Metadata Report for BODC Series Reference Number 739383

• 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 Quality Report

The data from the sigma02 channel in all casts on JR115 are above the maximum limit of the BODC parameter code SIGTPR02 (30kg/m³). All of these data were marked with the BODC quality control flag 'M', which indicates improbable values.

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

Instrument Description

CTD unit and auxiliary sensors

The CTD unit on JR115 was a Sea-Bird 911 plus with dual temperature and conductivity sensors, an altimeter, an oxygen sensor, a PAR (photosynthetically active radiation) sensor and a fluorometer. A fin was also added to the frame to reduce rotation of the package underwater.

The temperature and conductivity sensors were connected to two SBE 5 T submersible pumps (serial numbers 2395 and 2400).

The CTD unit was connected to an SBE 32 12 position carousel water sampler (serial number 3215759- 0173) and anSBE 35 Reference Temperature Sensor (serial number 0315759-0005). For the first 6 stations, 12 Niskin bottles were fitted to the rosette, while for the later stations, bottles 2 and 3 were removed to accommodate the LADCP battery.

The salinity samples from the CTD were analysed during the cruise using the BAS Guildline Autosal model 8400B (serial number 63360). The Autosal was standardised using batch P143 and P144 Standard Seawatersupplied by Ocean Scientific International Ltd.

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.

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.

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 files for JR115 were provided by the originator in Pstar format. The 35 files selected for transfer had been bin averaged by pressure to 1db. Files averaged to 24Hz were also provided by the originator however the 1db data were considered to be of a sufficiently high resolution for processing. The headers of three files were checked for consistancy using the plisth command in Unix. Each parameter selected for transfer was assigned a parameter code as follows:

The Matlab transfer function 360 was run to convert the Pstar files into an internal NetCDF format (QXF). The transfer automatically converted the conductivity channels from mS/cm to S/m. The parameters time (s) and scanno (scans) were not selected for transfer as the data were bin averaged by pressure. Metadata from file headers were separated off into tagged ASCII files which were later used in loading data to the database. The coordinates of the QXF files were checked using Google Earth to make sure that they matched the cast locations described in the cruise report.

Data from the QXF files were visualised using the in-house editor Edserplo. Obvious data spikes were flagged as 'M', null values were flagged as 'N'. Overall, the data are of good quality and there were no significant data spikes present.

Originator's Data Processing

The following information is adapted from the cruise report for JR115.

Sampling strategy

A Conductivity-Temperature-Depth (CTD) unit was used on JR115 to vertically profile the temperature and salinity of the water column. 35 full depth stations were completed, and 2 repeat shallow stations for biogeochemical sampling only. The full depth stations included a test station, the 30 stations for the SR1b Drake Passage section, with three repeat stations south of Burdwood Bank (to collect LADCP data) and one station in the ice in the Bellingshausen Sea.

The CTD package was deployed from the mid-ships gantry and A-frame, on a single conductor torque balanced cable connected to the CTD through the BAS conducting swivel. This CTD cable was made by Rochester Cables and was hauled on the 10T traction winch. The general procedure was to start data logging, deploy, and then to stop the CTD at 10 db pressure. The pumps are water activated and typically do not operate until 30-60 seconds after the CTD is in the water. After a 2 minute soak, the package was raised to just below the surface and then continuously lowered to near bottom, with the Niskin 18 bottles being closed during the upcast. The final CTD product was formed from the calibrated downcast data averaged to 1db intervals.

The CTD data were logged via an SBE 11 plus deck unit to a 1.4GHz P4 PC, running Seasave Win32 version 5.28e (Sea-Bird Electronics Inc.). This new software is a great advance on the DOS version, allowing numerical data to be listed to the screen in real time, together with several graphs of various parameters. The data rate of recorded data for the CTD was 24 Hz.

Data Processing

At the end of each CTD cast, four files (including a binary data file, an ASCII configuration file containing calibration information, an ASCII header file containing the sensor information and a file containing the data cycles at which a bottle was closed on the rosette) were created by the Seasave module. These files were saved on the D:\ drive of the CTD PC with a separate folder for each CTD. They were also copied to the N:\ drive, as soon as possible, as a back up.

The CTD data were converted to ASCII and calibrated by running the Sea-Bird Electronics Inc. Data Processing software version 5.28f Data Conversion module. The Cell Thermal Mass module (with alpha = 0.03 and beta = 7.0) was then used to remove the conductivity cell thermal mass effects from the measured conductivity. All files were then transferred from the CTD PC to the unix system using samba.

The final unix CTD files were a 1 Hz time series for the full cast (for use in LADCP processing, for example), and a 1 db file of the downcast. To simplify any reprocessing and reduce the possibility of typo errors, the scan numbers for start_down, bottom, and end_of_cast were selected from the 24Hz file, and entered into a file called 115station_dcs. The scan number for the bottom of file was found automatically using refval. The start and end scan numbers were found from listings to the screen, judging the start of the downcast after hauling to near surface, and selecting a scan number shortly before the CTD broke surface at the end of the cast.

Field Calibrations

An initial comparison was made of 187 bottle closures at 500 m or deeper (avoiding the steep gradients in salinity and temperature within the upper part of the water column). For these comparisons the notation T₁, T₂, C₁, C₂, botC₁, botC₂ and T₃₅ is used for primary and secondary temperature and conductivity sensors, conductivities from bottle salinities and SBE35 respectively.

T1 - T2 = 0.0007 ± 0.0015 °C
T1 - T35 = -0.00065 ± 0.0083 °C
T2 - T35 = -0.0014 ± 0.0083 °C
C1 - C2 = -0.0091 ± 0.0012 mmho cm^-1
botC1 - C1 = 0.0128 ± 0.0015 mmho cm^-1
botC2 - C2 = 0.0029 ± 0.0014 mmho cm^-1

On this basis it was decided to use the primary temperature sensor and the secondary conductivity sensor. An offset of 0.0029 was applied to the conductivity sensor.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Drake Passage

The World Ocean Circulation Experiment (WOCE, 1990-1998) was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate.

The Drake Passage is the narrowest constriction of the Antarctic Circumpolar Current (ACC) - the largest current in the world and connects all three major oceanic basins both horizontally and vertically, thus being a key control in the global overturning circulation.Within the Drake Passage, two repeat hydrographic sections (SR1 and SR1b) were established by WOCE. These were designed to extend measurements collected earlier by the International Southern Ocean Studies (ISOS) programme and have continued beyond the WOCE time-frame.

The original section was SR1 (which also covers part of the A21 one time survey track). Subsequently, the section was shifted to the east (and designated SR1b) in order for it to lie on a satellite ground track as illustrated in the image below.

In addition to the hydrographic measurements, UK research in Drake Passage also includes a network of coastal and deep tide gauges, analysis of satellite altimeter data, and state-of-the-art global numerical modeling.

Related Fixed Station activities are detailed in Appendix 1

Fixed Station Information

World Ocean Circulation Experiment (WOCE) Southern Repeat Section 1B - Falkland Islands to Elephant Island

WOCE Southern Repeat Section 1B is a section across Drake Passage in the South Atlantic Ocean. The nominal end points of the section (to date) are at 52° 55.74' S, 58° 00.00' W (at the south of the Falkland Islands) and 61° 03.05' S, 54° 33.10' W (off Elephant Island at the north end of the Antarctic Peninsula).

The section was first occupied by the R/V Polarstern in 1992 (Gersonde, 1993). The first UK occupation of SR1b followed on RRS Discovery later the same year. The National Oceanography Centre, Southampton (formerly known as Southampton Oceanography Centre), in collaboration with the British Antarctic Survey, have occupied the section most years since 1993 on the RRS James Clark Ross. Additionally, there were three Spanish occupations on R/V Hespérides in February 1995, 1996 and 1998 (Garcia et al., 2002). A Drake Passage summary report for RRS James Clark Ross cruises between 1993 - 2000 has been produced.

A table of cruises which occupied SR1b is presented below with links to the relevant cruise reports (were available).

References

García, M. A., I. Bladé, A. Cruzado, Z. Velásquez, H. García, J. Puigdefàbregas and J. Sospedra, 2002: Observed variability of water properties and transports on the World Ocean Circulation Experiment SR1b section across the Antarctic Circumpolar Current. J. Geophys. Res. 107 (C10) 3162, 10.1029/2000JC000277.

Gersonde, R., 1993: The Expedition Antarktis X/5 of RV Polarstern in 1992. Berichte zur Polarforschung, 131, 167 pp.

Related Fixed Station activities are detailed in Appendix 2

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: Drake Passage

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.