSoar system carries a Chelsea Instruments Minipack CTD-F (Conductivity, temperature, depth and fluorescence) instrument. During SeaSoar deployments data were recovered, in real time, from the PENGUIN data hndling system on SeaSoar by ftp.

Calibrations

All of the variables output by the Minipack CTD-F were calibrated using pre-set calibrations stored in the instrument firmware. The sensors sampled at 16 Hz, but the output variables were averaged to one second. Firmware calibration coefficients for the MiniPack 210012 CTD are as follows:

Calibration date: 30/01/2004

Pressure = (-1.85335 x 10-9 x bits2) + (9.46170 x 10-3 x bits) - 10.2313

Temperature = (5.15065 x 10-11 x bits2) + (5.99447 x 10-4 x bits) - 3.5094

Conductivity = (-7.16162 x 10-11 x bits2) + (1.11034 x 10-3 x bits) -0.9619

chl. conc = (0.00208 x bits) - 3.694

SS15519

The primary tool for the calibration of the MIniPack CTD data was the underway thermosalinograph (TSG) connected to the ships non-toxic supply. Comparison with the calibrated thermosalinograph data was made throughout by selecting SeaSoar MiniPack data on a depth range of 3-6 metres using datpik.

Comparison with the calibrated TSGtemp shows a constant offset nees to be applied as follows:

SeaSoar_temp = SeaSoar_temp - 0.235


Project Information

CROZet natural iron bloom EXport experiment (CROZEX)

The multidisciplinary CROZet natural iron bloom EXport experiment (CROZEX) was a major component of the Natural Environment Research Council (NERC) funded core strategic project Biophysical Interactions and Controls over Export Production (BICEP). The project is the first planned natural iron fertilisation experiment to have been conducted in the Southern Ocean.

The overall objective of CROZEX was to examine, from surface to sediment, the structure, causes and consequences of a naturally occurring phytoplankton bloom in the Southern Ocean. The Crozet Plateau was chosen as the study area. This area typically exhibits two phytoplankton blooms a year, a primary bloom in that peaks in October and a secondary bloom in December or January. Specific aims with respect to these were to:

  • Determine what limits the primary bloom
  • Determine the cause of the secondary bloom

The project was run by the George Deacon Division (GDD), now Ocean Biogeochemistry and Ecosystems (OBE) at the National Oceanography Centre Southampton (NOCS). Participants from five other university departments also contributed to the project.

The project ran from November 2004 to January 2008 with marine data collection between 3rd November 2004 and 21st January 2005. There were 2 cruises to the Crozet Islands Plateau, which are summarised in Table 1.

Table 1: Details of the RRS Discovery CROZEX cruises.

Cruise No. Dates
D285 3rd November 2004 - 10th December 2004
D286 13th December 2004 - 21st January 2005

The two cruises aimed to survey two areas at different phases of the bloom cycle described above. A control area to the south of the Crozet Islands, which is classified as High Nutrient Low Chorophyll (HNLC), where the blooms do not occur and a second area in the region of the blooms to the north of the Crozet Islands.

Sampling was undertaken at ten major stations (see Pollard et al., 2007) numbered M1 to M10. The following observations/sampling were conducted at each station where possible:

  • Several CTD casts sampling:
    • Iron (using a titanium rig)
    • 234Th
    • Physical parameters (temperature, salinity etc)
    • Oxygen
    • CO2
    • Nutrients using a stainless steel rig including a Lowered Acoustic Doppler Current Profiller (LADCP)
  • At each thorium cast there was an associated Stand Alone Pump System (SAPS) deployment
  • At some stations, a drifting PELAGRA trap was deployed for the duration of the work
  • Megacoring was undertaken at M5 and M6
  • Gravity coring was undertaken at M5, M6 and M10
  • Longhurst Hardy Plankton Recorder (LPHR) tows were undertaken at a few major stations

For each of the major stations (M1 to M10), the following were determined:

  • Primary productivity
  • New Production
  • Phytoplankton community composition
  • Bacterial activity
  • Iron
  • Nutrient drawdown
  • Thorium export

Sampling between major stations included:

  • SeaSoar runs instrumented with:
    • CTD
    • Optical Plankton Counter (OPC)
    • Fast Repetition Rate fluorimeter (FRRf)
  • Physics CTD casts on several lines
  • Argo float deployments
  • Zooplankton nets at nearly every CTD and major station
  • Underway and on-station CO2 measurements
  • Underway nutrients and radium sampling
  • 5 to 6 day ship-board iron-addition incubation experiments
  • Checks against near-real-time satellite and model data
  • Mooring deployments based on the satellite imagery in support of the CROZET (Benthic CROZEX) project.

The CROZEX cruises included 6 extra days in support of the CROZET (Benthic CROZEX) project, whose main cruise took place one year after the CROZEX cruises. The CROZET work undertaken during the CROZEX cruises was primarily the moored sediment trap deployments, although some of the coring work is applicable to both projects.

CROZEX produced significant findings in several disciplines, including confirmation that iron from Crozet fertilised the bloom and that phytoplankton production rates and most export flux estimates were much larger in the bloom area than the HNLC area (Pollard et al. 2007). Many of the project results are presented in a special CROZEX issue of Deep-Sea Research II (volume 54, 2007).

References

Pollard R., Sanders R., Lucas M. and Statham P., 2007. The Crozet natural iron bloom and export experiment (CROZEX). Deep-Sea Research II, 54, 1905-1914.


Data Activity or Cruise Information

Cruise

Cruise Name D285
Departure Date 2004-11-03
Arrival Date 2004-12-10
Principal Scientist(s)Raymond T Pollard (Southampton Oceanography Centre)
Ship RRS Discovery

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:

Flag Description
Blank Unqualified
< Below detection limit
> In excess of quoted value
A Taxonomic flag for affinis (aff.)
B Beginning of CTD Down/Up Cast
C Taxonomic flag for confer (cf.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
I Taxonomic flag for single species (sp.)
K Improbable value - unknown quality control source
L Improbable value - originator's quality control
M Improbable value - BODC quality control
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
Q value below limit of quantification