Metadata Report for BODC Series Reference Number 1790330

• 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 JR20070226 (JR165, JR170, JR174)

CTD Unit and Auxiliary Sensors

REVIEW

The CTD unit comprised a Sea-Bird Electronics (SBE) 9 plus underwater unit, an SBE 11 plus deck unit, an SBE 32 carousel. Attached to the CTD were two SBE 3P temperature sensors, two SBE 4C conductivity sensors, one Paroscientific Digiquartz pressure sensor, two SBE 43 dissolved oxygen sensor, one Altimeter, one CTG Aquatracka MKIII fluorometer and one Transmissometer.

No information (Make, Model, Serial number, Last calibration date) could be found for the Altimeter.

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.

Originator's processing document for RRS James Clark Ross JR20070226 (JR165, JR170, JR174) CTD data

Sampling strategy

A total of 254 CTD casts were performed during JR20070226 (JR165, JR170, JR174), which sailed from Stanley, Falkland Islands on 26 February 2007 and docked in Stanley, Falkland Islands on 16 April 2007. The main objective for this cruise was recover a mooring deployed in Ryder Bay, off Rothera Research Station.

Data processing

For each cast the following raw data files were generated:

• jr165_NNN.dat- raw data
• jr165_NNN.hex- raw data
• jr165_NNN.con- configuration
• jr165_NNN.hdr- header
• jr165_NNN.bl- bottle

where NNN is the cast number for the CTD data series. The originator partially processed the data but it was found that oxygen had not been selected during the procedures. Therefore it was decided to process the data from raw at BODC (originator's initial steps were identical to the ones used at BODC).

Processing by BODC of RRS James Clark Ross JR20070226 (JR165, JR170, JR174) CTD data

Partially processed data were submitted to BODC, however upon inspection it was found that the oxygen voltages had not been selected during the orginator's procedures. As BODC procedures were similar to the ones applied by the originator, it was decided to re-process the data from the raw files and finalise the procedures by creating files 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:

Data from the secondary Temperature, Salinity, Conductivity and Oxygen 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.

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.

For series 1789710, 1789722 and 1789734 the secondary temperature channel did not record valid data. No secondary oxygen data was recorded for series 1791634, 1791646, 1791658, 1791671, 1791683, 1791695, 1791702, 1791714, 1791726, 1791738, 1791751, 1791763, 1791775, 1791787, 1791799 1791806, 1791818, 1791831, 1791843, 1791855.

Project Information

ACES- Antarctic Climate and the Earth System

Introduction

This project is part of the BAS GSAC five year research programme. It was funded by NERC and extended from 2005 to 2009.

ACES aims to investigate the atmospheric and oceanic links that connect the climate of the Antarctic to that of lower latitudes, and their controlling mechanisms. Specific research topics include the formation and properties of Antarctic clouds, the complexities of the atmospheric boundary layer and the importance to the global ocean circulation of cold, dense water masses generated in the Antarctic.

Data will be collected by a comprehensive programme of oceanographic measurements from BAS ships in the Weddell and Bellingshausen Seas and by the Twin Otter aircraft, which will allow for the study of cloud microphysics and air-sea-ice interaction. An ice core will be collected from the southwestern Antarctic Peninsula and will give a 150-year record of the strength of the circumpolar westerly winds. This data will be used to test and improve global climate models and a new regional atmosphere-ice-ocean model for the Antarctic.

ACES has two components: ACES-FOCAS (Forcings from the Ocean, Clouds, Atmosphere and Sea-ice) and ACES-ACCENT (Antarctic Climate Change and Nonlinear Teleconnections). It also links with several other projects: CACHE, GRADES, GEACEP, BIOFLAME, DISCOVERY2010 and SEC.

Scientific Objectives

The main objectives are:

• Understand the interactions between atmosphere, sea-ice and ocean at high southern latitudes
• Develop models to aid our understanding of Antarctic regional processes and enable the representation of essential regional phenomena in global models covering both the atmosphere and ocean
• Determine the nature and influence of the principal connections between Antarctica and the global climate system
• Determine the importance of water masses of Antarctic origin in the global ocean circulation
• Determine the sensitivity of the global climate system to processes occurring or originating in the Antarctic

Data Availability

Data sets collected during this project are available to the academic community.

Acronyms used in this text:

BAS- British Antarctic Survey

GSAC- Global Science in an Antarctic Context

CACHE- Climate and Chemistry: forcings , feedbacks and phasings in the Earth System

GRADES- Glacial retreat in Antarctica and Deglaciation of the Earth System

GEACEP- Greenhouse to ice-house: Evolution of the Antarctic Cryosphere and Paleoenvironment

BIOFLAME- Biodiversity, Function, Limits and Adaptation from Molecules to Ecosystems

DISCOVERY2010- Integrating Southern Ocean Ecosystems into the Earth System

SEC- Sun Earth Connections Programme

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: