Metadata Report for BODC Series Reference Number 1177321

• 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

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.

Instrument Description

CTD Unit and Auxiliary Sensors

The main CTD package used for D341. It consisted of a stainless steel frame fitted with a Sea-Bird SBE 911plus CTD system and 24 x 20 L Ocean Test Equipment External Spring Water Samplers. The pressure sensor was located 15 cm from the bottom of the water samplers, and 132 cm from the top of the water samplers.

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.

Chelsea Technologies Group Aquatracka MKIII fluorometer

The Chelsea Technologies Group Aquatracka MKIII is a logarithmic response fluorometer. Filters are available to enable the instrument to measure chlorophyll, rhodamine, fluorescein and turbidity.

It uses a pulsed (5.5 Hz) xenon light source discharging along two signal paths to eliminate variations in the flashlamp intensity. The reference path measures the intensity of the light source whilst the signal path measures the intensity of the light emitted from the specimen under test. The reference signal and the emitted light signals are then applied to a ratiometric circuit. In this circuit, the ratio of returned signal to reference signal is computed and scaled logarithmically to achieve a wide dynamic range. The logarithmic conversion accuracy is maintained at better than one percent of the reading over the full output range of the instrument.

Two variants of the instrument are available, both manufactured in titanium, capable of operating in depths from shallow water down to 2000 m and 6000 m respectively. The optical characteristics of the instrument in its different detection modes are visible below:

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

The instrument measures chlorophyll a, rhodamine and fluorescein with a concentration range of 0.01 µg l^-1 to 100 µg l^-1. The concentration range for turbidity is 0.01 to 100 FTU (other wavelengths are available on request).

The instrument accuracy is ± 0.02 µg l^-1 (or ± 3% of the reading, whichever is greater) for chlorophyll a, rhodamine and fluorescein. The accuracy for turbidity, over a 0 - 10 FTU range, is ± 0.02 FTU (or ± 3% of the reading, whichever is greater).

Further details are available from the Aquatracka MKIII specification sheet.

Chelsea Technologies Group ALPHAtracka and ALPHAtracka II transmissometers

The Chelsea Technologies Group ALPHAtracka (the Mark I) and its successor, the ALPHAtracka II (the Mark II), are both accurate (< 0.3 % fullscale) transmissometers that measure the beam attenuation coefficient at 660 nm. Green (565 nm), yellow (590 nm) and blue (470 nm) wavelength variants are available on special order.

The instrument consists of a Transmitter/Reference Assembly and a Detector Assembly aligned and spaced apart by an open support frame. The housing and frame are both manufactured in titanium and are pressure rated to 6000 m depth.

The Transmitter/Reference housing is sealed by an end cap. Inside the housing an LED light source emits a collimated beam through a sealed window. The Detector housing is also sealed by an end cap. A signal photodiode is placed behind a sealed window to receive the collimated beam from the Transmitter.

The primary difference between the ALPHAtracka and ALPHAtracka II is that the Alphatracka II is implemented with surface-mount technology; this has enabled a much smaller diameter pressure housing to be used while retaining exactly the same optical train as in the Mark I. Data from the Mark II version are thus fully compatible with that already obtained with the Mark I. The performance of the Mark II is further enhanced by two electronic developments from Chelsea Technologies Group - firstly, all items are locked in a signal nulling loop of near infinite gain and, secondly, the signal output linearity is inherently defined by digital circuitry only.

Among other advantages noted above, these features ensure that the optical intensity of the Mark II, indicated by the output voltage, is accurately represented by a straight line interpolation between a reading near full-scale under known conditions and a zero reading when blanked off.

For optimum measurements in a wide range of environmental conditions, the Mark I and Mark II are available in 5 cm, 10 cm and 25 cm path length versions. Output is default factory set to 2.5 volts but can be adjusted to 5 volts on request.

Further details about the Mark II instrument are available from the Chelsea Technologies Group ALPHAtrackaII specification sheet.

Chelsea Technologies Photosynthetically Active Radiation (PAR) Irradiance Sensor

This sensor was originally designed to assist the study of marine photosynthesis. With the use of logarithmic amplication, the sensor covers a range of 6 orders of magnitude, which avoids setting up the sensor range for the expected signal level for different ambient conditions.

The sensor consists of a hollow PTFE 2-pi collector supported by a clear acetal dome diverting light to a filter and photodiode from which a cosine response is obtained. The sensor can be used in moorings, profiling or deployed in towed vehicles and can measure both upwelling and downwelling light.

Specifications

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

WETLabs Single-angle Backscattering Meter ECO BB

An optical scattering sensor that measures scattering at 117°. This angle was determined as a minimum convergence point for variations in the volume scattering function induced by suspended materials and water. The measured signal is less determined by the type and size of the materials in the water and is more directly correlated to their concentration.

Several versions are available, with minor differences in their specifications:

• ECO BB(RT)provides analog or RS-232 serial output with 4000 count range
• ECO BB(RT)D adds the possibility of being deployed in depths up to 6000 m while keeping the capabilities of ECO BB(RT)
• ECO BB provides the capabilities of ECO BB(RT) with periodic sampling
• ECO BBB is similar to ECO BB but with internal batteries for autonomous operation
• ECO BBS is similar to ECO BB but with an integrated anti-fouling bio-wiper
• ECO BBSB has the capabilities of ECO BBS but with internal batteries for autonomous operation

Specifications

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

Tritech Digital Precision Altimeter PA200

This altimeter is a sonar ranging device that gives the height above the sea bed when mounted vertically. When mounted in any other attitude the sensor provides a subsea distance. It can be configured to operate on its own or under control from an external unit and can be supplied with simultaneous analogue and digital outputs, allowing them to interface to PC devices, data loggers, telemetry systems and multiplexers.

These instruments can be supplied with different housings, stainless steel, plastic and aluminum, which will limit the depth rating. There are three models available: the PA200-20S, PA200-10L and the PA500-6S, whose transducer options differ slightly.

Specifications

Common specifications are presented below

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

Paroscientific Absolute Pressure Transducers Series 3000 and 4000

Paroscientific Series 3000 and 4000 pressure transducers use a Digiquartz pressure sensor to provide high accuracy and precision data. The sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

The 3000 series of transducers includes one model, the 31K-101, whereas the 4000 series includes several models, listed in the table below. All transducers exhibit repeatability of better than ±0.01% full pressure scale, hysteresis of better than ±0.02% full scale and acceleration sensitivity of ±0.008% full scale /g (three axis average). Pressure resolution is better than 0.0001% and accuracy is typically 0.01% over a broad range of temperatures.

Differences between the models lie in their pressure and operating temperature ranges, as detailed below:

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

BODC Processing Document

The data arrived at BODC in downcast PSTAR format files (.2db) representing 66 of the CTD casts taken during the cruise. Casts where only water bottles were fired (where sensors had not been logged) were not provided. Titanium and three casts using the French CTD system were not provided as there were not enough samples to calibrate these (originator's assessment). These are available in Sea-Bird format. One cast using the French CTD system was provided in PSTAR format but was not banked at BODC because it was not calibrated against independent samples (originator's assessment). All calibrated files (65) were reformatted to the internal NetCDF format following standard BODC data banking procedures. The following table shows how the variables within the PSTAR files were mapped to appropriate BODC parameter codes:

*Secondary Sea-Bird channels were swapped to primary notation during PSTAR processing to avoid entrainment by the CTD frame.

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

Variables generated at BODC

During reformatting, oxygen saturation, potential temperature and potential density anomaly were generated at BODC. Dissolved oxygen units were converted from µmol kg^-1 to µmol L^-1 using the volume-to-mass conversion factor, TOKGPR01. The following table shows how these new variables were mapped to appropriate BODC parameter codes:

Where sigmaθ = potential density based on salinity, potential temperature and a reference pressure of 0 dbar (Fofonoff and Millard, 1983).

References Cited

Benson, B.B. and Krause, D.Jr., 1984. The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnol. Oceanog., 23, 3, 620-632.

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

Originator's Data Processing

Sampling Strategy

In total 73 CTD profiles were completed on cruise D341 using NMEP equipment. Four¹ of these profiles came from deployment of the HPSS equipment when fitted with an NMEP sea unit (16591, 16606, 16616, 16648). An earlier two profiles arising from deployment of the HPSS equipment using a sea unit belonging to the HPSS group are not reported here. Of the 73 profiles discussed here, 52 were to 1000 m. Of the remaining casts, 10 were shallower than 1000 m and 11 were deeper. Just one, at 4800 m, approached the full depth of the ocean at this location. Two CTD casts were used for water collection only (16650, 16667) and a technical slip occurred on another (16546). On these casts, bottles were fired and no sensors were logged. Only one profile was obtained using the titanium frame (16665). Water samples were taken from all CTDs in the following order; oxygen, DIC, everything else. CTD sampling depths varied according to water requirements.

Two spatial CTD surveys were conducted around the central PAP site during the cruise. The first took place from 23:13 on 20/7/09 (jday 201) to 06:45 on 25/7/09 (jday 206), comprised 31 stations (16523-16564) and covered an area 100 km x 80 km. The second took place from 16:23 on 3/8/09 (jday 215) to 05:26 on 6/8/09 (jday 218), comprised 10 stations (16627-16636) and was restricted to the boundary of an area 60 km x 40 km. Both surveys were also adversely affected by deteriorating weather: the first was cut short with the final leg (F1-F6) never completed; the second had to be adjusted to be completed in an active science period reduced by poor weather.

Further information about the CTD sampling strategy can be found in the cruise report, pages 81-82.

¹Only three profiles with HPSS equipment mounted on the NMEP CTD frame were reported in the cruise report, p81. In contrast, 4 were reported in the CTD log table (cruise report, Table 46).

Data Processing

Data were initially processed through Sea-Bird software processing using SBEDataProcessing-Win32, where manufacturer's calibrations were applied to the raw data. Data were subsequently processed through PSTAR software processing in LINUX, yielding 2 dbar-binned (downcast) and bottle (upcast) files. Briefly, data were de-spiked and routines were used to derive salinity, potential temperature and density. During PSTAR processing, the primary temperature and conductivity notation were swapped from the frame-mounted to vane-mounted pair to avoid lag (due to the entrainment of the CTD frame). Further information about the data processing can be found in the cruise report, pages 83-87.

Field Calibrations

Salinity and oxygen were calibrated (post-cruise) against independent bottle samples in a similar manner to that described on p87 of the cruise report. Briefly, discrete salinity and oxygen samples were taken on CTD profiles conducted using an NMEP frame and rosette. To remove outliers the differences between bottle and CTD estimated salinity were twice screened to exclude data-points outside 2 standard deviations of the mean. However, salinity needed to be re-calibrated post-cruise. The following calibrations were applied:

Project Information

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.

Oceans 2025 Theme 2: Marine Biogeochemical Cycles

Marine biogeochemical cycles are the key processes that control the cycling of climate-active gases within the surface ocean; the main transport mechanisms governing the supply of nutrients from deeper waters across the pycnocline; and the flux of material to deep water via the biological carbon pump. The broad aim of this Theme is to improve knowledge of major biogeochemical processes in the surface layer of the Atlantic Ocean and UK shelf seas in order to develop accurate models of these systems. This strategic research will result in predictions of how the ocean will respond to, and either ameliorate or worsen, climate change and ocean acidification.

Theme 2 comprises three Research Units and ten Work Packages. Theme 2 addresses the following pivotal biogeochemical pathways and processes:

• The oceans and shelf seas as a source and sink of climate-active gases
• The importance of the carbon and nitrogen cycles in the regulation of microbial communities and hence export and biogenic gas cycling
• The biological pump and export of carbon into the ocean's interior
• Processes that introduce nutrients into the euphotic zone
• The direct impact of a high CO₂ world (acidification) on mixed-layer biogeochemical cycles and feedbacks to the atmosphere via sea/air gas fluxes and the biological pump
• The indirect impact of a high CO₂ world (increased stratification and storminess) on the supply of nutrients to the surface layer of the ocean and hence on the biological carbon pump and air-sea gas fluxes
• Cellular processes that mediate calcification in coccolithophores and how these are impacted by environmental change with a focus on elevated CO₂ and ocean acidification
• Inter- and intra-specific genetic diversity and inter-specific physiological plasticity in coccolithophores and the consequences of rapid environmental change

The official Oceans 2025 documentation for this Theme can be found using the following link: Oceans 2025 Theme 2

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: