Metadata Report for BODC Series Reference Number 1763368

• 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 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

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.

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.

BODC Processing - Autosub data

Data were received by BODC in Matlab files, with one file containing all data from the Autosub missions. The data were reformatted to QXF (a NetCDF file format) by in house software. A separate QXF file was created for data from each data type from each mission. Metadata were also extracted from the originator's file and used to populate the BODC database.

The following tables shows how the variables within the files were mapped to appropriate BODC parameter codes for each of the data types supplied:

CTD data

Ice draft data

Seabed depth data

Quality control

Following transfer to QXF, the data were quality controlled using BODC's in-house visualisation software.

Originator's processing - Autosub data

Data collection

Autosub missions were completed during Nathaniel B Palmer cruise NBP09-01 (January 2009) in the Amundsen Sea near the Pine Island Glacier. The data were collected for the Natural Envrironment Research Council funded Ocean Circulation and Ice Shelf Melting on the Amundsen Sea Continental Shelf project (NE/G001367/1).The Autosub was equipped with the following instrumentation: Seabird 9+ CTD, with dual conductivity and temperature sensors plus a SBE43 dissolved oxygen sensor and Wetlabs transmissometer; Simrad EM2000 multi-beam echosounder; upward-looking RDI 300 kHz ADCP; downwardlooking RDI 150 kHz ADCP.

For more information about the Autosub missions and data collection see the cruise report

Data processing

The data collected were processed by the originator and the CTD data plus geometry data (ice draft and sea bed depth) from the ADCP ranges were supplied to BODC.

For information about the Autosub data processing see the cruise report

Project Information

Ocean Circulation and Ice Shelf Melting on the Amundsen Sea Continental Shelf

Background and objectives

The Ocean Circulation and Ice Shelf Melting on the Amundsen Sea Continental Shelf is a NERC funded project designed to understand what is happening to the Antarctic Ice Sheet. The Pine Island Glacier is the main focus of this project and it represents one of the ice sheets where the fastest changes are happening. Despite seeing the signs of these changes, scientists have yet to uncover what is causing them.

Data collection techniques involve the use of a robotic submarine capable of navigating beneath the ice, make measurements along a pre-defined track and return to the surface where data transmission/retrieval occurs. Data collected from these missions will be used to build a computer model that describes the flow of water within the remote cavern beneath glacier and in the sea to the north of it. Using this model we will determine if there have been any changes in the water temperature in Pine Island Bay over the past 20 years and how such changes would have affected melting of the glacier base. The results can then be used by other scientists to establish if changes in the glacier's melt rate could have caused the ice sheet to thin in the way that has been observed, and there will be a greater certainty when stating what impact the glaciers of Pine Island Bay will have on the future coastlines of Holland and East Anglia.

Participants

This project is coordinated by the British Antarctic Survey (BAS) on behalf of NERC and carried out in collaboration with American scientists (funded by the National Science Foundation). Data collection activities took place on board the Nathaniel B. Plamer, operated by the Antarctic Support Contract on a long-term charter from Edison Chouest Offshore, but with isntrumentation owned by BAS.

Fieldwork and data collection

Deployment of an Autosub3 AUV allowed for data collection within a pre-programmed track while navigating by dead reckoning relative to the seabed or the ice-shelf base.

Data management

Data management for the autosub data will be done by the British Oceanographic Data Centre whilst other ice data will be managed by the Polar Data Centre.

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: