Metadata Report for BODC Series Reference Number 2207358

• 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

All fluorescence data for casts 005, 011, and 021 have been flagged as suspect for the following reasons:

i. For casts 005 and 021;

> 30% of the total flourescence profile contained negative values, likely due to the water ingress described on page 108 of the DY090 cruise report. As there are known sensor issues for these casts, and it cannot be determined exactly when the water ingress occurred, the whole flourescence channel for both of these casts have been flagged as suspect.

ii. For cast 011;

The flourescence channel remains almost entirely constant and null, wavering between the values 0.0 and 0.1 mg m^-3. There is no indication of issues with the flourometer for cast 011 from the originator but the recording of a near constant channel is suggestive of a sensor issue, thus the channel has been flagged as suspect.

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.

DY090 COMICS Titanium and TMF CTD Data: Instrument Description

CTD Unit and Auxillary Sensors

A seabird 11plus titanium, trace metal free (TMF) CTD system was used on the DY090 cruise. This was coupled with a Seabird Carousel which had 24 10 L OTE bottles fitted.

The following sensors were installed on the TMF CTD frame:

No additional sensors were added to the frame.

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.

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.

DY090 COMICS Titanium CTD Data: Processing by BODC

Data from the 10 SBE 11plus titanium CTD casts dipped from the RRS Discovery cruise DY090 were supplied to BODC in a .csv file format.

During transfer to BODC internal NetCDF format (QXF) 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. Suspect data values were assigned appropriate BODC data quality flags. Missing data values were changed to a BODC absent data value and assigned a data quality flag.

DY090 COMICS Titanium and TMF CTD Data: Originator's Processing

Sampling Strategy

A Sea-Bird Scientific SBE 911 plus CTD was mounted on a titanium rosette with a 24-way carousel water sampler. Depending on scientific requirement, between 12-14 acid washed Niskin bottles that were modified for trace metal work were fitted to the TMF frame. A total of 10 casts were completed with the TMF CTD on cruise DY090 and only the top 1000 m of the water column was sampled. For further information on the CTD layout and operation see from page 99 of the DY090 cruise report.

Originator's Processing

All data processing was performed on workstation Eriu and followed the methods used on previous MPOC cruises, using the mexec software suite. The initial SeaBird data conversion, align, and cell thermal mass corrections were performed using SBE Data Processing software.

ctd_linkscript was used to copy files from the NMF discofs mount to Eriu and set up additional symbolic links to filenames following mstar convention. For each cast the following m-files were then run, using wrapper script ctd_all_part1: mctd_01, mctd_02a, mctd_03, mdcs_01, mdcs_02. The processes completed by wrapper ctd_all_part1.m include:

• read ASCII cnv data from ctd/ASCII_FILES/ctd_dy090_001_ctm.cnv
• convert variable names from SBE names to mexec names using data/templates/ctd_dy090_renamelist.csv
• copy raw file to 24hz file
• make oxygen hysteresis adjustment on 24hz file average to 1hz
• calculate derived variables psal, potemp
• extract information from bottom cast identified by maximum pressure

Subsequently, mdcs_03g was run to inspect the profiles and hand-select start and end times. The way oxygen time lag is handled in the SBE align algorithm, and the weak dependence of oxygen calculation on salinity, means that when air is ingested into the conductivity cell at the end of the cast, the oxygen becomes biased for a few seconds earlier than the psal. Care should therefore be taken to select a cast end time for which all important variables are free from bias. After selecting the limits for start and end, ctd_all_part2 was then run, executing mctd_04, mfir_01, mfir_02, mwin_01, mwin_03, and mwin_04. The processes completed by these scripts include:

• extract down and upcasts using scan numbers stored in dcs_dy090_001, and average into 2 dbar files (2db and 2up)
• read the data/ctd/ASCII_FILES/ctd_dy090_nnn.bl file and extract scan numbers corresponding to bottle firing events
• add time from CTD file, merging on scan number
• add CTD upcast data corresponding to bottle firing
• paste these data into the master sample file data/ctd/sam_dy090_001.nc
• load winch telemetry data from winch SCS file
• add winch wireout data to the fir_dy090_001 file
• paste winch wireout data into the master sample file

A change was made during DY090 to get ctd_all_data_part2 working: cludge for the file directory structure in mfir_01.m

The 24-Hz data were checked for spikes in either of the temperature, conductivity or oxygen sensors and, if necessary, edited using mctd_rawedit. If spikes are removed, the derived files have to be regenerated using smallscript_postedit.m. Further information on how the data were processed can be found from page 124 of the DY090 cruise report.

Problems

Water ingress was discovered during testing so a new electrical termination was performed during mobilisation on the TMF wire from the Lebus containerised winch. Following re-termination, insulation tests gave approximately 4-6 Mohms open circuit and 305 Mohms short circuited; this termination was used throughout the cruise for the TMF CTD.

During cast 005, water ingress and significant corrosion was found at the connector between the Y-splice cable and the cable to the sensor causing a step change in the Fluorescence data. Both the Y cable and sensor cable were replaced and the problem was resolved.

Again, during cast 021, a similar step change in Fluorescence was observed but this time there was no sign of water ingress at the cable. The connectors at the sensor and Y-splice cable were cleaned, silicone applied and re-mated which resolved the problem.

No further issues were experienced throughout the cruise.

Project Information

Controls over Ocean Mesopelagic Interior Carbon Storage: COMICS

COMICS is a four-year collaborative research project that aims to quantify the flow of carbon in the ocean?s ?twilight? zone in order to accurately model global climate change. This ?twilight? zone is the part of the ocean between 100m and 1000m below the sea surface, where only a small amount of light from the sun can still penetrate.

By investigating carbon dynamics in the ocean interior, COMICS will help to improve predictions of future global climate change.

The COMICS project is led by the National Oceanography Centre and is a collaboration between the British Antarctic Survey and the universities of Queen Mary London, Liverpool, Oxford and Southampton. The project received funding from the Natural Environmental Research Council and runs between April 2017 and 2021.

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: