Metadata Report for BODC Series Reference Number 2221886

• 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

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.

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.

TARSAN Cruise NBP1902: CTD (Conductivity-Temperature-Depth) Instrumentation

The Sea-Bird Scientific SBE9plus CTD was mounted on a rosette with an SBE32 carousel water sampler and 24 Niskin bottles (20 L and 12 L). The SBE9plus was connected through the sea cable to an SBE11plus deck unit. The CTD package was deployed from the mid-ships gantry on a cable connected to the CTD through a conducting swivel. The CTD was fitted with the following scientific sensors:

WET Labs ECO-FL (RT)D fluorometer

A single-channel fluorometer used to measure fluorescence from chlorophyll-a, CDOM, uranine, rhodamine, phycocyanin and phycoerythrin in marine environments. The (RT) in the designation signifies both an analog and RS-232 serial output with an approximate 16,300-count range. The D designation signifies this instrument is depth rated to 6000 m. This 'Real Time' instrument is able to provide continuous operation when powered. The fluorometer can measure phytoplankton chlorophyll-a concentrations in the range 0-125 ug/l, with a sensitivity of 0.02 ug/l. The instrument can operate over the temperature range 0-30 degC.

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

WETLabs ECO-FL Fluorometer

The Environmental Characterization Optics series of single channel fluorometers are designed to measure concentrations of natural and synthetic substances in water, and are therefore useful for biological monitoring and dye trace studies. Selected excitation and emission filters allow detection of the following substances: chlorophyll-a, coloured dissolved organic matter (CDOM), uranine (fluorescein), rhodamine, phycoerythrin and phycocyanin.

The ECO-FL can operate continuously or periodically and has two different types of connectors to output the data (analogue and RS-232 serial output). The potted optics block results in long term stability of the instrument and the optional anti-biofouling technology delivers truly long term field measurements.

In addition to the standard model, five variants are available, and the differences between these and the basic ECO-FL are listed below:

• FL(RT): similar to the FL but operates continuously when power is supplied
• FL(RT)D: similar model to the (RT) but has a depth rating of 6000 m
• FLB: includes internal batteries for autonomous operation and periodic sampling
• FLS: similar to FLB but has an integrated anti-fouling bio-wiper
• FLSB: similar to the FLS, but includes internal batteries for autonomous operation

Specifications

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

Biospherical Instruments QSP-2350 underwater PAR sensor

Quantum Scalar Irradiance PAR Sensor. Developed for data loggers with limited dynamic range. It uses a scalar irradiance collector to obtain a uniform directional response over 3.6-pi steradians. A stainless���steel encased optical light pipe guides flux from the collector to a filtered silicon pho���todetector, resultng in a flat quantum response over the PAR spectral region (400���700 nm). The sensor produces a logarithmically compressed analog voltage output and BH���4���MP connector Operates in waters depths up to 2000 m.

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/Biospherical_QSP_2300_2350_series_brochure.pdf

Valeport VA500 altimeter

A titanium-housed acoustic altimeter used for underwater positioning to determine distance to or height above the seabed. Can be mounted used on ROVs, AUVs and other such platforms for various underwater construction and hydrographic applications. The VA500 features a 500kHz broadband transducer offering a range of 0.1m to 100m, a resolution of 1mm and a beam angle +/- 3 degrees. It features RS232 and RS485 digital output as standard, and is supplied with free DataLog X2 software for instrument setup and data display. An optional Valeport miniIPS pressure sensor can be added. The pressure sensor is a temperature compensated piezo-resistive sensor with various ranges available, an accuracy +/- 0.01 percent FS, and a resolution of 0.001 percent FS. The VA500 is depth-rated to 6000m.

For more information, please see this document: https://www.bodc.ac.uk/data/documents/nodb/pdf/Valeport-VA500-Altimeter-Datasheet.pdf

Paroscientific Absolute Pressure Transducers Series 3000 and 4000

Paroscientific Series 3000 and 4000 pressure transducers use a Digiquartz pressure sensor to provide high accuracy and precision data. The sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

The 3000 series of transducers includes one model, the 31K-101, whereas the 4000 series includes several models, listed in the table below. All transducers exhibit repeatability of better than ±0.01% full pressure scale, hysteresis of better than ±0.02% full scale and acceleration sensitivity of ±0.008% full scale /g (three axis average). Pressure resolution is better than 0.0001% and accuracy is typically 0.01% over a broad range of temperatures.

Differences between the models lie in their pressure and operating temperature ranges, as detailed below:

Further details can be found in the manufacturer's 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.

TARSAN Cruise NBP1902 CTD Data: Processing by BODC

The following parameters were supplied by the originator and mapped to BODC parameter codes:

BODC-derived Parameters

The following parameters were derived by BODC from the originator's parameters using established procedures:

Originator-derived Parameters

The following parameters were derived and supplied by the originator and have been excluded from the final dataset:

These parameters can be made available on request.

Data Processing Procedures

Following transfer the data were screened using BODC in-house visualisation software and suspect data values were assigned appropriate BODC data quality flags.

TARSAN Cruise NBP1902: Originator's CTD Data Processing

Sampling Strategy

A total of 113 CTD casts were completed during the 19/02 RV Nathaniel B. Palmer expedition (NBP1902) across the Amundsen Sea Embayment, spanning an area of approximately (67 °S, 68 °W), (75 °S, 108 °W). The bulk of the CTD operations occured in front of the Thwaites Ice Shelf and Pine Island regions. The sensors used include temperature, pressure, conductivity, oxygen, fluorescence, irradiance, altitude, and backscatter. During NBP1902, some of the casts were completed alongside moorings and autonomous underwater vehicle (AUV) deployments to act as calibrations. CTDs were deployed from 8^th February to 19^th March 2019. The deepest cast was cast 105, where the depth was recorded at 3300 m near the foot of the continental slope (-70.45217 °N, -101.96767 °E). The shallowest cast was cast 12, which descended to 200 m at the sea ice edge (-74.68717 °N, -105.84033 °E).

Initial Data Processing

Standard SeaBird Software Version Seasave V 7.26.1.8 was used for data collection and conductivity cell thermal mass correction (The SBE-11plus manufacturer recommended values were used: thermal anomaly amplitude α=0.03; thermal anomaly time constant 1/β=7.0).

Overall, data quality was good and no major malfunction of any instrument on the CTD was recorded. No obvious spikiness was found in the data.

Calibrations

Salinometry Measurements for Calibration of CTD Conductivity Sensors

Salinometer performance was poor during the sample measurements, with only 33 % of triplicate measurements agreeing to within the stated accuracy of the salinometer (± 0.003). For this reason, the salinity samples data were not used to calibrate the CTD conductivity sensor. The good salinometer data however were used to calculate the ratio of the salinometer-calculated conductivity and the CTD-measured conductivity for both the primary and secondary CTD conductivity sensors. For more details of the salinometer calibrations, please see from page 87 of the NBP1902 cruise report.

Conductivity, Temperature, and Oxygen

Calibration coefficients for conductivity, temperature, and oxygen were calculated using pre-cruise and post-cruise sensor calibrations. These were applied by the originator using standard SeaBird software. To see the calibration data and plots, please refer to the CTD calibration sheets from page 47 of the NBP1902 data distribution report.

Conductivity (SBE4):

Temperature (SBE3):

Oxygen (SBE43):

No other calibrations were applied.

Originator's Quality Control (QC) Procedure

The originator supplied the 1m vertically binned 24Hz CTD data to BODC in a single MATLAB file after applying the following QC procedures:

1. Removal of worst sensors (or merging in the case of oxygen) following post cruise calibrations.
2. Removal of up casts.
3. Removal of pre-soaks by finding the last measurement shallower than 10m on each downcast, and then removing all data up to the last point where the CTD was moving upwards (with 10-second smoothing on pressure).
4. Removal of heaves and oscillations by smoothing pressure data with a 0.5s running mean. Any periods where the CTD was moving in the opposite direction to intended with the 0.5-second smoothing (up on downcasts, and vice versa) were flagged. This is most present near the top of the water column, where less cable stretch limits natural heave compensation.
5. Removal of bad data points by aligning both temperature and both conductivity sensors using a y=ax+b linear equation (so that mean difference between both temperature sensors was 0, and same for conductivity) and then removing all data where the difference between both sensors was greater than 2x the standard deviation of the difference between both aligned sensors. A total of 13.28 % of data points were removed this way.
6. Averaging of downcasts into 1m vertical bins.

Comparison Against Independent Data Sources

Salinity, temperature, and oxygen concentration from the NBP1902 CTD measurements were compared against that from the 2010 POLARSTERN cruise ANT-XXVI/3. The deepest values for the three parameters in the Thwaites and Pine Island Bay (PIB) regions were used for verification and are as follows:

Schröder, Michael; Wisotzki, Andreas (2011). Physical oceanography measured on water bottle samples during POLARSTERN cruise ANT-XXVI/3 [dataset]. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, PANGAEA, http://doi.org/10.1594/PANGAEA.760935

Problems

Cast 74 showed low values in the primary conductivity sensor most likely linked to freezing inside the cell. The CTD was flushed and restarted. Secondary conductivity looked good.

Project Information

Thwaites-Amundsen Regional Survey and Network (TARSAN) Integrating Atmosphere-Ice-Ocean Processes affecting the Sub-Ice-Shelf Environment

TARSAN is a six year ship-based project studying how atmospheric and oceanic processes are influencing the behaviour of the Thwaites and Dotson Ice Shelves; neighbouring ice shelves which are behaving differently. The project will help identify how variations in atmospheric or oceanic conditions may influence the behaviour and stability of ice shelves in the region.

Background

Thwaites and neighbouring glaciers in the Amundsen Sea Embayment (ASE) are rapidly losing mass in response to recent climate warming and related changes in ocean circulation. Ice-sheet models suggest that the mass loss from the ASE will accelerate in the near future, initiating an eventual collapse of the West Antarctic Ice Sheet (WAIS) and raising the global sea level by up to 2.5 metres in as short as 500 years. Such model predictions, however, still lack understanding of the dominant processes within ice shelves and near grounding zones, particularly the spatial and temporal variability of these processes and their atmospheric and oceanic drivers. TARSAN (Thwaites-Amundsen Regional Survey and Network Integrating Atmosphere-Ice-Ocean Processes Affecting the Sub-Ice-Shelf Environment) is funded by US and UK funding agencies through the International Thwaites Glacier Collaboration (ITGC) to study these processes for the Thwaites and Dotson Ice Shelves.

Objectives

1. Collect the first co-temporal atmospheric, surface, englacial, and sub-ice-shelf ocean observations on Thwaites and Dotson Ice Shelves by installing automated multi-sensor stations with instrumentation on the surface, in the shelf ice, and in the ocean cavity (AMIGOS-IIIs). By connecting with undertaking AUV surveys of the cavities and firn core studies on the surface, the project can evaluate the relationship between weather/climate forcing, ice surface and basal conditions, tidal forcing, and sub-ice-shelf oceanographic flow, and extract detailed sub-iceshelf melting rate.
2. Measure repeatedly the flux of heat, freshwater and tracers (such as dissolved oxygen and noble gases) across ice-shelf fronts and assess the importance of turbulent mixing processes in altering the water mass properties entering and leaving the ice-shelf cavities; thus evaluate the dominant forcing mechanisms driving the variability in the heat flux entering the cavities.
3. Conduct the first ground-based geophysical surveys of the Eastern Thwaites and Dotson Ice Shelves, integrate with existing and new Thwaites surveys to define ice-shelf geometry, ice-shelf internal layering and basal structure (using ground-based radars); firn melt layer structure (using shallow cores and radar); sub-ice-shelf cavity geometry (using radar, active seismic profiles, and gravimetry); and determine ice flow constraints (GPS and remote sensing).
4. Provide the broader context of ice-shelf dynamics, atmospheric forcing, and ice and ocean properties (including the role of sea ice; Pettit et al., in prep) through monitoring and analysis of remote sensing data, available mooring data, ship-based multidisciplinary surveys and seal tagging throughout the length of the project.
5. Integrate and share these new observations with other related field, remote sensing, and oceanographic data through the science coordination office and through international collaborations.

Participants

The TARSAN project comprises of partners from both the UK and USA from the following institutions:

• University of East Anglia
• Oregon State University
• University of Colorado Boulder
• Temple University
• University of Alaska Fairbanks
• University of Manitoba
• St. Andrews University
• University of Rhode Island
• University of Nevada, Reno
• University of Gothenburg

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: