Metadata Report for BODC Series Reference Number 2047881

• 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.

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.

JC211 CTD Instrumentation

The Sea-Bird Scientific SBE911plus CTD was mounted on a rosette with a SBE32 carousel water sampler and 24 10-litre OTE bottles. The CTD was fitted with the following scientific 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.

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.

Biospherical Instruments QCP-2350-HP [underwater] PAR sensor

A cosine-corrected PAR quantum irradiance profiling sensor. For use in high-pressure underwater applications with 24 bit ADC systems. Measures light available for photosynthesis on a flat surface. Operation is by a single channel compressed analog output voltage that is proportional to the log of incident PAR (400-700 nm) irradiance. A variant of the QCP-2350 model, it uses a pressure-tolerant BH-4-MP connector. The sensor is designed for operation in waters to depths of up to 10,000 m.

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/Biospherical_QCP2300_QCP2350_Apr2014.pdf

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.

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.

JC211 ORCHESTRA CTD Data: Processing by BODC

The CTD data were supplied to BODC as 100 Mstar files and were converted to the BODC internal format.

During transfer the originator's variables were mapped to unique BODC parameter codes. The following table shows the parameter mapping.

Following transfer the data were screened using BODC in-house visualisation software. Improbable data values were assigned the appropriate BODC data quality flag.

JC211 ORCHESTRA Originator's CTD Data Processing

Sampling Strategy

A Conductivity-Temperature-Depth (CTD) unit was used to vertically profile the water column. The Sea-Bird Scientific SBE9plus CTD was mounted on a rosette with a SBE32 carousel water sampler and 24 10-litre OTE bottles, and was connected through the sea cable to a SBE11plus deck unit.

The JC211 cruise saw 100 fully successful CTD casts. Further information on the JC211 CTD sampling can be found on pages 15-24 and 105-121 of the JC211 cruise report.

Originator's processing

The data were processed using Sea-Bird Seasave 7.26.7.121. A script, ctd_linkscript, was run on linux to copy the cnv, hex and other files created and then the following scripts were run on Matlab:

>>ctd_all_part1

>>mdcs_03g

>>ctd_all_part2

>>mctd_checkplots

>>mctd_rawshow

>>mctd_rawedit

>>mctd_all_postedit

Mctd_all_postedit repeated all the steps needed to take data from edited raw data to finished 2dbar files. The ctd_all scripts call a sequence of other mctd scripts and a new command, mfsave, was introduced to reduce the number of steps required.

Calibration

Temperature

Inspection of early stations revealed a small offset between CTD temp1 and temp2, with the offset having a weak pressure dependence. Temp1 and temp2 were compared with SBE35 data from station 1 to 65. It was decided that temp2 showed the small pressure dependence. The following adjustments were made:

dcal.temp1 = d0.temp1 - 0.001;

dcal.temp2 = d0.temp2 - 0.0005 * d0.press/4000;

Conductivity

A total of 828 bottle salinity samples were analysed. The first adjustment to cond1 and cond2 was determined from stations 1 to 73. A pressure dependent factor was determined as follows:

dcal.cond1 = d0.cond1 * (1+interpl([-10 0 2500 5000 8000], (1.0*[0.0 0.0 -1.25 -1.0 -1.0] - 0.5)/1e3, d0.press) /35);

dcal.cond2 = d0.cond2 * (1+interpl([-10 0 2500 5000 8000], (1.0*[0.0 0.0 -0.625 0.25 0.25]+1.2)/1e3, d0.press) /35);

dcal.cond1= [ ];

stnfac = (min(stnlocal,90)-75)/(90-75);

dcal.cond1 = d0.cond1 * (1 + (stnfac * interpl([-10 0 1000 5000], (1*[ -1.5 -1.5 -0.5 -0.5] - 0.0)/1e3, d0.press) + interpl([-10 0 2500 5000 8000], (1.0*[0.0 0.0 -1.25 -1.0 -1.0] +0.5)/1e3, d0.press)) /35);

dcal.cond2= [ ];

stnfac = (min(stnlocal,90)-75)/(90-75);

dcal.cond2 = d0.cond1 * (1 + (stnfac * interpl([-10 0 1000 5000], (1*[ -1.0 -1.0 -0.5 -0.5] - 0.0)/1e3, d0.press) + interpl([-10 0 2500 5000 8000], (1.0*[0.0 0.0 -0.625 0.25 0.25] +1.2)/1e3, d0.press)) /35);

Oxygen

Samples for dissolved oxygen were taken from 476 Niskin bottles on 81 of the CTD casts. The sample data were ingested alongside the averaged standard blank values. The data were converted to concentrations, and then to umol/kg based on the CTD salinity from the sam_jc211_all.nc file. Duplicates were also sorted at this stage. The ratio between bottle and CTD oxygen was first inspected as a function of sample number, pressure, temperature, and oxygen value. For both sensors, a fairly simple pressure-dependent factor with 3 inflections points appeared appropriate to describe the ratios:

dcal.oxygen1 = d0.oxygen1 * interpl([0 2000 4000 5000], [1.03 1.04 1.043 1.042], d0.press);

dcal.oxygen2 = d0.oxygen2 * interpl([0 1500 4000 5000], [1.03 1.043 1.051 1.05], d0.press);

Other sensors

The fluorometer, transmissometer, turbidity, and up and downlooking PAR sensors had factory calibrations applied, but no further calibration nor investigation.

Problems

On station 74 the primary sensor duct was blocked with a gelatinous material, rendering the T,C, and O data unusable. Secondary sensor data are reported instead.

On station 91, the Seasave data acquisition temporarily stopped working. The software was restarted and the station was recorded in two parts, which were processed as station '501' and '502'. These were combined into a full station, 091.

The heave compensator on the CTD winch system was engaged deeper than 100 metres. In the upper 100 metres, it could not be used. The stations in the early part of the cruise had strong gradients, especially in salinity and temperature, between 50 and 100 metres, approximately. These data are badly contaminated by ship motion causing acceleration and deceleration of the package descent. The vane sensors (primary CTD sensors) are badly affected and the frame sensors (secondary CTD sensors and auxiliary sensors) are even worse. Whenever the package decelerates, i.e. slows the rate of descent because the sheave is heaved upwards, entrained water from a shallower depth rushes past the sensors and contaminates the data. Note that full reversal of the package motion is not required for this effect, just deceleration.

Project Information

Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA)

The Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) is a £8.4 million, five year (2016-2021) research programme funded by the Natural Environment Research Council (NERC). The aim of the research is to to advance the understanding of, and capability to predict, the Southern Ocean's impact on climate change via its uptake and storage of heat and carbon. The programme will significantly reduce uncertainties concerning how this uptake and storage by the ocean influences global climate, by conducting a series of unique fieldwork campaigns and innovative model developments.

Background

ORCHESTRA represents the first fully-unified activity by NERC institutes to address these challenges, and will draw in national and international partners to provide community coherence, and to build a legacy in knowledge and capability that will transcend the timescale of the programme itself.

It brings together science teams from six UK research institutions to investigate the role that the Southern Ocean plays in our changing climate and atmospheric carbon draw-down. It is led by British Antarctic Survey, in partnership with National Oceanography Centre, British Geological Survey, Plymouth Marine Laboratory, the Centre for Polar Observation and Modelling and the Sea Mammal Research Unit.

The oceans around Antarctica play a critical a key role in drawing down and storing large amounts of carbon and vast quantities of heat from from the atmosphere. Due to its remoteness and harsh environment, the Southern Ocean is the world's biggest data desert, and one of the hardest places to get right in climate models. The ORCHESTRA programme will make unique and important new measurements in the Southern Ocean using a range of techniques, including use of the world-class UK research vessel fleet, and deployments of innovative underwater robots. The new understanding obtained will guide key improvements to the current generation of computer models, and will enhance greatly our ability to predict climate into the future.

The scope of the programme includes interaction of the Southern Ocean with the atmosphere, exchange between the upper ocean mixed layer and the interior and exchange between the Southern Ocean and the global ocean.

Further details are available on the ORCHESTRA page.

Participants

Six different organisations are directly involved in research for ORCHESTRA. These institutions are:

• British Antarctic Survey (BAS)
• National Oceanography Centre (NOC)
• Plymouth Marine Laboratory (PML)
• British Geological Survey (BGS)
• Centre for Polar Observation and Modelling (CPOM)
• Sea Mammal Research Unit (SMRU)

GO-SHIP are a third party organisation that, although not directly involved with the programme, will conduct ship based observations that will also be used by ORCHESTRA.

Research details

Three Work Packages have been funded by the ORCHESTRA programme. These are described in brief below:

• Work Package 1: Interaction of the Southern ocean with the atmosphere
  WP1 will use new observations of surface fluxes and their controlling parameters in order to better constrain the exchanges of heat and carbon loss across the surface of the Southern Ocean.

• Work Package 2: Exchange between the upper ocean mixed layer and the interior.
  This work package will combine observationally-derived data and model simulations to determine and understand the exchanges between the ocean mixed layer and its interior.

• Work Package 3: Exchange between the Southern Ocean and the global ocean .
  This WP will use budget analyses of the hydrographic/tracer sections to diagnose the three-dimensional velocity field of the waters entering, leaving and recirculating within the Southern Atlantic sector of the Southern ocean.

• Fieldwork and data collection

  The campaign consists of 12 core cruises on board the NERC research vessels RRS James Clark Ross and RRS James Cook and will include hydrographic/tracer sections conducted across Drake Passage (SR1b), the northern Weddell Sea/Scotia Sea (A23), the northern rim of the Weddell Gyre (ANDREXII) and across the South Atlantic (24S). Section I6S will be performed by GO-SHIP Project Partners. Measurements will include temperature, salinity, dissolved oxygen, velocity, dissolved inorganic carbon, total alkalinity, inorganic nutrients, oxygen and carbon isotopes, and underway meteorological and surface ocean observations including pCO₂.

  Tags will be deployed on 30 Weddel seals and these will provide temperature and salinity profiles that can be used alongside the Argo data.

  Autonomous underwater ocean gliders will conduct multi-month missions and will deliver data on ocean stratification, heat content, mixed layer depth and turbulent mixing over the upper 1 km, with previously-unobtainable temporal resolution. These gliders will be deployed in the Weddell Gyre and the ACC.

  Field campaigns with the MASIN meteorological aircrafts will be conducted flying out of Rothera and Halley research stations and the Falkland Islands. These campaigns will deliver information on key variables relating to air-sea fluxes (surface and air temperature, wind, humidity, atmospheric CO₂, radiation, turbulent fluxes of heat, momentum and CO₂), in different sea ice conditions and oceanic regimes.

  Eart Observation datasets will be used to inform the programme on the properties of the ocean, sea ice and atmosphere and on interactions between them.

  A cluster of 6 deep ocean moorings in the Orkney Passage will collect year round series of AABW temperatre and transport. This work connects to the NERC funded project Dynamics of the Orkney Passage Outflow (DYNOPO).

  The UK Earth System model (UKESM) and underlying physical model will be used to conduct analyses of heat and carbon uptake and transport by the Southern Ocean and their links to wider climate on decadal timescales.

  An eddy-resolving (1/12°) sector model of the ocean south of 30°S with 75 vertical levels, will be built using the NEMO model coupled to the Los Alamos sea ice (CICE) model. The improvements on the ocean boundary layer will be based from the results from the NERC-funded OSMOSIS project and the inclusion of tides.

  20-5 year runs of an adjoint model will be conducted to determine how key forcings and model states affect the uptake and subduction of heat and carbon by the ocean.

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: