Metadata Report for BODC Series Reference Number 779601
No Problem Report Found in the Database
Public domain 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.
The recommended acknowledgment is
"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."
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.
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.
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 for the SBE 9 plus underwater unit are listed below:
|Parameter||Range||Initial accuracy||Resolution at 24 Hz||Response time|
|Temperature||-5 to 35°C||0.001°C||0.0002°C||0.065 sec|
|Conductivity||0 to 7 S m-1||0.0003 S m-1||0.00004 S m-1||0.065 sec (pumped)|
|Pressure||0 to full scale (1400, 2000, 4200, 6800 or 10500 m)||0.015% of full scale||0.001% of full scale||0.015 sec|
Further details can be found in the manufacturer's specification sheet.
Dr Haardt BackScat 1302 fluorometer
The Dr Haardt BackScat 1302 is a backscatter fluorometer designed to detect concentrations of a variety of substances in the water column. The instrument uses a Xe-flashlight source and exhibits a fast response and low power consumption.
Each BackScat sensor is custom-built to measure substances of interest. The BackScat 1302 comprises three optical sensors integrated into one housing and includes 2 xenon flash tubes and filters for the detection of chlorophyll, yellow substance (gelbstoff) and Mie backscattering.
FS Valdiva 174 CTD Data Documentation
Cruise Principal Scientist and Data Originator
Prof. Gunther Krause, AWI, Bremerhaven, Germany.
Content of data series
|Parameter||Unit||Parameter code||Number of casts||Comments|
|Temperature (ITS90)||deg. C||TEMPST01||166||none|
|Potential temperature||deg. C||POTMCV01||166||none|
|Chlorophyll a||±g l-1||CPHLPR01||166||calibrated from fluorescence|
Instrumentation and data processing by originator
CTD unit and auxiliary sensors
Sea-Bird Electronics 911 Plus system fitted with optical sensors (Dr. Haardt, Optik Mikroelectronik) for the detection of chlorophyll fluorescence (range 0-10 µg l-1) and mie backscattering at 520 nm.
The Sea-Bird sensors were calibrated at the factory prior to the cruise. The specified accuracy was as follows: pressure ±0.35 dbar, temperature ±0.002 °C, conductivity ±0.003 mS/cm.
Change of sensors during the cruise: none reported.
Data were logged onto a PC running Seabird data acquisition software version Seasave Win32 v1.05 and manufacturer's calibration coefficients were applied to the raw data.
The fluorescence channel was calibrated by the originator against chlorophyll concentration extracted from water samples collected during the cruise (data originator: P. Tett, Napier University). The calibration equation applied was:
|Chl (µg l-1) = (Chl_volts - 0.05(±0.02)) / 0.64 (±0.03)|
Data were supplied to BODC as downcast only, binned to 0.25 m.
Rosette sampling system was equipped with 12 x 2.5-L sampling bottles.
No reversible thermometer was used.
BODC post-cruise processing and screening
The data were converted into BODC internal format to allow use of in-house software tools notably the workstation graphics editor SERPLO. In addition to reformatting, the transfer program converted the temperature data from ITS-68 to ITS-90 by dividing the CTD values by 1.00024.
Reformatted CTD data were transferred onto a high-speed graphics workstation. Downcast channels were screened graphically using custom in-house graphics editors. If present, spikes and suspicious values were manually flagged. No data values were edited or deleted; flagging was achieved by modification of the associated quality control flag to 'M' for suspicious data, 'N' for null.
All channels had already been calibrated by the data originator and no further calibration/correction was applied by BODC.
Once screened on the workstation, the CTD downcasts were loaded into a database under the ORACLE Relational Database Management System. These were later migrated for inclusion in the National Oceanographic Databank.
Comments on data quality
None to report.
PROcesses of Vertical Exchange in Shelf Seas (PROVESS)
PROVESS was an interdisciplinary study of the vertical fluxes of properties through the water column and the surface and bottom boundary layers. The project was funded by the European Community MAST-III programme (MAS3-CT97- 0159) and ran from March 1998 to May 2001.
PROVESS was based on the integration of experimental, theoretical and modelling studies with the aim of improving understanding and quantification of vertical exchange processes in the water column, in particular in the surface and benthic boundary layers and across the> pycnocline. PROVESS also explored mechanisms of physical-biological coupling in which vertical exchanges and turbulence significantly affect the environmental conditions experienced by the biota with particular reference to aggregation, flocculation, sedimentation and trophic interactions.
The experimental phase of the project was carried out at two contrasting sites in the North Sea: the northern North Sea site (NNS) and the southern North Sea site (SNS).
The two sites had the following characteristics:
|Position||52° 15.0' N, 4° 17.0' E||59° 20.0' E, 1° 00.0' E|
|Time of year||April-May||September-November|
|Water depth (m)||16||100|
|M2 max amplitude (m s-1)||0.75||0.15|
|Max current (m s-1)||1.0||0.6|
|Delta T (deg C)||mixed||7-1|
|Thermocline depth (m)||mixed||35-100|
|Halocline depth (m)||5-10||cf. thermocline depth|
|Max wind speed (m s-1)||20||25|
|Max wave height (m)||5||10|
|Max wave period (s)||8||10|
At both locations measurements were concentrated at a central position with additional measurements being made to estimate horizontal gradients. Moored instruments (including current meters, temperature and pressure sensors, fluorometers, transmissometers, nutrient analysers and meteorological sensors) were deployed between 7 September and 5 November 1998 at the NNS and between 29 March and 25 May 1999 at the SNS. Each experiment was supported by intensive measurement series made from oceanographic ships and involving turbulence dissipation profiler CTD, particle size profilers, optical profilers, benthic sampling and water bottle sampling.
Details of the cruises were as follows:
|NNS||Valdivia (GER)||VA174||5 - 17 Sep 1998|
|Dana (DK)||D1198||14 - 26 Oct 1998|
|Pelagia (NL)||PE125||19 - 30 Oct 1998|
|Challenger (UK)||CH140||22 Oct - 9 Nov 1998|
|SNS||Pelagia (NL)||PE135||29 Mar - 9 Apr 1999|
|Mitra (NL)||MT0499||19 - 30 Apr 1999|
|Belgica (BE)||BG9912||17 - 21 May 1999|
|Cruise Name||VLD174 (PROVESS N-1)|
|Principal Scientist(s)||Gunther Krause (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research)|
Complete Cruise Metadata Report is available here
No Fixed Station Information held for the Series
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|<||Below detection limit|
|>||In excess of quoted value|
|A||Taxonomic flag for affinis (aff.)|
|B||Beginning of CTD Down/Up Cast|
|C||Taxonomic flag for confer (cf.)|
|E||End of CTD Down/Up Cast|
|G||Non-taxonomic biological characteristic uncertainty|
|I||Taxonomic flag for single species (sp.)|
|K||Improbable value - unknown quality control source|
|L||Improbable value - originator's quality control|
|M||Improbable value - BODC quality control|
|O||Improbable value - user quality control|
|0||no quality control|
|2||probably good value|
|3||probably bad value|
|6||value below detection|
|7||value in excess|
|A||value phenomenon uncertain|
|Q||value below limit of quantification|