Metadata Report for BODC Series Reference Number 1792152

• 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.

Instrument Description for JR20080221 (JR179)

CTD Unit and Auxiliary Sensors

The CTD unit comprised a Sea-Bird Electronics (SBE) 9 plus underwater unit, an SBE 11 plus deck unit, a 12-way SBE 32 carousel and 12 10 L Water Samplers. Attached to the CTD were two SBE 3P temperature sensors, two SBE 4C conductivity sensors, one Paroscientific Digiquartz pressure sensor, one SBE 43 dissolved oxygen sensor, one Biosperical PAR sensor, one Tritech Altimeter, one Chelsea Aquatracka MKIII fluorometer and one Chelsea Alphatracka MKII transmissometer.

The altimeter failed on the first CTD deployment but worked for all subsequent casts. The SBE35 temperature sensor failed to take readings for a number of bottle firings for casts 12, 13, 14, 15, 18 and 19.

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.

SeaBird SBE35 Deep Ocean Standards Thermometer

The SBE 35 is a high precision thermometer that can be used in fixed point cells or at depths up to 6800 m. It is not affected by shock and vibration, allowing it to be used in calibration laboratories and for thermodynamic measurement of hydro turbine efficiency.

The SBE35 can be used with the SBE32 Carousel Water Sampler and with a real-time or autonomous CTD system. In this case, an SBE35 temperature measurement is collected each time a bottle is fired and the value is stored in EEPROM (Electrically Erasable Programmable Read-Only Memory), eliminating the need for reversing thermometers while providing a high accuracy temperature reading.

The SBE35 is standardized in water triple point (0.0100 °C) and gallium melting point (29.7646 °C) cells, following the methodology applied to the Standard-Grade Platinum Resistance Thermometer (SPRT). However, it does not need a resistance bridge, making it more cost-efficient than an SPRT.

Temperature is determined by applying an AC excitation to reference resistances and an ultrastable aged thermistor. Each of the resulting outputs is digitized by a 20-bit A/D converter. The AC excitation and ratiometric comparison uses a common processing channel, which removes measurement errors due to parasitic thermocouples, offset voltages, leakage currents and gain errors.

Specifications

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

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 Log Quantum Cosine Irradiance Sensor QCD-905L

The QCD-905L is a submersible radiometer designed to measure irradiance over Photosynthetically Active Radiation (PAR) wavelengths (400-700 nm). It features a cosine directional response when fully immersed in water.

The sensor is a blue-enhanced high stability silicon photovoltaic detector with dielectric and absorbing glass filter assembly, and produces a logarithmic output. Normal output range is -1 to 6 volts with 1 volt per decade. Typically, the instrument outputs 5 volts for full sunlight and has a minimum output of 0.001% full sunlight, where typical noon solar irradiance is 1.5 to 2 x 10¹⁷ quanta cm^-2 s^-1. The instrument can be calibrated with constants for µE cm^-2 s^-1 or quanta cm^-2 s^-1.

The QCD-905L can be coupled to a fixed range data acquisition system like a CTD (Conductivity-Temperature-Depth) profiler or current meter. It has an aluminium and PET housing, and a depth rating of 7000 m.

Specifications

Further details can be found in the manufacturer's manual.

Tritech Digital Precision Altimeter PA200

This altimeter is a sonar ranging device that gives the height above the sea bed when mounted vertically. When mounted in any other attitude the sensor provides a subsea distance. It can be configured to operate on its own or under control from an external unit and can be supplied with simultaneous analogue and digital outputs, allowing them to interface to PC devices, data loggers, telemetry systems and multiplexers.

These instruments can be supplied with different housings, stainless steel, plastic and aluminum, which will limit the depth rating. There are three models available: the PA200-20S, PA200-10L and the PA500-6S, whose transducer options differ slightly.

Specifications

Common specifications are presented below

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

Originator's processing document for RRS James Clark Ross JR20080221 (JR179) CTD data

Sampling strategy

A total of 24 CTD casts were performed during JR20080221 (JR179), which sailed from Stanley, Falkland Islands on 21 February 2008 and docked in Stanley, Falkland Islands on 11 April 2008. The main objectives for this cruise were to perform biological studies and marine geological and geophysical investigations in the Amundsen and Bellinghausen Seas.

Data processing

For each cast the following raw data files were generated:

• jr179_NNN.dat- raw data
• jr1179_NNN.hex- raw data
• jr1179_NNN.con- configuration
• jr1179_NNN.hdr- header
• jr1179_NNN.bl- bottle

where NNN is the cast number for the CTD data series. The data were not processed by the originator.

Processing by BODC of RRS James Clark Ross JR20080221 (JR179) CTD data

Raw data were submitted to BODC in the form of SeaBird format. The following procedures were applied using the SBE Data Processing software (Version 7.23.2):

• DatCnv was used to read in the raw CTD data file (.hex) which contained the data in engineering units and apply calibrations as appropriate through the instrument configurations (.con) file
• Bottle summary was run for all files and a .btl file with the average, standard deviation, min and max values recorded by the CTD instrument suite at bottle firings was created
• Filter was run on the pressure channel to smooth out the high frequency data
• AlignCTD was used to advance the oxygen data by 8 seconds
• CellTM was run using alpha = 0.03 and 1/beta = 7, to correct for conductivity errors induced by the transfer of heat from the conductivity cell to the seawater
• Section and Loopedit were used to identify and remove the surface soak
• Derive was run to create the variables Salinity, Salinity 2 and Oxygen SBE 43
• BinAverage and Strip were run to average the data to 2Hz bins (0.5 seconds) and to remove the salinity and oxygen channels which were created when Derive was run

No further processing or calibrations were applied to these data. The final files in .cnv format were then transferred into BODC's internal NetCDF format and original variables were mapped to the appropiate BODC codes, as follows:

The reformatted data were visualised using the in-house EDSERPLO software. Suspect 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.

Data from the secondary Temperature, Salinity and Conductivity sensors were also transferred but dropped following screening as there was no difference between the quality between the primary and secondary sensors. These channels as well as the derived parameters that were calculated from them are available upon request.

Project Information

Glacial Retreat in Antarctica and Deglaciation of the Earth System (GRADES)

Introduction

GRADES was designed to investigate the state and stability of the Antarctic ice sheet, and its results will contribute to a better prediction of how the WAIS contributes to sea level rise.

Throughout the project ice-sheet models will be developed and tested using newly acquired ice-sheets histories. These models will use satellite data, reconstruct ions of past states of the ice sheet and new data assimilation techniques.

This project has three components:

• IMAGE: Inverse Modelling of Antarctica and Global Eustasy
• TIGRIS: TargetIngs Glacial Retreat and Ice-stream Systems
• QWAD: Quaternary West Antarctic Deglaciations

GRADES has links to other BAS programs like GEACEP, CACHE, ACES and COMPLEXITY.

Objectives:

• Understand the role of ice sheet disintegration in global climate change
• Assess what is causing the current imbalance in the WAIS
• Search for evidence of previous periods of rapid ice loss in the WAIS
• Determine the contribution of the WAIS to future sea level change

Data Availability

The data produced during this project are available to the academic community.

Acronyms used in the text:

• WAIS- West Antarctic Ice Sheet
• GEACEP- Greenhouse to ice-house: Evolution of the Antarctic Cryosphere and Palaeoenvironment
• CACHE- Climate and Chemistry: forcings , feedbacks and phasings in the Earth System
• ACES- Antarctic Climate and the Earth System
• COMPLEXITY- Natural Complexity Programme

Quaternary West Antarctic Deglaciation (QWAD)

Introduction

QWAD is one of the projects comprised by GRADES. It was created to integrate high-resolution marine studies with onshore records of deglaciation, provided by studies of past sea level changes, and dating of the times at which mountain peaks became exposed due to thinning of the ice sheet.

The methods involve advanced radiocarbon and cosmogenic dating technics and also modelling. This project has links to GRADES-IMAGE but will also use data collated in the BAS-led Antarctic glacio-geological database.

Objectives:

The main objectives include the investigation of five aspects of deglaciation:

• the baseline- how large was the glacial maximum ice sheet?
• thinning of the ice sheet recorded by formerly buried and/or eroded rock outcrop
• retreat of the ice sheet, recorded by marine sediments
• relative sea level change at the periphery of the ice sheet, recording the response to glacial unloading and global sea level change
• evidence for previous collapse of the ice sheet during the paste few hundred thousand years

Another objective is the production of an unified history of glacial retreat in the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula Ice Sheet (PAIS).

Data Restrictions

Data obtained on this project are available to BAS staff.

Global Science in an Antarctic Context (GSAC)

Introduction

GSAC is the British Antarctic Survey research programme from 2005 to 2009, it encompasses 8 programmes, including 18 projects as well as long-term monitoring and survey activities.

This programme was created to fulfill BAS vision of becoming, by 2012, the leading international centre making use of the of the Antarctic and the Southern Ocean. This research programme consists of an integrated set of inter-disciplinary research, monitoring and survey activities designed to extract new knowledge from the Antarctic, provide information to policy makers and benefit society in general.

GSAC supports the Natural Environment Research Council (NERC) strategy Science for a Sustainable Future and contributes to other programmes such as the World Climate Research programme, the International Geosphere-Biosphere Programme, the Convention on Biological Diversity, the Scientific Committee for Antarctic Research and the International Polar Year 2007-2009.

The programme's components are highly interconnected and its content makes full use of BAS Antarctic infrastructure and builds on previous BAS research, survey and monitoring, whilst also exploring new areas.

The programmes contributing to GSAC are:

• ACES- Antarctic Climate and the Earth System
• BIOFLAME- Biodiversity, Function, limits and Adaptation from Molecules to Ecosystems
• CACHE- Climate and Chemistry: Forcings, Feedbacks and Phasings in the Earth System
• COMPLEXITY- Natural Complexity Programme
• DISCOVERY 2010- Integrating Southern Ocean Ecosystems into the Earth System
• GEACEP- Greenhouse to Ice-House Evolution of the Antarctic Cryosphere and Paleoenvironment
• GRADES- Glacial Retreat in Antarctica and Deglatiation of the Earth System
• SEC- Sun Earth Connections
• LTMS- Long Term Monitoring and Survey

More detail is provided in each programme document.

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: