Metadata Report for BODC Series Reference Number 2154111

• 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

RRS Discovery DY157 (AMT30) CTD Data Quality Report

The transmittance data (POPTDR01) values over 100 % and Attenuance (ATTNDR01) values <0/m have been flagged by BODC .

Spikes in temperature, conductivity, salinity, density and oxygen parameters, caused by possible water ingress into the connectors during CTD024 (series reference number: 2153980), were flagged by BODC.

Chl-a peaks at ~120dbar during the CTD045 downcast (series reference number: 2154215), and 262-265dbar during CTD054 (series reference number: 2154319), were flagged because the peaks were not repeated during the upcast and was therefore anomalous.

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

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

Further details can be found in the manufacturer's specification sheet.

RRS Discovery DY157 (AMT30) CTD Instrumentation

A stainless-steel Sea-Bird 911 plus CTD system was used on cruise DY157 (AMT30). This was mounted on a SBE-32 carousel water sampler holding 24 x 20-litre Niskin bottles. The CTD was fitted with the following scientific sensors:

Some calibration dates are unavailable.

There was a fouling event at 78m on the up cast of CTD016 during which the secondary sensors became noisy. Upon recovery both the primary and secondary sensors were flushed with bleach and triton-x solutions and then thoroughly flushed with MilliQ. The frame and optical sensors were also all cleaned as there were visible signs of fouling.

There were no major technical issues with the Stainless Steel CTD suite during the cruise with only one sensor requiring changing. DWIRR was unstable during CTD021, PAR2 was replaced with PAR4 for CTD022. The issue persisted so for CTD023 PAR2 was installed with a new cable, after which no more issues occurred. The suspect cable was checked, and no faults were found, possibly a little water made its way into the connector.

During CTD024 10 modulo errors occurred causing some spikes in the data which have been flagged, however the cast completed successfully. After the completion of sampling all connections on the CTD were cleaned and inspected for water ingress, there were no further errors throughout the cruise.

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.

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:

* 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.

Biospherical Instruments QCP-2350 [underwater] PAR sensor

A cosine-corrected PAR quantum irradiance profiling sensor. For use in underwater applications with 24 bit ADC systems. Measures light available for photosynthesis on a flat surface. Operation is by a single channel compressed analog output voltage that is proportional to the log of incident PAR (400-700 nm) irradiance. The sensor is designed for operation in waters to depths of up to 2,000 m (standard) or 6,800 m (optional).

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/Biospherical_QCP2300_QCP2350_Apr2014.pdf

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

Further details can be found in the manufacturer's specification sheet.

WET Labs {Sea-Bird WETLabs} C-Star CST-25-DR transmissometer

An underwater optical beam transmissometer capable of free-space measurements or mounting in a flow tube with a pump, with underway, moored or profiling applications. The instrument outputs calculated beam attenuation, with 14-bit digital or analog output. Sample rate is up to 8 Hz and spectral bandwidth is ~20 nm. This model has a path length of 25 cm, wavelength of 650 nm (red) and is depth rated to 6000 m.

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/wetlabs_cstar_transmissometer.pdf

Originators Data Processing of CTD casts from cruise DY157 (AMT30)

Sampling Strategy

In total 57 CTD cast deployments, including 1 test cast, were used to obtain profiles of the water column and section plots along the cruise transect from a range of sensors comprising pressure, temperature, conductivity, oxygen, fluorescence, downwelling and upwelling PAR, turbidity, transmittance, and attenuance. Deployments were conventional profiling casts using 24 x 20L OTE Niskin bottles for sampling water. CTD’s were deployed, weather permitting, at pre-dawn between 03:30 and 04:00 am and at solar noon around 12:00 pm ship time each day. Overall, there were 31 pre-dawn casts and 26 noon casts, all deployments were to 500m.

Data Processing

the Sea-Bird data collection software Seasave-Win32 were used to record the raw data output from the CTD casts. Processing the raw data occurred daily, following the BODC recommended guidelines using SBE Data Processing-Win32 v7.26.7. Outlined below are the processing routines used to convert the raw CTD data into CNV files, each routine is named after each stage in brackets < >:

• Data conversion - converted raw binary Sea-Bird files to ASCII files (CNV) containing the 24 Hz data for up and down casts <DatCnv>.
• Generation of bottle files for each cast containing the mean values of all the variables at the time of bottle firing events <Bottle Summary>.
• Using the CNV files, processing routines were applied to remove pressure spikes <WildEdit>.
• The oxygen sensor was then shifted relative to the pressure by 2 seconds, to compensate for the lag in the sensor response time <AlignCTD> .
• The effect of thermal 'initia' on the conductivity cells was removed <CellTM>.
• Identification of the surface soak for each cast using <Seaplot>, removed manually and then <LoopEdit> run.
• Salinity and oxygen concentration were re-derived and density (sigma-theta) values were derived after the corrections for sensor lag and thermal inertia had been applied <Derive>.
• The CTD files produced from Sea-Bird processing were converted from 24Hz ascii files into 1 dbar downcast files for calibration and visualisation on-board <BinAverage>.
• Removal of the initial salinity and oxygen channels produced at the DatCnv stage, along with the conductivity, voltage and altimeter channels from the 1-dbar downcast files <Strip>.

Prior to processing the xmlcon files were checked to against the instrument calibration sheets to ensure the correct set up details were used.

Data were then imported and processed in Ocean Data View v5.6.5.

Calibrations

Collation of the sensor values at bottle firing generated by the <Bottle Summary> routine formed the dataset for calibrating the two CTD salinity sensors and oxygen sensor against discrete bench salinometer measurements and oxygen Winkler measurements, respectively. The fluorometer sensor was calibrated post-cruise using AC-9 data calibrated against HPLC data. The CNV files were converted to ODV format and calibrations were applied using ODV software.

To generate a calibration, an offset between the discrete water sample measurement (salinity/oxygen) and the nominal value from the sensor at bottle firing was calculated. Outliers were identified using plots of offset against the discrete sample values and a linear regression was applied.

Where the regression was strong and significant the calibration equation was derived by rearranging the regression equation:

Offset = a * Discrete sample + b

Where: offset = Discrete sample - Sensor value

To give: Calibrated value = 1/(1-a) * Sensor value + b/(1-a)

Where the regression was not significant the mean value of the offset was applied. All calibration datasets are available upon request from BODC post cruise.

Salinity

The salinity sensors were calibrated against discrete salinity measurements (autosal) versus corresponding sensor measurements from four samples on average collected from CTD casts every day. Preliminary results of the calibrations indicate good agreement between bench salinometer measurements and CTD sensor values, suggesting that there was no significant drift in the sensors. For both sensors, calibration regression parameters were calculated with 95% confidence intervals using a Robust-Regression linear model. Data have been calibrated using the following equation:

Calibrated_Salinity = Uncalibrated_Salinity + average offset

Where:
For primary salinity: average offset = -0.002645946
For secondary salinity: average offset = -0.000783871

Oxygen

Discrete oxygen Winkler titration measurements taken during the cruise did not work correctly, therefore no calibration of the SBE 43 oxygen (O2) sensors could take place.

Temperature

There were no independent measurements of temperature made during the cruise and the two CTD temperature sensors on the rig returned consistent values. There was no further calibration of these sensors.

Fluorometer

Calibration of the CTD fluorometer sensor against sample data will be carried out after the cruise against AC-9 and HPLC data.

RRS Discovery DY157 (AMT30) CTD BODC Processing

The CTD data were supplied to BODC as one ODV file which was converted to a .txt file and then transferred to the BODC internal format.

During transfer the originator's variables were mapped to unique BODC parameter codes. The following table shows the parameter mapping.

Following transfer the data were screened using BODC in-house visualisation software. Improbable data values were assigned the appropriate BODC data quality flag. Missing data values, where present, were changed to the missing data value and assigned a BODC data quality flag.

Parameters found in the file and that were not transferred are available upon request. Second sensor parameters have been removed from the final file but can also be provided on request.

Project Information

Marine LTSS: CLASS (Climate Linked Atlantic Sector Science)

Introduction

CLASS is a five year (2018 to 2023) programme, funded by the Natural Environment Research Council (NERC) and extended until March 2024.

Scientific Rationale

The ocean plays a vital role in sustaining life on planet Earth, providing us with both living resources and climate regulation. The trajectory of anthropogenically driven climate change will be substantially controlled by the ocean due to its absorption of excess heat and carbon from the atmosphere, with consequent impacts on ocean resources that remain poorly understood. In an era of rapid planetary change, expanding global population and intense resource exploitation, it is vital that there are internationally coordinated ocean observing and prediction systems so policy makers can make sound evidence-based decisions about how to manage our interaction with the ocean. CLASS will underpin the UK contribution to these systems, documenting and understanding change in the marine environment, evaluating the impact of climate change and effectiveness of conservation measures and predicting the future evolution of marine environments. Over the five-year period CLASS will enhance the cost-effectiveness of observing systems by migrating them towards cutting edge autonomous technologies and developing new sensors. Finally, CLASS will create effective engagement activities ensuring academic partners have transparent access to NERC marine science capability through graduate training partnerships and access to shipborne, lab based and autonomous facilities, and modelling capabilities.

Data Activity or Cruise Information

Cruise

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: