Metadata Report for BODC Series Reference Number 1102644

• 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

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

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

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

Instrument Descriptions -CTD unit from the Canadian Arctic GEOTRACES cruise (0903 Beaufort sea)

The CTD unit was a standard SeaBird 9/11 plus, mounted on a rosette equipped with 24 bottles each with a volume of 12 L. The CTD was run in real time at 24Hz, the table below lists detailed information about the various addition sensors.

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:

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

Dr Haardt BackScat I fluorometer

The Dr Haardt BackScat I is a backscatter fluorometer designed to detect concentrations of a variety of substances in the water column. The instrument uses a Xe-flashlight source and exhibits a fast response and low power consumption. Integrated turbidity and other sensors are available and the instrument has a titanium housing rated to a maximum depth of 6000 m.

Each fluorometer is custom-built to measure substances of interest. Available spectral ranges are visible, UV I and UV II. A range of filter units are available for the measurement of chlorophyll-a, phycoerythrin, humic acids, aromatic hydrocarbons, phenol, oils, rhodamine B, sulforhodamine, fluorescein, eosin, pyranin and naphthionate.

Seapoint Chlorophyll Fluorometer

The Seapoint Chlorophyll Fluorometer (SCF) is a low power instrument for in situ measurements of chlorophyll a. The SCF uses modulated blue LED lamps and a blue excitation filter to excite chlorophyll a. The fluorescent light emitted by the chlorophyll a passes through a red emission 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 chlorophyll a concentration. The SCF may be operated with or without a pump.

Sensor specifications, current at August 2006, are given in the table below. More information can be found at the manufacturer's web site.

Sensor Specifications

Biospherical Instruments Log Quantum Cosine Irradiance Sensor QCP-2300 & QCP-2350

The QCP-2300 is a submersible cosine-collector radiometer designed to measure irradiance over Photosynthetically Active Radiation (PAR) wavelengths. It features a constant (better than ±10%) quantum response from 400 to 700 nm with the response being sharply attenuated above 700 nm and below 400 nm.

The sensor is a blue-enhanced high stability silicon photovoltaic detector with dielectric and absorbing glass filter assembly. The output is a DC voltage typically between 0 and 5 VDC that is proportional to the log of the incident irradiance.

The QCP-2300 is specifically designed for integration with 12-bit CTD systems and dataloggers requiring a limited-range of signal input.

Specifications

Further details can be found in the manufacturer's manual.

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

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

BODC Processing- CTD data cruise 0903

Reformatting

The data arrived at BODC as 45 ASCII files, representing all the standard CTD casts collected during the GEOTRACES part of the cruise. These files were reformatted to BODC internal QXF format (subset of NETcdf).

Bottom depth was missing in the originators files for CTD casts 17, 18, 22, 26, 31, 32 and 34, this value was populated at BODC using GEBCO.

The following table shows how the variables within the ASCII files were mapped to appropriate BODC parameter codes:

Screening

Reformatted CTD data were visualised using the in-house graphical editor EDSERPLO.Quality control flags were applied to data as necessary.

Originator's Data Processing -Cruise 0903

Sampling Strategy

The Canadian IPY-GEOTRACES sampling program took place from August 27, 2009 through September 12, 2009. It was part of Leg 3a of the 2009 CCGS Amundsen Expedition in the Arctic Ocean (ArcticNet 0903). Sampling started in the Mackenzie River delta and continued into the Beaufort Sea (Shelf, slope and deep Canada Basin). A total of 45 CTD casts were performed during the cruise at 10 stations.

Data Processing

Quebec-Ocean has developed a procedure to process and quality control oceanographic data collected from a Sea-Bird CTD. This procedure should ensure both the quality and the durability of such data. The data processing is performed through the Sea-Bird SBE Data Processing program. The quality control is based on the UNESCO's algorithms and is performed through matlab toolbox developed by the Maurice-Lamontagne Institute (Fisheries and Ocean Canada).

DATA PREPARATION

After the cruise and before the CTD data was processed the following checks were made;
1.1 The configuration files were checked to make sure all calibrations are correct.
1.2. The log book and the rosette sheets are compared.
1.3. Bottle data summary files (extension .btl) are checked.
1.4. Metadata from the logbook, rosette sheets and converted file header are compared.
1.5. New calibration coefficients for SBE 43 oxygen sensor are calculated using discrete sample data.
1.6. The time alignment correction for dissolved oxygen data is computed. The oxygen data must be corrected in time relative to the pressure because of the long time constant of the sensor and because of the water time transit through the pipe. The data analysis shows that a correction of 5 seconds gives the best results.
1.7. Format bottle salinity data file for CTD comparison. Similarly to the oxygen sensor, field titrations are used to compute accurate coefficients.
1.8. Format bottle salinity data file for CTD comparison. 229 autosal measurements have been used for the comparison with the CTD data.

DATA PROCESSING

2.1.Data Conversion module: Convert raw .hex or .dat data to engineering units, and store converted data in .cnv file (all data) and/or .ros file (water bottle data).
2.2. Data Extraction. This step (performed through the Matlab software) was used to eliminate useless data such as those corresponding to sensor acclimatization period (the surface soak). Also detects the main pressure spikes which are often associated by temperature and conductivity spikes. As far as the ctd 911plus is concerned, it is necessary to detect the temperature outliers and to cancel them because the temperature values are used into the module 'Cell Thermal Mass'. Moreover, major temperature spikes have an impact upon derived variables using temperature such as salinity and oxygen from SBE43.
2.3. The Wild Edit module. Was removed from the SBE Data Processing sequence in order to keep the most the original data. The outliers will be removed by the control quality sequence.
2.4. The Filter module. Was used to apply a low-pass filter on the pressure data in order to smooth high-frequency data.
2.5. The Align CTD module. The corrections (5 seconds) have been applied to align oxygen data relative to pressure. This correction allows to resolve the systematic time delay between oxygen and pressure data which is due to the long time constant of the sensor and to the time transit of the water through the pipe.
2.6. The Cell Thermal Mass module. This module concerns the conductivity parameter. It permits to remove conductivity cell thermal mass effects. It was set with the default value. Data setup;
Thermal anomaly amplitude (alpha)=0.03
Thermal anomaly time constant (1/beta)=7
2.7. The Loop Edit module. This module marks data with bad flag value when it detects a pressure slow down or reversals.
2.8. The Derive module. This module allows to compute additional oceanographic parameters.

Quality control

The CTD data was then quality controled. Data from each cast underwent 18 different test before being inspected and flagged. Details of the processing and quality control can be found in the following report 'Geotraces-IOL 0903 CTD processing notes'

Warning: There was so much variability in the data that many profiles barely passed the quality control spike tests. The originators ended up processing the casts one by one.

Field Calibrations

Salinity: Samples were taken on many casts with small bottles of 200 mL. They were analysed with an autosal GuildLine, model 8400B. Its range goes from 0.005 to 42 and its accuracy is lessthan 0.002. The results were satisfying.

Oxygen: Oxygen sensor calibration was performed using Winkler's method and a Mettler Toledo titration machine. Reagent Blanks was performed once, results show that chemicals are still good (m lessthan 4). Oxygen was sampled on one cast. Five depths of different oxygen concentration were sampled. The results are satisfying.

The dissolved oxygen (DO) data was then processed the followay way. The calibration was first checked by comparing Winkler values with CTD-DO values in the same bottle. The DO sensor calibration coefficients were then corrected. Only the downcast data was processed. The oxygen gradient in regions of high temperature gradient is still difficult to match to the temperature gradient, but this far from being unusual.

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

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: