Metadata Report for BODC Series Reference Number 1201906


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Sea-Bird SBE 43 Dissolved Oxygen Sensor  dissolved gas sensors
Sea-Bird SBE 911plus CTD  CTD; water temperature sensor; salinity sensor
WETLabs C-Star transmissometer  transmissometers
Sea-Bird SBE 3plus (SBE 3P) temperature sensor  water temperature sensor
Sea-Bird SBE 4C conductivity sensor  salinity sensor
Seapoint Fluorescein Fluorometer  fluorometers
Instrument Mounting lowered unmanned submersible
Originating Country United States
Originator Dr William Jenkins
Originating Organization Woods Hole Oceanographic Institution Department of Physical Oceanography
Processing Status QC in progress
Project(s) GEOTRACES
 

Data Identifiers

Originator's Identifier GT10/2120
BODC Series Reference 1201906
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-10-24 09:51
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars
 

Spatial Co-ordinates

Latitude 24.00000 N ( 24° 0.0' N )
Longitude 22.00000 W ( 22° 0.0' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 0.0 m
Maximum Sensor Depth 1224.0 m
Minimum Sensor Height 3373.0 m
Maximum Sensor Height 4597.0 m
Sea Floor Depth 4597.0 m
Sensor Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
ATTNMS01 1 per metre RedMedPWCorr Attenuation (red light wavelength) per unit length of the water body by WET Labs 25cm path length transmissometer and calibration to read zero in clear water
DOXMZZXX 1 Micromoles per kilogram DissO2_Mass Concentration of oxygen {O2 CAS 7782-44-7} per unit mass of the water body [dissolved plus reactive particulate phase]
FVLTZZ01 1 Volts FlVolt Instrument output (voltage) by in-situ chlorophyll fluorometer
POPTDR01 1 Percent Trans_Red_25cm Transmittance (red light wavelength) per 25cm of the water body by 25cm path length red light transmissometer
POTMCV01 1 Degrees Celsius WC_Potemp Potential temperature of the water body by computation using UNESCO 1983 algorithm
PRESPR01 1 Decibars Pres_Z Pressure (spatial co-ordinate) exerted by the water body by profiling pressure sensor and corrected to read zero at sea level
PSALCC01 1 Dimensionless P_sal_CTD_calib Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm and calibration against independent measurements
SIGTPR01 1 Kilograms per cubic metre SigTheta Sigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
TEMPCU01 1 Degrees Celsius Uncal_CTD_Temp Temperature of the water body by CTD and NO verification against independent measurements
TVLTDZ01 1 Volts TrVolt25 Instrument output (voltage) by 25cm path length transmissometer
 

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 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

BODC Processing

Reformatting

The data arrived at BODC via The Biological and Chemical Oceanography Data Management Office (BCO-DMO) the US data management office funded to manage all US GEOTRACES data. Data was provided as 53 csv files in WOCE Exchange Format (34 standard CTD casts and 19 trace metal CTD casts), all data carried WOCE flags. Variables within the CSV files were mapped to the appropriate BODC parameter codes (see table below) and all WOCE flags were converted to BODC flags.

Originator's Parameter Name Units Description BODC Parameter Code Units Comments
CTDPRS dbar Pressure of water body on profiling pressure sensor PRESPR01 dbar -
CTDTMP °C Temperature of water column by CTD TEMPCU01 °C -
CTDSAL - Practical salinity of the water body by CTD PSALCC01 - Generated by Sea-Bird software from CTD temperature and conductivity data and calibrated against discrete samples
CTDOXY µmol/Kg Dissolved oxygen concentration from SBE 43 sensor and calibrated against discrete samples DOXMSDXX µmol/Kg -
FLUORM 0-5VDC Instrument output (voltage) by in-situ chlorophyll fluorometer FVLTZZ01 Volts Raw units no calibrations applied
TRANSM 0-5VDC Instrument output (voltage) by 25cm path length transmissometer TVLTDZ01 Volts Raw units no calibrations applied
DEPTH METERS Depth of the water body calculated from pressure - - Data not transfred
CTDNOBS - Number of observations - - Data not transfred
trans Dimensionless Transmittance (red light wavelength) per 25cm of the water body by 25cm path length red light transmissometer POPTDR01 Percent Data converted to % (*100)
Cp per meter Attenuance (red light wavelength) per unit length of the water body ATTNMS01 per meter -
- - Potential temperature of the water body by computation using UNESCO 1983 algorithm POTMCV01 Degrees Celsius Calculated by BODC
- - Sigma-theta of the water body by CTD and computation from salinity and potential temperature SIGTPR01 Kilograms per cubic metre Calculated by BODC

BODC assigned each CTD/PUMP event with a unique identifier (OID) based on the originator's event log. OID was assembled from the originator's GEOTRACES event number i.e. 2143 (event number).

Screening

Reformatted CTD data were visualised using the in-house graphical editor EDSERPLO. No data values were edited or deleted. Quality control flags were applied to data as necessary.

Sea-Bird Dissolved Oxygen Sensor SBE 43 and SBE 43F

The SBE 43 is a dissolved oxygen sensor designed for marine applications. It incorporates a high-performance Clark polarographic membrane with a pump that continuously plumbs water through it, preventing algal growth and the development of anoxic conditions when the sensor is taking measurements.

Two configurations are available: SBE 43 produces a voltage output and can be incorporated with any Sea-Bird CTD that accepts input from a 0-5 volt auxiliary sensor, while the SBE 43F produces a frequency output and can be integrated with an SBE 52-MP (Moored Profiler CTD) or used for OEM applications. The specifications below are common to both.

Specifications

Housing Plastic or titanium
Membrane

0.5 mil- fast response, typical for profile applications

1 mil- slower response, typical for moored applications

Depth rating

600 m (plastic) or 7000 m (titanium)

10500 m titanium housing available on request

Measurement range 120% of surface saturation
Initial accuracy 2% of saturation
Typical stability 0.5% per 1000 h

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

KN199-4 Instrument Descriptions

GEOTRACES carousel (GTC) CTD Unit and Auxiliary Sensors

Depth profiles for dissolved and suspended particulate TEIs were obtained using the US GEOTRACES carousel sampling system. The carousel is a Seabird aluminium frame with polyurethane powder coating that holds twenty four, 12 L GO-Flo bottles. The bottles are mounted onto pivoting polyethylene blocks with titanium pins to facilitate easy removal. The carousel has a Seabird 911+ CTD with dual temperature and conductivity sensors; all of the pressure housings and pylon are titanium, eliminating the need for zinc anodes and resulting contamination. The carousel itself is attached to a 14 mm OD, 7800 m long Kevlar conducting cable spooled onto a Dynacon traction winch with slip rings.

The table below lists detailed information about the various sensors.

Sensor Model Serial Number Calibration (UT) Comments
Pressure transducer Digiquartz Temperature Compensated Pressure Sensor 0888 31/08/2007 -
Conductivity sensor SBE 4C 3269 11/11/2009 Primary sensor
Temperature sensor SBE 3 4789 12/11/2009 Primary sensor
Dissolved oxygen SBE 43 1393 25/11/2009 -
Fluorometer Seapoint scf 2933 09/07/2007 -
Transmissometer Wetlab Cstar CST-1035dr 30/7/2010 Pathlenth 25 cm

Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers

The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.

Underwater unit

The CTD underwater unit (SBE 9 or SBE 9 plus ) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus , that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.

Temperature, conductivity and pressure sensors

The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.

The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

Additional sensors

Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.

Deck unit or SEARAM

Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus ) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus ) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus .

Specifications

Specifications for the SBE 9 plus underwater unit are listed below:

Parameter Range Initial accuracy Resolution at 24 Hz Response time
Temperature -5 to 35°C 0.001°C 0.0002°C 0.065 sec
Conductivity 0 to 7 S m -1 0.0003 S m -1 0.00004 S m -1 0.065 sec (pumped)
Pressure 0 to full scale (1400, 2000, 4200, 6800 or 10500 m) 0.015% of full scale 0.001% of full scale 0.015 sec

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

Seapoint Fluorescein Fluorometer

The Seapoint Fluorescein Fluorometer (SFF) is a low power instrument for in situ measurements of fluorescein dye. The SFF uses modulated green LED lamps and a narrow-band excitation filter to excite fluorescein. Fluorescent light emitted by the fluorescein passes through an orange filter and is detected by a silicon photodiode. The low level signal is then processed using synchronous demodulation circuitry which generates an output voltage proportional to fluorescein concentration. The SFF may be operated with or without a pump.

Sensor specifications, current at February 2014, are given in the table below. More information can be found in the manufacturer's user manual .

Sensor Specifications

Power requirements 8 - 20 VDC, 15 mA avg., 27 mA pk.
Output 0 - 5.0 VDC
Output Time Constant 0.1 sec.
Power-up transient period 0.6 sec.
Excitation Wavelength 475 nm CWL, 30 nm FWHM
Emission Wavelength 530 nm CWL, 30 nm FWHM
Sensing Volume 340 mm 3
Minimum Detectable Level 0.02 µg l -1

 

  Gain Sensitivity, V µg -1 l -1 Range, µg l -1
Sensitivity/Range 30x
10x
3x
1x
1.0
0.33
0.1
0.033
5
15
50
150

WETLabs C-Star transmissometer

This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.

Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.

This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.

Specifications

Pathlength 10 or 25 cm
Wavelength 370, 470, 530 or 660 nm
Bandwidth

~ 20 nm for wavelengths of 470, 530 and 660 nm

~ 10 to 12 nm for a wavelength of 370 nm

Temperature error 0.02 % full scale °C -1
Temperature range 0 to 30°C
Rated depth

600 m (plastic housing)

6000 m (aluminum housing)

Further details are available in the manufacturer's specification sheet or user guide .

Originator's Data Processing

CTD Data Processing

Shipboard CTD data processing was performed automatically at the end of each deployment using SIO/STS CTD processing software v.5.1.6-1. Raw CTD data and bottle trips acquired by SBE Seasave on both Windows 2000 work stations (SIOR and GT-C) were copied onto the Linux database and web server system, providing a backup of the raw data. Pre-cruise laboratory calibrations were applied, then CTD data were processed into a 0.5-second time series, bottle trips were extracted, and a 1-decibar down-cast pressure series of the data was created. The pressure-series data were used by the web service for interactive plots, sections and CTD data distribution. Time-series data, and eventually basic up-cast pressure-series data, were also available for distribution through the website.

SIOR CTD data were examined at the completion of each deployment for clean corrected sensor response and any calibration shifts. As bottle salinity and oxygen results became available, they were used to refine shipboard conductivity and oxygen sensor calibrations.

Theta-S and theta-O2 comparisons were made between down and up casts as well as between groups of adjacent deployments. Vertical sections of measured and derived properties from sensor data were checked for consistency.

For more details on CTD processing please refer to the CTD processing cruise reports.

Field Calibrations

Discrete salinity and oxygen samples were collected from each cast and used to calibrate the CTD sensor data

Calibrating the transmissometer data

Christopher Hayes (Lamont-Doherty Earth Observatory of Columbia University)

The Geotraces North Atlantic Transect consisted of two legs: KN199-4 (aka GT10) and K204 (aka GT11). Transmissometer data was collected on three deployment systems during these cruises: (1) the Geotraces rosette or carousel (GT-C) which collected contamination prone elements in Go-Flo bottles, (2) a conventional Niskin bottle rosette operated by the Ocean Data Facility out of Scripps (ODF) and (3) a CTD attached to the end of the wire used for deploying in-situ pumps (PUMP). This document describes calibration of the raw voltages (from downcasts) recorded from the ODF and GT-C transmissometers and how they were calibrated into particle beam attenuation coefficients (Cp) which should be independent of the collection system. In this calibration the PUMP data was consulted but it will be submitted separately.

Equations used (from GEOTRACES protocols, 2010; see also Bishop and Wood, 2008):

[V_CTD_ref - V_CTD_dark ] = (V_factory_ref - V_factory_dark) * (V_CTD_air - V_CTD_dark) / (V_factory_air - V_factory_dark)

Transmission (tr.) = (V_obs - V_CTD_dark) / [V_CTD_ref - V_CTD_dark ]

Cp = - 4 * ln(tr.)

V_factory_ref is the maximum voltage as reported by the factory V_factory_dark is the minimum voltage (blocked path) as reported by the factory V_factory_air is the voltage reading in clean air as reported by the factory V_CTD_air is the voltage reading in clean air (cleaned windows) reported on board V_CTD_dark is the minimum (blocked path) voltage reading reported on board V_obs is the voltage reading observed during the cast Cp is calculated here for a 25 cm path length transmissometer and is in units of [1/m].

V_CTD_air and V_CTD_dark were checked routinely at sea for the PUMP on both cruises and only occasionally on the second cruise for the GT-C and ODF. The transmissometer windows were cleaned routinely for the PUMP and GT-C on both cruises and periodically for the ODF system. Based on the relatively stability of voltages at the particle minimum (~3 km depth) for the PUMP and GT-C systems, there do not appear to be significant drift issues. This was not true for the ODF system.

The calibration equations calculations, using the shipboard voltage readings result in negative Cp values (>100% transmission) for both the GT-C and PUMP systems because the V_factory_ref is too low (presumably the distilled water used in factory calibration is more particle-rich than seawater). The maximum voltage for each system therefore had to be tuned (values listed below). The cruise-wide maximum transmission was set to about 0.997 which occurs in the deep western basin (cruise KN204 or GT11, station 12). The data from the first leg of the cruise (KN199-4 or GT10) was tuned so that the Cp profiles matched in deep water at the cross-over station (TENATSO = GT11 station 24 = GT10 station 12).

There was significant variability in the background (deep water) values on the ODF system. Either ODF had drift or windows weren't always cleaned between casts. There was also a problem with the profile shape of the transmissometer data collected by the ODF cast. The maximum voltage on the ODF casts was reached at ~1km rather than 2-3km from PUMP and GT-C. I have attempted to correct the ODF data for drift by matching Cp values at the clear water minimum (~3 km depth) with the PUMP and GT-C casts, but the profile shape problem cannot be corrected for. I therefore do not recommend using the ODF transmissometer data quantitatively; although, for large beam attenuation signals like nepheloid layers or the hydrothermal plume, Cp estimated from the ODF casts is most likely a reasonable estimate.

The Cp results for the PUMP and GT-C casts generally appear internally consistent. The PUMP did not produce reliable voltage readings for the full water column at GT10 station 11 and GT11 stations 2 and 6. The GT-C casts also sampled demi-stations, shallow casts halfway between the full depth stations. One other factor about the data collection is that the during the GT-C downcasts, there was uninterrupted descent of the transmissometer (whereas during the PUMP up- and down- casts the transmissometer is stalled during deployment and retrieval of each pump from the wire). The GT-C rosette, however, did not sample at GT11 station 4, because of time constraints. This is unfortunate because this station was observed to have most particle rich nepheloid layer of the entire cruise. In order to have one file with Cp for all the deep stations, I have pasted in the Cp values measured by the PUMP system at GT11 station 4 into the GT-C data and did a slight adjustment so the deep background values matched between the surround stations 3 and 6 (GT11) in the GT-C casts.

References:

Geotraces. 2010. Sample and sample-handing protocols for GEOTRACES Cruises. In Standards and Intercalibration Committee [ed.]. http://www.obs-vlfr.fr/GEOTRACES/libraries/documents/Intercalibration/Co....

Bishop, J.K.B., Wood, T.J., 2008. Particulate matter chemistry and dynamics in the twilight zone at VERTIGO ALOHA and K2 sites. Deep Sea Research Part I: Oceanographic Research Papers 55 (12), 1684-1706.


Project Information

GEOTRACES

Introduction

GEOTRACES is an international programme sponsored by SCOR which aims to improve our understanding of biogeochemical cycles and large-scale distribution of trace elements and their isotopes (TEIs) in the marine environment. The global field programme started in 2009 and will run for at least a decade. Before the official launch of GEOTRACES, fieldwork was carried out as part of the International Polar Year (IPY)(2007-2009) where 14 cruises were connected to GEOTRACES.

GEOTRACES is expected to become the largest programme to focus on the chemistry of the oceans and will improve our understanding of past, present and future distributions of TEIs and their relationships to important global processes.

This initiative was prompted by the increasing recognition that TEIs are playing a crucial role as regulators and recorders of important biogeochemical and physical processes that control the structure and productivity of marine ecosystems, the dispersion of contaminants in the marine environment, the level of greenhouse gases in the atmosphere, and global climate.

Scientific Objectives

GEOTRACES mission is: To identify processes and quantify fluxes that control the distribution of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions.

Three overriding goals support the GEOTRACES mission

These goals will be pursued through complementary research strategies, including observations, experiments and modelling.

Fieldwork

The central component of GEOTRACES fieldwork will be a series of cruises spanning all Ocean basins see map below.

BODC image

Three types of cruise are required to meet the goals set out by GEOTRACES. These are

IPY-GEOTRACES

The IPY-GEOTRACES programme comprised of 14 research cruises on ships from 7 nations; Australia, Canada, France, Germany, New Zealand, Japan and Russia. The cruises will not be classified in the same way as the full GEOTRACES programme since the intercalibration protocols and data management protocols had not been established before the start of the IPY. But IPY-GEOTRACES data will still be quality controlled by GDAC and in the majority of cases verified versus Intercalibration standards or protocols.

Key parameters

The key parameters as set out by the GEOTRACES science plan are as follows: Fe, Al, Zn, Mn, Cd, Cu; 15N, 13C; 230Th, 231Pa; Pb isotopes, Nd isotopes; stored sample, particles, aerosols.

Weblink:

http://www.bodc.ac.uk/geotraces/
http://www.geotraces.org/


Data Activity or Cruise Information

Cruise

Cruise Name KN199-4 (GA03)
Departure Date 2010-10-15
Arrival Date 2010-11-04
Principal Scientist(s)William J Jenkins (Woods Hole Oceanographic Institution Department of Physical Oceanography)
Ship RV Knorr

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