Metadata Report for BODC Series Reference Number 1723815
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 quality report
The following data quality comments were made whilst screening the data:
Transmittance and backscatter
Transmittance and backscatter exhibit some periods of noisy data, particularly in cast three from cycle 1675 to 2453. There is also some variability in the surface values for casts five and 12. Only obvious spikes in the data have been flagged improbable by BODC during screening.
PAR
Data from the PAR sensor were only collected from casts 1-12 due to the loss of the CTD package on cast 13. The data collected have not been transferred at BODC due to the lack of instrument information and parameter units. However, the raw data as it arrived at BODC is available upon request.
Oxygen saturation
In casts 1-12 and 15-22 the oxygen data are exhibiting super-saturation (>100%) from the surface to approximately 50 metres depth.
Fluorescence
The profiles for casts 14-22 exhibit negative values after 100 metres depth. These values have been flagged as improbable by BODC.
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
Housing | Plastic or titanium |
Membrane | 0.5 mil- fast response, typical for profile applications 1 mil- slower response, typical for moored applications |
Depth rating | 600 m (plastic) or 7000 m (titanium) 10500 m titanium housing available on request |
Measurement range | 120% of surface saturation |
Initial accuracy | 2% of saturation |
Typical stability | 0.5% per 1000 h |
Further details can be found in the manufacturer's specification sheet.
D381 CTD instrument description
CTD unit and auxiliary sensors
The CTD configuration comprised of a Sea-Bird 9plus underwater unit, with accompanying Sea-Bird 11plus deck unit. The CTD package consisted of 2 SBE 3P temperature sensors (for both primary and secondary), 2 SBE 4C conductivity sensors (again for primary and secondary) and also a SBE 43 dissolved oxygen sensor.
Additional sensors fitted to the CTD frame included a BBRT, fluorimeter and altimeter. All sensors were used for all casts. After the loss of the original CTD package during cast 13, the sensors were replaced therefore in some cases there are mulitiple instrument serial numbers.
The table below displays the CTD package and the sensors used:
Sensor unit | Model | Serial number casts 1-12 | Serial number casts 14-22 | Full specification | Last calibration date (YYYY-MM-DD) casts 1-12 | Last calibration date (YYYY-MM-DD) casts 14-22 | Comments |
---|---|---|---|---|---|---|---|
Primary CTD deck unit | SBE 11plus | 11p-34173-0676 | 11p-34173-0676 | SBE 11 Plus | |||
CTD underwater unit | SBE 9plus | 09p-67371-1082 | 09p-46253-0869 | SBE 9 Plus | |||
Digiquartz pressure sensor | Paroscientific | 121341 | 100898 | Digiquartz pressure | 2012-03-06 | 2012-01-06 | |
Temperature sensor | SBE 3P | 3p-5277 | 3p-5494 | SBE 3P | 2012-05-08 | 2012-05-09 | Primary sensor |
Temperature sensor | SBE 3P | 3P-4105 | 3P-5495 | SBE 3P | 2012-05-08 | 2012-07-06 | Secondary sensor |
Conductivity sensor | SBE 4C | 4C-3920 | 4C-3698 | SBE 4C | 2012-03-07 | 2012-05-08 | Primary sensor |
Conductivity sensor | SBE 4C | 4C-3580 | 4C-3874 | SBE 4C | 2012-05-08 | 2012-07-12 | Secondary sensor |
Dissolved oxygen sensor | SBE 43 | 43-2262 | 43-2055 | SBE 43 | 2012-03-06 | 2012-06-27 | |
Altimeter | Benthos 916T | 874 | 47597 | Benthos 916T | 2010-03-10 | 2010-03-10 | |
BBRTD light scatter sensor | Wetlabs | 167 | 758R | Wetlabs BBRTD | 2011-07-06 | 2010-05-18 | |
Transmissometer | CTG MKII Alphatracka | 161050 | 07-6075-001 | Alphatracka MKII | 2012-02-29 | 2012-05-08 | |
Fluorimeter | CTG Aquatracka MKlll | 09-7117-001 | 088095 | CTG Aquatracka MKIII | 2011-06-20 | 2012-07-25 |
Water samples were collected from the Niskin bottles on the CTD and used for nutrient and POC/HPLC/chlorophyll analysis as well as salinity analysis using a Guildline 8400B salinometer (s/n 60839).
References
Naveira-Garabato, A. C. and Allen J.T. et al. (2012). 'Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS)'. Cruise Report No. 18 National Oceanography Centre, Southampton.
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.
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:
Excitation | Chlorophyll a | Rhodamine | Fluorescein | Turbidity |
---|---|---|---|---|
Wavelength (nm) | 430 | 500 | 485 | 440* |
Bandwidth (nm) | 105 | 70 | 22 | 80* |
Emission | Chlorophyll a | Rhodamine | Fluorescein | Turbidity |
Wavelength (nm) | 685 | 590 | 530 | 440* |
Bandwidth (nm) | 30 | 45 | 30 | 80* |
* 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.
Chelsea Technologies Group ALPHAtracka and ALPHAtracka II transmissometers
The Chelsea Technologies Group ALPHAtracka (the Mark I) and its successor, the ALPHAtracka II (the Mark II), are both accurate (< 0.3 % fullscale) transmissometers that measure the beam attenuation coefficient at 660 nm. Green (565 nm), yellow (590 nm) and blue (470 nm) wavelength variants are available on special order.
The instrument consists of a Transmitter/Reference Assembly and a Detector Assembly aligned and spaced apart by an open support frame. The housing and frame are both manufactured in titanium and are pressure rated to 6000 m depth.
The Transmitter/Reference housing is sealed by an end cap. Inside the housing an LED light source emits a collimated beam through a sealed window. The Detector housing is also sealed by an end cap. A signal photodiode is placed behind a sealed window to receive the collimated beam from the Transmitter.
The primary difference between the ALPHAtracka and ALPHAtracka II is that the Alphatracka II is implemented with surface-mount technology; this has enabled a much smaller diameter pressure housing to be used while retaining exactly the same optical train as in the Mark I. Data from the Mark II version are thus fully compatible with that already obtained with the Mark I. The performance of the Mark II is further enhanced by two electronic developments from Chelsea Technologies Group - firstly, all items are locked in a signal nulling loop of near infinite gain and, secondly, the signal output linearity is inherently defined by digital circuitry only.
Among other advantages noted above, these features ensure that the optical intensity of the Mark II, indicated by the output voltage, is accurately represented by a straight line interpolation between a reading near full-scale under known conditions and a zero reading when blanked off.
For optimum measurements in a wide range of environmental conditions, the Mark I and Mark II are available in 5 cm, 10 cm and 25 cm path length versions. Output is default factory set to 2.5 volts but can be adjusted to 5 volts on request.
Further details about the Mark II instrument are available from the Chelsea Technologies Group ALPHAtrackaII specification sheet.
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
Wavelength | 471, 532, 660 nm |
Sensitivity (m-1 sr-1) | 1.2 x 10-5 at 470 nm 7.7 x 10-6 at 532 nm 3.8 x 10-6 at 660 nm |
Typical range | ~0.0024 to 5 m-1 |
Linearity | 99% R2 |
Sample rate | up to 8Hz |
Temperature range | 0 to 30°C |
Depth rating | 600 m (standard) 6000 m (deep) |
Further details can be found in the manufacturer's specification sheet.
OSMOSIS Cruise D381 Originator's CTD Data Processing
The following information contains extracts from the D381 cruise report
Discovery cruise D381 was part of the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS) project. The cruise was split into leg A and leg B and involved the deployment of 9 moorings, 4 guard buoys and 2 gliders near the Porcupine Abyssal Plain (PAP). A wave rider buoy was also deployed in leg A of the cruise. There were also some deployments of a wire-walker mooring and a bottom mounted ADCP on the edge of the continental shelf for the FASTNET project.
Sampling Strategy
Twenty-two CTD casts were made at various stations using a stainless steel framed SBE 9 plus underwater unit and an SBE 11 deck unit. Four casts were made during leg A (D381A) and the remaining casts were made in leg B (D381B). The CTD was lowered to approximately 12 metres and held whilst the system equilibrated, it was then brought back up to approximately 3 metres before starting the cast. Casts were conducted to 500 metres and 100 metres on the second leg of the cruise.
During cast 13 the wire parted and the CTD was lost, therefore no data were returned for this cast and the CTD package was replaced for the remaining casts. Due to the loss of the sensor on cast 13, PAR data were only collected during casts 1-12.
Data Processing
The data were processed using Seabird Data Processing version 7.21a and Matlab version R2010a. The following steps were performed:
- Conversion of data from binary to ascii format 24Hz raw files.
- Screening and removal of noise.
- Correction of thermal mass of the conductivity cell and further screening.
- Calibration of salinity data.
The files were submitted to BODC in .mat format with one file for each cast.
Field Calibrations
Salinity derived from the primary conductivity-temperature sensors were calibrated against salinity derived from bottle samples at the same depths.
References
Naveira-Garabato, A. C. and Allen J.T. et al. (2012). 'Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS)'. Cruise Report No. 18 National Oceanography Centre, Southampton.
Processing by BODC of RRS Discovery cruise D381 CTD data
The data arrived at BODC in 21 matlab files representing the CTD casts conducted during cruise D381 leg A and B, one file per cast. The data contained in the files are the downcast data averaged to a 2db pressure grid. The originator specified that cond1 was the preferred conductivity channel as it was more stable and had a smaller offset than cond2, therefore only cond1 has been reformatted at BODC.
The data were reformatted to BODC in house format. The following table shows the mapping of variables from the original files to the appropriate BODC parameter codes:
Originator's Variable | Units | Description | BODC Parameter Code | Units | Comments |
---|---|---|---|---|---|
press | dbar | Pressure (spatial co-ordinate) exerted by the water body by profiling pressure sensor and corrected to read zero at sea level | PRESPR01 | dbar | No unit conversion required. |
sal1 | Dimensionless | Not reformatted as salin is the preferred salinity channel. | |||
sal2 | Dimensionless | Not reformatted as salin is the preferred salinity channel. | |||
salin | Dimensionless | Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm | PSALST01 | Dimensionless | No unit conversion required - Preferred salinity channel by originator. |
temp1 | °C | Temperature of the water body by CTD or STD | TEMPST01 | °C | ITS-90 - No unit conversion required. |
temp2 | °C | Secondary channel - not reformatted. | |||
cond1 | mS/cm | Electrical conductivity of the water body by CTD | CNDCST01 | S/m | Unit conversion = /10. |
cond2 | mS/cm | Not reformatted as cond1 is the preferred conductivity channel. | |||
fluor1 | µg/L | Concentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by in-situ chlorophyll fluorometer | CPHLPR01 | mg/m3 | Equal units - No unit conversion required. |
oxygen_umolpl | µmol/L | Concentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ sensor | DOXYZZ01 | µmol/L | No unit conversion required. |
bat | /m | Attenuance due to backscatter (unspecified single wavelength at 117 degree incidence) by the water body [particulate >unknown phase] by in-situ optical backscatter measurement | BB117XXX | /m | No unit conversion required. |
trans | % | Transmittance (unspecified wavelength) per unspecified length of the water body by transmissometer | POPTZZ01 | % | No unit conversion required. |
potemp/potemp1/potemp2 | °C | Derived channel not reformatted by BODC. | |||
par1 | unknown | Data not reformatted. Data only collected during casts 1-12. The raw data is available upon request. | |||
Potential temperature of the water body by computation using UNESCO 1983 algorithm | POTMCV01 | °C | BODC derived parameter. | ||
Sigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm | SIGTPR01 | kg/m3 | BODC derived parameter. |
The reformatted data were visualised using the in-house EDSERPLO software. Improbable data were marked by adding an appropriate quality control flag, and missing data by setting the data to an appropriate value and applying the quality control flag.
Project Information
Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS)
Background
The Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS) consortium was funded to deliver NERC's Ocean Surface Boundary Layer (OSBL) programme. Commencing in 2011, this multiple year study will combine traditional observational techniques, such as moorings and CTDs, with the latest autonomous sampling technologies (including ocean gliders), capable of delivering near real-time scientific measurements through the water column.
The OSMOSIS consortium aims to improve understanding of the OSBL, the interface between the atmosphere and the deeper ocean. This layer of the water column is thought to play a pivotal role in global climate and the productivity of our oceans.
OSMOSIS involves collaborations between scientists at various universities (Reading, Oxford, Bangor, Southampton and East Anglia) together with researchers at the National Oceanography Centre (NOC), Scottish Association for Marine Science (SAMS) and Plymouth Marine Laboratory (PML). In addition, there are a number of project partners linked to the consortium.
Scientific Objectives
- The primary goal of the fieldwork component of OSMOSIS is to obtain a year-long time series of the properties of the OSBL and its controlling 3D physical processes. This is achieved with an array of moorings (two nested clusters of 4 moorings, each centred around a central mooring) and gliders deployed near the Porcupine Abyssal Plain (PAP) observatory. Data obtained from this campaign will help with the understanding of these processes and subsequent development of associated parameterisations.
- OSMOSIS will attempt to create parameterisations for the processes which determine the evolving stratification and potential vorticity budgets of the OSBL.
- The overall legacy of OSMOSIS will be to develop new (physically based and observationally supported) parameterisations of processes that deepen and shoal the OSBL, and to implement and evaluate these parameterisations in a state-of-the-art global coupled climate model, facilitating improved weather and climate predictions.
Fieldwork
Three cruises are directly associated with the OSMOSIS consortium. Preliminary exploratory work in the Clyde Sea (September 2011) to hone techniques and strategies, followed by a mooring deployment and recovery cruise in the vicinity of the Porcupine Abyssal Plain (PAP) observatory (in late Summer 2012 and 2013 respectively). Additional opportunist ship time being factored in to support the ambitious glider operations associated with OSMOSIS.
Instrumentation
Types of instrumentation and measurements associated with the OSMOSIS observational campaign:
- Ocean gliders
- Wave rider buoys
- Towed SeaSoar surveys
- Microshear measurements
- Moored current meters, conductivity-temperature sensors and ADCPs
- Traditional shipboard measurements (including CTD, underway, discrete nutrients, LADCP, ADCP).
Contacts
Collaborator | Organisation |
---|---|
Prof. Stephen Belcher | University of Reading, U.K |
Dr. Alberto C Naveira Garabato | University of Southampton, U.K |
Data Activity or Cruise Information
Cruise
Cruise Name | D381B |
Departure Date | 2012-09-14 |
Arrival Date | 2012-10-03 |
Principal Scientist(s) | John T Allen (National Oceanography Centre, Southampton) |
Ship | RRS Discovery |
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 |