Metadata Report for BODC Series Reference Number 806679
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
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Problem Reports
No Problem Report Found in the Database
Data Access Policy
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."
Narrative Documents
Sea Bird Electronics SBE13 Dissolved Oxygen Sensor
The SBE 13 was designed as an auxiliary sensor for Sea Bird SBE 9plus, but can fitted in custom instrumentation applications. When used with the SBE 9 Underwater Unit, a flow-through plenum improves the data quality, as the pumping water over the sensor membrane reduces the errors caused by oxygen depletion during the periods of slow or intermittent flushing and also reduces exposure to biofouling.
The output voltage is proportional to membrane current (oxygen current) and to the sensor element's membrane temperature (oxygen temperature), which is used for internal temperature compensation.
Two versions of the SBE 13 are available: the SBE 13Y uses a YSI polarographic element with replaceable membranes to provide in situ measurements up to 2000 m depth and the SBE 13B uses a Beckman polarographic element to provide in situ measurements up to 10500 m depth, depending on the sensor casing. This sensor includes a replaceable sealed electrolyte membrane cartridge.
The SBE 13 instrument has been out of production since 2001 and has been superseded by the SBE 43.
Specifications
| Measurement range | 0 to 15 mL L-1 |
| Accuracy | 0.1 mL L-1 |
| Time response | 2 s at 25°C 5 s at 0°C |
| Depth range | 2000 m (SBE 13Y- housing in anodized aluminum) 6800 m (SBE 13B- housing in anodized aluminum) 105000 m (SBE 13B- housing in titanium) |
Further details can be found in the manufacturer's specification sheet.
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:
| 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.
WET Labs WETStar Fluorometers
WET Labs WETStar fluorometers are miniature flow-through fluorometers, designed to measure relative concentrations of chlorophyll, CDOM, uranine, rhodamineWT dye, or phycoerythrin pigment in a sample of water. The sample is pumped through a quartz tube, and excited by a light source tuned to the fluorescence characteristics of the object substance. A photodiode detector measures the portion of the excitation energy that is emitted as fluorescence.
Specifications
By model:
| Chlorophyll WETStar | CDOM WETStar | Uranine WETStar | Rhodamine WETStar | Phycoerythrin WETStar | |
|---|---|---|---|---|---|
| Excitation wavelength | 460 nm | 370 nm | 485 nm | 470 nm | 525 nm |
| Emission wavelength | 695 nm | 460 nm | 530 nm | 590 nm | 575 nm |
| Sensitivity | 0.03 µg l-1 | 0.100 ppb QSD | 1 µg l-1 | - | - |
| Range | 0.03-75 µg l-1 | 0-100 ppb; 0-250 ppb | 0-4000 µg l-1 | - | - |
All models:
| Temperature range | 0-30°C |
|---|---|
| Depth rating | 600 m |
| Response time | 0.17 s analogue; 0.125 s digital |
| Output | 0-5 VDC analogue; 0-4095 counts digital |
Further details can be found in the manufacturer's specification sheet, and in the instrument manual.
Underwater PAR radiometer
Underwater PAR radiometer of unknown type. Assumed to have a spectral response of 400-700nm. Could have any type of collector (flat plate cosine collector, spherical or hemispherical).
SeaTech Transmissometer
Introduction
The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.
Specifications
- Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
- Beam diameter: 15 mm
- Transmitted beam collimation: <3 milliradians
- Receiver acceptance angle (in water): <18 milliradians
- Light source wavelength: usually (but not exclusively) 660 nm (red light)
Notes
The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.
A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.
Further details can be found in the manufacturer's Manual.
RV Dana 1198 CTD Data Documentation
Cruise Principal Scientist and Data Originator
Dr. Andy Visser, Danish Institute for Fisheries Research (DIFRES), Charlottenlund, Denmark.
Content of data series
| Parameter | Unit | Parameter code | Number of casts | Comments |
|---|---|---|---|---|
| Pressure | db | PRESPR01 | 51 | none |
| Temperature (ITS-90) | deg. C | TEMPST01 | 51 | none |
| Potential Temperature | deg. C | POTMCV01 | 51 | none |
| Salinity | PSU-78 | PSALST01 | 51 | see text |
| Sigma-theta | kg m-3 | SIGTEQ01 | 51 | see text |
| Dissolved oxygen | µmol l-1 | DOXYPR01 | 51 | good but uncalibrated |
| Oxygen saturation | percent | OXYSBB01 | 51 | good but uncalibrated |
| Chlorophyll a | µg l-1 | CPHLPR01 | 51 | calibrated from fluorescence |
| Optical attenuance | m-1 | ATTNMR01 | 51 | none |
| Total suspended sediment | mg l-1 | TSEDTR01 | 51 | calibrated from attenuance |
| Downwelling irradiance | µE m-2 s-1 | IRRDUV01 | 51 | none |
Instrumentation and data processing by originator
CTD unit and auxiliary sensors
Sea-Bird Electronics 911 Plus system fitted with the following standard Sea-Bird instruments: oxygen sensor, fluorometer (WetStar), PAR sensor for downwelling irradiance and a surface PAR sensor. In addition a 20 cm pathlength Seatech transmissometer (SN T1021) from the University of Wales, Bangor, was fitted on the CTD frame and logged with the Seabird software.
Change of sensors during the cruise: none reported.
Data were logged onto a PC running Seabird data acquisition software version Seasave 4.213 and manufacturer's calibration coefficients were applied to the raw data. In addition the conductivity and the fluorescence channels had the following calibration equations applied to the data:
| Cond(samples) = 0.999739 * Cond(CTD) | R2=0.9997 | n=39 |
| Chl a = 1.468 * Fluor + 0.1776 | R2= 0.512 | n=45 |
where Cond(samples) is the conductivity measured on water samples, Cond(CTD) is the conductivity value from the CTD sensor, Chl a (µg l-1) is the chlorophyll concentration extracted from water samples and Fluor (µg Chl a l-1) is the chlorophyll concentration calculated from the CTD fluorometer output and the manufacturer's calibration coefficients. These calibration equations were determined from linear regression of values measured on sea water samples against CTD values.
Data were supplied to BODC as Seabird ASCII files including both downcast and upcast with a binning interval of 0.5 m.
Sampling device
- Rosette sampling system equipped with 11 x 5-L Niskin bottles.
- No reversible thermometer was used.
BODC post-cruise processing and screening
Reformatting
The data were converted into BODC internal format (PXF) to allow use of in-house software tools notably the workstation graphics editor SERPLO. In addition to reformatting, the transfer program applied the following modifications to the data
- temperature was converted from ITS-68 to ITS-90 by dividing the CTD values by 1.00024.
- transmissometer readings were converted from volts to attenuance using the following algorithms
| % transmission= Volts * 20 * Va/Vb |
| attenuance (m-1) = -1 / PL * loge (% transmission / 100) |
where PL is the transmissometer pathlength in m (0.20 m), Va is the manufacturer's air reading for this instrument (Va=4.661 Volts) and Vb is the average of the air readings carried out during the cruise (Vb=4.580 Volts).
- oxygen was converted from ml l-1 to µmol l-1 by multiplying the CTD values by 44.66.
- surface PAR channel was not transferred.
Screening
Reformatted CTD data were transferred onto a high-speed graphics workstation. Using custom in-house graphics editors, downcasts and upcasts were differentiated and the limits of the downcasts and upcasts were manually flagged. 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.
Banking
Once screened on the workstation, the CTD downcasts were loaded into a database under the ORACLE Relational Database Management System.
Calibration
- Fluorometer: during screening, it was noticed that the chlorophyll concentrations predicted from the fluorescence profiles obtained during Dana D1198 were consistently lower than those observed during the two other concomitant Provess cruises PE125 and CH140. It was then found that the difference between ctd chlorophyll value and extracted chlorophyll concentration for the cruise D1198 (data originator: J. Heilmann, DIFRES, DK) was still highly correlated with extracted chlorophyll a concentration (R2=0.843) suggesting that the first calibration applied could be improved by a second calibration. The following calibration equation was subsequently determined
| Chl = 1.74 x Fluor_chl - 0.05 | R2=0.777 | n=50 |
where Chl (µg l-1) is the extracted chlorophyll concentration and Fluor_chl (µg Chl a l-1) is the chlorophyll concentration obtained after the first calibration of the CTD fluorometer.
The chlorophyll concentrations predicted from the CTD fluorometer output are now within ±0.12 µg l-1 of the extracted value (95% confidence interval) and residuals range between -0.28 and +0.20 µg l-1.
- Total suspended particulate matter concentration (TSED) was estimated at the University of Wales, Bangor, by linear regression of the concentration of total suspended particulate matter as measured on water samples by gravimetry and attenuance (ATTN) as measured by the CTD transmissometer at the time of sample collection. The resulting calibration equation is:
| TSED (mg l-1) = (ATTN - 0.39557) / 0.46891 | R2=0.373 | n=62 |
- No further calibration/correction was applied to the other channels.
Comments on data quality
- Some of the salinity and oxygen profiles showed a gradient in the upper 10 to 20 m during the downcast. Such gradient was not observed on the upcast suggesting that it was the result of an insufficient period of equilibration of the CTD pump unit. These data were therefore flagged as suspect.
- No oxygen measurement on water samples was available to calibrate the oxygen probe channel. The absolute values from the oxygen concentration and oxygen saturation channels should therefore be used with caution.
Project Information
PROcesses of Vertical Exchange in Shelf Seas (PROVESS)
Introduction
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.
Scientific Rationale
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.
Fieldwork
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:
| SNS | NNS | |
|---|---|---|
| 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 |
| Delta S | 1 | small |
| 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 |
| Internal motion | No | Yes |
| Sediment | muddy-sand | muddy-sand |
| Biology | eutrophic | oligotrophic |
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:
| Site | Ship (nationality) | Cruise Mnemonic | Date |
|---|---|---|---|
| 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 |
Data Activity or Cruise Information
Cruise
| Cruise Name | D1198 |
| Departure Date | 1998-10-14 |
| Arrival Date | 1998-10-26 |
| Principal Scientist(s) | André W Visser (Danish Institute for Fisheries Research) |
| Ship | RV Dana |
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:
| Flag | Description |
|---|---|
| Blank | Unqualified |
| < | 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.) |
| D | Thermometric depth |
| E | End of CTD Down/Up Cast |
| G | Non-taxonomic biological characteristic uncertainty |
| H | Extrapolated value |
| 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 |
| N | Null value |
| O | Improbable value - user quality control |
| P | Trace/calm |
| Q | Indeterminate |
| R | Replacement value |
| S | Estimated value |
| T | Interpolated value |
| U | Uncalibrated |
| W | Control value |
| X | Excessive difference |
SeaDataNet Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
| Flag | Description |
|---|---|
| 0 | no quality control |
| 1 | good value |
| 2 | probably good value |
| 3 | probably bad value |
| 4 | bad value |
| 5 | changed value |
| 6 | value below detection |
| 7 | value in excess |
| 8 | interpolated value |
| 9 | missing value |
| A | value phenomenon uncertain |
| B | nominal value |
| Q | value below limit of quantification |
