Metadata Report for BODC Series Reference Number 935777

• 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

Measurements made by the primary conductivity sensor (CNDCST02) from stations 1-12 have not been corrected for a pressure trend. This will effect practical salinity (PSALCC02) which is derived from this data. The data originator's have indicated that the secondary sensors (CNDCST01, TEMPCU01 and PSALCC01) should be used in preference.

Data Quality Report

Removal of PAR Sensors

The originators reported that up-welling (UWIRPP01) and down-welling (DWIRPP01) PAR sensors were removed from CTD casts performed in the dark and casts greater than 600 m in depth. The presence/absence of sensors was judged for each CTD cast in turn at BODC. Subsequently, DWIRPP01 and UWIRPP01 were deleted from series where is was clear the sensors had been removed.

Data Quality Report

Low negative values (Chlorophyll-a)

The manufacturer's calibrations applied to the Chelsea MKIII Aquatracka fluorometers did not offset to exactly zero, resulting in low negative values at zero signal. The low negative values are typically less than the accuracy of the instrument but have been flagged suspect because they have fallen below the parameter code limit.

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

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.

Benthos Programmable Sonar Altimeter (PSA) 916 and 916T

The PSA 916 is a submersible altimeter that uses the travel time of an acoustic signal to determine the distance of the instrument from a target surface. It provides the user with high resolution altitude or range data while simultaneously outputting data through a digital serial port. A wide beam angle provides for reliable and accurate range measurements under the most severe operational conditions. The instrument is electronically isolated to eliminate any potential signal interference with host instrument sensors. The PSA 916 is an upgrade of the PSA 900.

The standard model (PSA 916) has an operational depth range of 0 - 6000 m, while the titanium PSA 916T has a depth range of 0 - 10000 m. All other specifications for the two versions are the same.

Specifications

Further details can be found in the manufacturer's specification sheets for the PSA 916 and the PSA 916T.

Instrument Description

CTD Unit and Auxiliary Sensors

Two CTD packages were used during RRS James Cook cruise 31 (JC031). The first CTD package (stations 1-12) comprised a Sea-Bird 911plus CTD system, auxiliary sensors and Sea-Bird SBE 32, 24-way carousel fitted to a stainless steel frame with fin. During it's recovery at station 12 (08/02/2009), the package was pulled into the hydroboom block resulting in the total loss of the CTD package over the side. Consequently, the entire package was replaced (see below). A full description of the package is as follows:

The replacement CTD package (stations 13-84) also comprised a Sea-Bird 911plus CTD system, auxiliary sensors and Sea-Bird SBE 32, 24-way carousel fitted to a stainless steel frame with fin. The LADCP (s/n 4275) was damaged during the deployment of station 35 and was replaced prior to station 36. A full description of this package is as follows:

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.

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

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

BODC Processing

The data arrived at BODC in 84 MSTAR NetCDF format files. These represented all of the CTD casts taken during the cruise. The files did not include transmissometer or backscatter data as this was not processed by the originators. The files were reformatted to the internal QXF format using transfer function 445. Due to a pressure trend on the primary conductivity sensor, the PSO and data originator for the cruise have indicated that the secondary temperature, conductivity and salinity sensors should be used in preference to the primary sensors for stations 1-12. In addition, they have indicated that the primary sensors should be used in preference to secondary sensors for stations 13-84 because of a slight pressure trend and the poor stability of the secondary conductivity sensor at these stations. For these reasons, the files were transferred to QXF format in two groupings - stations 1-12 and stations 13-84. For stations 1-12, the secondary sensors were mapped to '*01' BODC parameter codes while the primary sensors were mapped to '*02' BODC parameter codes. For stations 13-84, the primary sensors were mapped to '*01' parameter codes instead. The following table shows how the variables of station 1-12 were mapped to appropriate BODC parameter codes:

The following table shows how the variables of stations 13-84 were mapped to appropriate BODC parameter codes:

To enable the oxygen unit conversion from µmol/kg to µmol/l, the parameter TOKGPR01 (density reciprocal) was created in the output QXF files.

The reformatted data were then visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag. Missing data were marked by both setting the data to an appropriate value and setting the quality control flag.

Reference

Fofonoff N.P. and Millard Jr. R.C., 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science, 44, 53pp.

Originator's Data Processing

Sampling Strategy

The aim of JC031 was to occupy repeats of hydrographic sections in Drake Passage. The sections studied are as follows: Section SR1 (also known as A21), which is located in Drake Passage between the Southern tip of South America and the West Antarctic Peninsula; section SR1b is located further to the east. In addition to the previous section of SR1b, extra stations were sampled on the northern side of the Burdwood Bank, located south of the Falkland Islands. The data collected during JC031 comprised physical, chemical and biological measurements. There were five main scientific teams, physics, nutrients and oxygen, carbon, CFC's and transient tracers, and biology (phytoplankton). The data will contribute to the current knowledge of the physical, chemical and biological properties in this region, and will also allow comparisons to be drawn with previous cruise data so that the change in water properties and transport through Drake Passage from west to east can be observed.

A total of 84 CTD (conductivity-temperature-depth) casts were performed during the cruise. Of these casts, 48 (stations 2-49) were taken along the SR1 transect and 35 casts (stations 50-84) were taken along the SR1b transect. A 24-bottle rosette was used to take water samples at CTD stations with the general aim of sampling the full water column. Also mounted on the frame was a LADCP (lowered acoustic doppler current profiler), fluorometer, transmissometer, PAR and a dissolved oxygen sensor. Station 1 was a test cast, allowing scientists to practice sampling. At station 12, the CTD package ran into the blocks and the CTD was lost. CTD data were collected but there were no water samples or LADCP data from this station. Consequently, station 13 was a test cast with the new package (max wire out ~100m). The CTD cast was aborted at station 34 due to loss of communications at the start of the upcast. The cast was also aborted at station 35 when electrical termination flooded at 936m on the downcast. Station 36 was a successful repeat of stations 35 and 34.

Data Processing

Initial data processing was performed on a PC using the Seabird processing software SBE Data Processing, Version 7.18. Further information about Sea-Bird processing can be found in section 1 (p1) of the technical report for this cruise. After initial processing with the Seabird routines, all data were run through MSTAR MEXEC processing, which consisted of a suite of NOCS-generated programs. This was performed in Matlab and used NetCDF file formats to store all data. Further information about MEXEC processing can be found in sections 2, 3 and 4 (from p2-6) of thetechnical report from this cruise.

Field Calibrations

Salinity

CTD salinity was calibrated against independent bottle samples. Bottle samples were taken from all unique depths on every CTD cast. They were analysed using a Guildline 8400B Autosal. Further information about the collection and analysis of salinity bottle samples can be found here. Further information about the calibration of CTD salinity can be found in section 2.3 on page 3 of thetechnical report for this cruise.

Oxygen

CTD oxygen was calibrated against independent bottle samples. Bottle samples were taken from every CTD niskin bottle that had been fired and was sampled for other analyses. Samples were analysed using the Winkler whole bottle titration method with amperometric endpoint detection. Further information about the collection and analysis of independent bottles samples can be found here. Further information about the calibration of CTD oxygen can be found in section 2.4 (pages 4-5) of thetechnical report for this cruise.

Chlorophyll-a

The fluorescence sensor was not calibrated with independent bottle samples. Chlorophyll-a bottle samples were collected during the cruise but for purposes other than CTD fluorescence sensor calibration. Consequently, it may be possible to calibrate the sensor should these samples become available at a later date.

Project Information

Oceans 2025 Theme 1, Work Package 1.3: Physical-biogeochemical budgets and mixing in the Southern Ocean

This Work Package is run by the National Oceanography Centre, Southampton (NOCS) and aims to establish regional budgets of heat, freshwater and carbon, and to develop more accurate parameterisations for predictive ocean models by quantitatively investigating diapycnal and isopycnal transport processes using observations.

Vast, though poorly quantified, amounts of anthropogenic CO2 (~20 Pg) are believed to have been absorbed into the Antarctic mode and intermediate waters. Much of this uptake is achieved in the Antarctic Circumpolar Current (ACC), involving the upwelling of North Atlantic Deep Water, its northward transport by a delicate balance between Ekman drift and eddies, followed by subduction as mode waters. Models suggest that the rate of CO2 uptake is sensitive to changes in the wind and to changes to the eddy fluxes (Mignone et al., 2005).

To predict climate change, it is essential that the size of this carbon sink be known, and the processes that control it be understood. Even the exchanges of heat and freshwater between the Atlantic and Southern Oceans are poorly known. NOCS will combine observations and modelling to quantify and understand the processes controlling property fluxes and trends in the Atlantic sector of the Southern Ocean, where the Atlantic overturning circulation is partially closed as it meets the ACC. The observational effort will be fully integrated with the international Climate Variability and Predictability (CLIVAR)/Carbon repeat hydrography program, and with the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) initiative to study mixing rates and processes; this work has been accepted as a contribution to the International Polar Year. The budgets and mixing rates inferred from field measurements will be used to both evaluate and improve numerical models.

More detailed information on this Work Package is available at pages 10 - 11 of the official Oceans 2025 Theme 1 document: Oceans 2025 Theme 1

Weblink: http://www.oceans2025.org/

References

Mignone B., Gnanadesikan A., Sarmiento JL., and Slater RD., 2005. Central role of Southern Hemisphere winds and eddies in modulating the oceanic uptake of anthropogenic carbon, Geophys Res Lett, 32 doi:101029/2005Gl024464

Oceans 2025 Theme 1: Climate, Ocean Circulation and Sea Level

Through fieldwork, analysis and modelling, Theme 1 will provide detailed knowledge of how the Atlantic, Arctic and Southern Oceans are responding to, and driving, climate change. In combination with geodetic studies, it will also improve our ability to predict global sea level and UK land movements in the century ahead.

The official Oceans 2025 documentation for this Theme is available from the following link: Oceans 2025 Theme 1

Weblink: http://www.oceans2025.org/

Climate Variability and Predictability (CLIVAR)

CLIVAR is an international research programme investigating climate variability and predictability on different time-scales and the response of the climate system to anthropogenic forcing. Climate variability, its extremes and possible future changes, has a strong impact on mankind. CLIVAR seeks to better understand and predict our climate in order to take precautions and to reduce impacts of climate variability and change on our planet. CLIVAR is one of the major components of the World Climate Research Programme (WCRP). It started in 1995 and will have a lifetime of 15 years.

The specific objectives of CLIVAR are:

• To describe and understand the physical processes responsible for climate variability and predictability on seasonal, interannual, decadal, and centennial time-scales
• To coordinate the collection and analysis of observations and the development and application of models of the coupled climate system, in cooperation with other relevant climate-research and observing programmes
• To extend the record of climate variability over the time-scales of interest through the assembly of quality controlled palaeoclimatic and instrumental data sets
• To extend the range and accuracy of seasonal to interannual climate prediction through the development of global coupled predictive models
• To understand and predict the response of the climate system to increases of radiatively active gases and aerosols and to compare these predictions to the observed climate record in order to detect the anthropogenic modification of the natural climate signal

Further information may be obtained from the Official CLIVAR Project web site and theBODC web site

Oceans 2025 - The NERC Marine Centres' Strategic Research Programme 2007-2012

Who funds the programme?

The Natural Environment Research Council (NERC) funds the Oceans 2025 programme, which was originally planned in the context of NERC's 2002-2007 strategy and later realigned to NERC's subsequent strategy (Next Generation Science for Planet Earth; NERC 2007).

Who is involved in the programme?

The Oceans 2025 programme was designed by and is to be implemented through seven leading UK marine centres. The marine centres work together in coordination and are also supported by cooperation and input from government bodies, universities and other partners. The seven marine centres are:

• National Oceanography Centre, Southampton (NOCS)
• Plymouth Marine Laboratory (PML)
• Marine Biological Association (MBA)
• Sir Alister Hardy Foundation for Marine Science (SAHFOS)
• Proudman Oceanographic Laboratory (POL)
• Scottish Association for Marine Science (SAMS)
• Sea Mammal Research Unit (SMRU)

Oceans2025 provides funding to three national marine facilities, which provide services to the wider UK marine community, in addition to the Oceans 2025 community. These facilities are:

• British Oceanographic Data Centre (BODC), hosted at POL
• Permanent Service for Mean Sea Level (PSMSL), hosted at POL
• Culture Collection of Algae and Protozoa (CCAP), hosted at SAMS

The NERC-run Strategic Ocean Funding Initiative (SOFI) provides additional support to the programme by funding additional research projects and studentships that closely complement the Oceans 2025 programme, primarily through universities.

What is the programme about?

Oceans 2025 sets out to address some key challenges that face the UK as a result of a changing marine environment. The research funded through the programme sets out to increase understanding of the size, nature and impacts of these changes, with the aim to:

• improve knowledge of how the seas behave, not just now but in the future;
• help assess what that might mean for the Earth system and for society;
• assist in developing sustainable solutions for the management of marine resources for future generations;
• enhance the research capabilities and facilities available for UK marine science.

In order to address these aims there are nine science themes supported by the Oceans 2025 programme:

• Climate, circulation and sea level (Theme 1)
• Marine biogeochemical cycles (Theme 2)
• Shelf and coastal processes (Theme 3)
• Biodiversity and ecosystem functioning (Theme 4)
• Continental margins and deep ocean (Theme 5)
• Sustainable marine resources (Theme 6)
• Technology development (Theme 8)
• Next generation ocean prediction (Theme 9)
• Integration of sustained observations in the marine environment (Theme 10)

In the original programme proposal there was a theme on health and human impacts (Theme 7). The elements of this Theme have subsequently been included in Themes 3 and 9.

When is the programme active?

The programme started in April 2007 with funding for 5 years.

Brief summary of the programme fieldwork/data

Programme fieldwork and data collection are to be achieved through:

• physical, biological and chemical parameters sampling throughout the North and South Atlantic during collaborative research cruises aboard NERC's research vessels RRS Discovery, RRS James Cook and RRS James Clark Ross;
• the Continuous Plankton Recorder being deployed by SAHFOS in the North Atlantic and North Pacific on 'ships of opportunity';
• physical parameters measured and relayed in near real-time by fixed moorings and ARGO floats;
• coastal and shelf sea observatory data (Liverpool Bay Coastal Observatory (LBCO) and Western Channel Observatory (WCO)) using the RV Prince Madog and RV Quest.

The data is to be fed into models for validation and future projections. Greater detail can be found in the Theme documents.

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: