Metadata Report for BODC Series Reference Number 1202878
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
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Problem Reports
No Problem Report Found in the Database
Data Access Policy
GEOTRACES - data access conditions
Access to this data is currently restricted and it is not available via BODC's normal delivery mechanisms.
GEOTRACES data are published via the GEOTRACES IDP, available at:
Narrative Documents
BODC Processing
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 107 csv files in WOCE Exchange Format (65 standard CTD casts and 42 trace metal CTD casts). Data were reformatted to BODC internal format (subset of NETcdf). The following table shows how the variables within the csv files were mapped to the appropriate BODC parameter codes, 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.
KN204-1 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 | Comments |
---|---|---|---|
Pressure transducer | Digiquartz Temperature Compensated Pressure Sensor | 0888 | - |
Conductivity sensor | SBE 4C | 3269 | - |
Temperature sensor | SBE 3 | 4789 | - |
Dissolved oxygen | SBE 43 | 1393 | - |
Fluorometer | Seapoint | scf 2933 | - |
Transmissometer | Wetlab Cstar | CST-1035dr | 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 mm3 |
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
- Determine ocean distributions of selected TEIs at all major ocean basins
- Evaluate the sources, sinks, and internal cycling of these TEIs and thereby characterize more completely their global biogeochemical cycles
- Provide a baseline distribution in the Polar Regions as reference for assessing past and future changes.
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.
Three types of cruise are required to meet the goals set out by GEOTRACES. These are
- Section cruises - These will measure all the key parameters (see below) over the full depth of the water column. The sections were discussed and approved by the International GEOTRACES Scientific Steering Committee at the basin workshops.
- Process Studies - These will investigate a particular process relevant to the cycling of trace metal and isotopes. They must follow the "Criteria for Establishing GEOTRACES Process Studies" and be approved by the International GEOTRACES Scientific Steering Committee.
- Cruises collecting GEOTRACES compliant data - These will collect some trace element or isotope data. They must follow the GEOTRACES Intercalibration and Data Management protocols
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 | KN204 (GA03) |
Departure Date | 2011-11-06 |
Arrival Date | 2011-12-11 |
Principal Scientist(s) | Edward A Boyle (Massachusetts Institute of Technology Department of Earth Atmospheric and Planetary Sciences), Gregory A Cutter (Old Dominion University Department of Ocean, Earth and Atmospheric Sciences) |
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 |
B | nominal value |
Q | value below limit of quantification |