Metadata Report for BODC Series Reference Number 1716591

• 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

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.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

Agilent 6890 networked gas chromatograph

A networked gas chromatograph that separates and analyses gas mixtures in water or air. The instrument includes a dual channel design supporting two inlets and two detectors. An automatic liquid sampling system is fully integrated into the mainframe control and atmospheric pressure and temperature compensation is standard. The instrument also supports 6 column oven ramps with 7 plateaus.

The 6890N is completely customisable depending on the application, with choices of inlets, columns, detectors and sampling systems. Available detectors include; flame ionization, thermal conductivity, micro-electron capture, nitrogen-phosphorus, single- or dual-wavelength flame photometric. Specialised detectors include: atomic emission, Helium ionization, sulphur chemiluminescence and pulsed discharge ionization. All detectors include electronic pneumatics control and electronic on/off for all detector gases. Carrier and makeup gas settings are selectable for He, H2, N2, and argon/methane. There is a choice of inlets including; packed purged injection port, split/splitless capillary inlet, temperature-programmable cool on-column, programmable temperature vaporizer and volatiles inlet. A full array of gas sampling and column switching valves are also available. The instrument has a 7683 ALS interface and incorporates local area network technology as standard.

The Agilent 6890N uses many of the same components as the Agilent 6850N GC producing virtually identical results, but the Agilent 6850N is only half as wide. The Agilent 6890N replaces the HP Agilent 5890 and is no longer in production.

Please see the Agilent 6890N brochure and data sheet for further details.

Instrument Description

Vertical Microstructure Profiler and support sensors

Please see the cruise report for further details of the instrumentation performance and recommendations.

Rockland Scientific FP07-38 microstructure thermistor

A fast-response temperature sensor measuring microstructure temperature fluctuations for oceanographic applications. The sensing tip is a microbead thermistor (manufactured by GE Thermometics), mounted on a 9.525 mm diameter stainless steel sting which can be attached to ocean microstructure instruments. The instrument consists of small diameter glass-coated thermistor bead, thermetically sealed onto the tip of a shock-resistant glass rod.

Specifications

Rockland Scientific SPM-38 velocity shear probe

A velocity shear probe measuring microstructure velocity fluctuations in oceans and lakes. The instrument measures a single spatial component of turbulent velocity fluctuations, in a direction perpendicular to the probes main axis. The sensing head is based upon the design by Osborn (1974) and the sensing element consists of a parabolic, flexible rubber tip. The oncoming flow produces a hydrodynamic lift force proportional to the fluctuating cross-stream velocity component u. A piezo-ceramic beam embedded in the rubber tip translates the lift force into an electric signal that is proportional to u. The length of the sensing tip (10 mm) determines the maximum wavenumber resolution of the sensor which is approximately 48 cycles per meter. The measurements can be corrected to include wavenumbers up to 150 cpm.

Specifications

References cited

Osborn, T.R., 1974. Vertical profiling of velocity microstructure. Journal of Physical Oceanography, 4, 109-115.

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.

Sea-Bird SBE 3F temperature sensor

Water temperature sensor primarily designed for use on the SBE 25 and 25plus Sealogger CTD systems but can be used as a component in custom oceanographic profiling systems or high-accuracy temperature-monitoring applications. The sensor operates over the range -5 to +35 °C and has an initial accuracy of +/-0.001°C. The sensor has a depth rating of 6800 m (aluminum housing) or 10500 m (titanium housing). The SBE 3F is an enhanced version of the SBE 3 temperature sensor.

Please see the SBE 3F specification sheet for further details.

Sea-Bird SBE 7 microstructure conductivity sensor

Microstructure conductivity sensor designed for use on marine profiling applications to characterise small scale ocean conductivity features. The sensor is primarily used for the determination of conductivity gradients but it is configured to respond to absolute conductivity as well. The SBE 7 has an accuracy typically within 0.005 S m^-1 over periods of several hours and has a high speed micro-scale resolution of 3 dbar at 100 cycles m -1 (-3 dbar at 1000 Hz). The sensor has aluminium housing and a depth rating of 6800 m.

Please see the SBE 7 specification sheet for further details.

BODC Processing

Thirty three profiles were provided by the originator in a structured Matlab format and converted into BODC internal format using standard BODC processing procedures. The following table shows how the variables within the Matlab file were mapped to appropriate BODC parameter codes:

The reformatted data were visualised using the in-house EDSERPLO software. The data were screened and quality control flags were applied to data as necessary.

Originator's Data Processing

Sampling Strategy

Thirty three Vertical Microstructure Profiler (VMP) deployments were carried out successfully. Weather conditions and the presence of ice severely restricted deployments during the SR1 section and Orkney Passage. Additional VMPs were deployed at other sections instead.

Data processing

Instrument calibrations for the VMP CTD were applied and corrections for the fact the unit was not pumped, but no external calibration either to the ship CTD or water samples were made.

A matlab routine (finestructure_processing_routine.m) was used to process the seabird finestructure. The temperature and salinity data from the CTD sensors were processed as follows:

1. Near-surface data below 10 dbar were removed to eliminate the noisy data at the near surface from influencing further processing.
2. Conductivity, temperature and pressure data were then adjusted to account for the spatial displacement between the pressure sensor (at the VMP nose) and the CTD sensors (on the VMP body).
3. The temperature, conductivity and pressure were despiked.
4. The short-term mismatch between temperature and conductivity signals due to dissimilar sensor responses and the long-time mismatch between temperature and conductivity signals due to the thermal inertia of the conductivity cell were corrected.
5. The effects of conductivity cell thermal expansion and pressure contraction were corrected.
6. Low pass filters then corrected pressure, temperature, conductivity and salinity profiles to eliminate high frequency noise.
7. Temperature, conductivity and salinity profiles were averaged in pressure bins of 0.5 dbar.

Another matlab routine (vmp_process_micro.m) was then used to convert the data to real units and to calibrate the seabird data. The epsilon and chi values are estimated by integrating the power spectra of the shear and the microtemperature gradient, respectively. The data were averaged into regular 0.5 dbar bins.

Lastly the data were averaged into 1 dbar bins and saved as a matlab structure file using a Matlab program. The average results from the two shear or microtemperature probes were used, unless a probe was noisy, in which case the noisy probe data was discarded.

Rockland Scientific Vertical Microstructure Profiler VMP 5500

A full ocean-depth untethered vertical microstructure turbulence profiler for the measurement of dissipation-scale turbulence along with temperature and conductivity for up to 5500 m depth. The instrument is fitted with pressure, temperature (SBE-3F) and conductivity (SBE-4C) sensors, three acceleration sensors, a PC104 computer data acquisition and communication system, anti-aliasing filters and a standard suite of microstructure sensors which includes two SPM-38-5 velocity shear probes, two FP07-38-5 fast thermistors and an optional microstructure conductivity probe (SBE7).

All microstructure sensors are held in the nose cone and can be exchanged or replaced in the field, without the need of disassemble the main pressure case of the VMP which can hold up to 6 microstructure probes in any combination. The main pressure case contains the pressure transducer as well as the accelerometers, electronics for signal conditioning A/D conversion and data logging, and is separated from the nose cone by a 38 mm thick bulkhead which prevents water penetration into the main pressure case.

The instrument has an aluminium frame with syntactic foam attached for floatation. Data are collected on the downcast and after reaching a pre-defined depth the profiler releases ballast weights so that the instrument becomes positively buoyant. The instrument rises to the surface with a nominal speed of 1.0 ms^-1. As a backup, there is a triple-redundancy emergency ballast release consisting of a corrosion trigger, time-out trigger and pressure rate-of-change trigger. The VMP 5500 has a strobe light and a radio beacon and can also be fitted with an Argos transmitter for locating the instrument after it has returned to the surface. The VMP 5500 was replaced by the VMP 6000 in 2010.

Please see the VMP 5500 specification sheet for further details.

Project Information

Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) project document

DIMES is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.

The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing.

DIMES includes tracer release, isopycnal following RAFOS floats, microstructure measurements, shearmeter floats, EM-APEX floats, a mooring array in Drake Passage, hydrographic observations, inverse modeling, and analysis of altimetry and numerical model output.

DIMES is sponsored by the National Science Foundation (U.S.), Natural Environment Research Council (U.K) and British Antarctic Survey (U.K.)

For more information please see the official project website at DIMES

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

North Scotia Ridge Hydrographic Section

The North Scotia Ridge Section (NSR) is a repeat hydrographic section along the ridge crest of the North Scotia Ridge running between the Falklands and South Georgia. The nominal end points of the section (to date) are 53° 57.256' S, 39° 38.702' W and 54° 23.653' S, 55° 40.552' W. It was first occupied in 2014 as part of the DIMES tracer release experiment (RRS James Clarke Ross cruise JR299) and has been repeated by the ORCHESTRA project (RRS Discovery cruise DY113) in 2020.

A table of cruises which occupied the NSR is presented below with links to the relevant cruise reports.

Related Fixed Station activities are detailed in Appendix 1

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:

Appendix 1: North Scotia Ridge Section - NSR

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.