Metadata Report for BODC Series Reference Number 906890

• 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

RAPID Cape Farewell data quality document

Salinity showed an upward drift for the first few days in most records, which is thought to be entirely instrumental behaviour, and was deemed noisy by the originators. Care should be taken when using these data.

RAPID - Cape Farewell data quality report

Current speed values of 1.1 have been flagged suspect as this is indicative of rotor stall, a common problem with RCM7/8s. Corresponding data in the E-W and N-S velocity components have also been flagged suspect.

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

Aanderaa Recording Current Meter Model 7/8

Manufacturer's specifications: recording unit height 49.5cm (RCM8 52.0cm), diameter 12.8cm, vane size 48.5x50.0cm. Meter is designed for depths down to 2000m (RCM8 6000m). It incorporates a spindle which is shackled to the mooring line. The meter is attached to the spindle through a gimbal mounting which permits a maximum 27° deviation of the spindle from the vertical, the meter still remaining horizontal.

Meter comprises :

1. Paddle wheel rotor magnetically coupled to an electronic counter

2. Vane, which aligns instrument with current flow, has a balance weight ensuring static balance and tail fins to ensure dynamic balance in flows up to 250cm/s.

3. Magnetic compass (needle is clamped to potentiometer ring) - direction recorded with 0.35° resolution, 5° accuracy for speeds 5 to 100cm/s, 7.5° accuracy for remaining speeds within 2.5 to 200cm/s range.

4. Quartz clock, accuracy better than 2 sec/day within temperature range 0 to 20°C.

5. Thermistor (temperature sensor), standard range -2.46 to 21.48°C (max on high range 36.04°C), accuracy 0.05°C, resolution 0.1 per cent of range, 63 per cent response time 12sec.

6. Inductive cell conductivity sensor (optional), range 0 to 70mmho/cm standard resolution 0.1 per cent of range.

7. Silicon piezoresistive bridge, standard range 0 to 3000 psi (RCM8 to 9000 psi), resolution 0.1% of range.

8. Self balancing potentiometer which converts the output from each sensor into a 10 bit binary number for storage on magnetic tape.

9. Associated electronics.

A built-in clock triggers the instrument at preset intervals and up to six channels are sampled in sequence. Channel 1 is a fixed reference reading for control purposes and data identification. Channels 2, 3 and 4 represent measurement of temperature, conductivity and pressure. Channels 5 and 6 represent the VECTOR AVERAGED current speed and direction since the previous triggering of the instrument. The number of rotor revolutions and the direction is sampled every 12 seconds and broken into North and East components. Successive components are added and recorded as speed and direction. For recording intervals longer than 10 minutes, speed and direction are sampled 1/50th of recording interval.

It has become common practice in some laboratories to deploy these meters as temperature and conductivity loggers without current measuring capabilities.

The following link will provide the manufacturer specifications:

RAPID - Cape Farewell current meter data processing notes

This document outlines the procedures undertaken to process and quality assure current meter data collected to the east of Cape Farewell, Greenland, as part of the RAPID programme.

Originator's processing

The raw data are downloaded from the instrument and converted to ASCII format. The data are then converted to PSTAR format.

Calculating calibration coefficients

Manufacturers calibrations are applied to the current speed and direction channels.

Two sets of calibration coefficients were employed in the calibration of the pressure, temperature and conductivity data. The first set was obtained either from the manufacturer's calibration coefficients or from the calibration laboratory at the National Oceanography Centre, Southampton (NOCS), hereinafter called laboratory calibrations. The second set, called in-situ calibrations, was obtained by a comparison with CTD data taken on cruise D309. The current meters were strapped to the CTD frame and a full depth CTD cast performed. CTD data obtained during the cast bottle stops were compared to that from the current meter and coefficients derived by fitting a cubic polynomial to the data of the form:

y = A + Bx + Cx² + Dx³

where A,B,C,D are the coefficients, x is the uncalibrated data and y is the calibrated data.

Both sets of calibration coefficients were employed in converting raw data to physical measurements. Where available, the in-situ temperature and conductivity coefficients were deemed superior as they provided a homogeneous data set.

Data processing

During the conversion from ASCII to PSTAR format the data are calibrated and corrected for magnetic variation. Current velocity components are then derived. Salinity is calculated using the in-situ temperature and conductivity data where available. The pressure for the salinity calculation is chosen on a per instrument basis and is whichever of the two calibration sets that most closely agree with the planned instrument depth/pressure.

The Aanderaa RCM7/8 instruments recorded data throughout each hour (20 samples at 3 minute intervals). Therefore the timestamp of the measurement was selected to be the mid-hour mark. The Aanderaa RCM11 instruments record a burst of measurements just before each hour and each half hour and these were the times assigned to the data measurements.

Quality control

Data were visually inspected for out-lying data and instrument electrical spikes removed.

BODC processing

Data are received after quality checks have been made and calibrations have been applied. The data files are submitted in PSTAR format as one file per instrument.

Once the submitted data files are safely archived, the data undergo standard reformatting and banking procedures:

• The data files are reformatted into a common format, a NetCDF subset.
• Standard parameter codes are assigned that accurately describe the data (see parameter rationalisation and mapping section below).
• Unit conversions are applied, if necessary, so that units are standardised (see parameter rationalisation and mapping section below).
• The data are screened visually and any spikes or instrument malfunctions can be clearly labelled with quality control flags.
• Comprehensive documentation is prepared describing the collection, processing and quality of each data series.
• Detailed metadata and documents are loaded to the database and linked to each series so that the information is readily available to future users.

The following is a summary of what calibrations (laboratory and in-situ) were supplied in which series.

*Only contained laboratory calibrated temperature and pressure.

Parameter rationalisation and mapping

The originator expressed a preference for in-situ over laboratory calibrated channels, so where both in-situ and laboratory calibrated channels were present, the laboratory calibrated channels were dropped from the series. Where in-situ calibrated channels were not available, the laboratory calibrated channels were retained.

The following describes the parameters contained in the series and their mapping to BODC parameter codes. Some parameters e.g. current velocities, were not supplied in every file. Where not supplied and applicable, these channels were calculated by BODC. See parameter derivation section below.

Parameter derivation

The following describes the parameters derived by BODC and their mapping to BODC parameter codes. These parameters were only derived by BODC if they were not supplied by the originators.

Project Information

Rapid Climate Change (RAPID) Programme

Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council (NERC). The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

Scientific Objectives

• To establish a pre-operational prototype system to continuously observe the strength and structure of the Atlantic Meridional Overturning Circulation (MOC).
• To support long-term direct observations of water, heat, salt, and ice transports at critical locations in the northern North Atlantic, to quantify the atmospheric and other (e.g. river run-off, ice sheet discharge) forcing of these transports, and to perform process studies of ocean mixing at northern high latitudes.
• To construct well-calibrated and time-resolved palaeo data records of past climate change, including error estimates, with a particular emphasis on the quantification of the timing and magnitude of rapid change at annual to centennial time-scales.
• To develop and use high-resolution physical models to synthesise observational data.
• To apply a hierarchy of modelling approaches to understand the processes that connect changes in ocean convection and its atmospheric forcing to the large-scale transports relevant to the modulation of climate.
• To understand, using model experimentation and data (palaeo and present day), the atmosphere's response to large changes in Atlantic northward heat transport, in particular changes in storm tracks, storm frequency, storm strengths, and energy and moisture transports.
• To use both instrumental and palaeo data for the quantitative testing of models' abilities to reproduce climate variability and rapid changes on annual to centennial time-scales. To explore the extent to which these data can provide direct information about the thermohaline circulation (THC) and other possible rapid changes in the climate system and their impact.
• To quantify the probability and magnitude of potential future rapid climate change, and the uncertainties in these estimates.

Projects

Overall 38 projects have been funded by the RAPID programme. These include 4 which focus on Monitoring the Meridional Overturning Circulation (MOC), and 5 international projects jointly funded by the Netherlands Organisation for Scientific Research, the Research Council of Norway and NERC.

The RAPID effort to design a system to continuously monitor the strength and structure of the North Atlantic Meridional Overturning Circulation is being matched by comparative funding from the US National Science Foundation (NSF) for collaborative projects reviewed jointly with the NERC proposals. Three projects were funded by NSF.

A proportion of RAPID funding as been made available for Small and Medium Sized Enterprises (SMEs) as part of NERC's Small Business Research Initiative (SBRI). The SBRI aims to stimulate innovation in the economy by encouraging more high-tech small firms to start up or to develop new research capacities. As a result 4 projects have been funded.

RAPID - Cape Farewell and Eirik Ridge: Interannual to Millennial Thermohaline Circulation Variability

This project was funded under the NERC Rapid Climate Change Programme, grant number NER/T/S/2002/00453. Dr. Sheldon Bacon (Southampton Oceanography Centre) was the Principal Investigator, with co-Investigators from the University of Southampton, Prof. D. A. Stow and Dr. E. J. Rohling. The project started in December 2003 and ended in November 2008.

The project used a combination of hydrography and palaeoceanography measurements to determine the spectrum of variability of the Deep Western Boundary Current, on timescales from days to millennia. The project focused on deglacial to Holocene variability; in particular, seeking to characterise the onset and endings of three cold periods: the Younger Dryas (YD; 12.5-11.5 ka BP), the ~8.2 ka event, and the Little Ice Age (LIA; 16th-19th century AD).

The objectives of the project included:

• Defining the THC response to Holocene climate variability by a highly resolved investigation of palaeoceanographic/climate proxies in sediment cores
• Developing high-resolution sediment proxies for bottom current speed
• Absolute calibration of sediment proxies for bottom current speed
• Defining the relationship between drift construction and the bottom current regime
• Improved definition of present-day ocean circulation and climate

Most of the fieldwork was carried out on 2 cruises in the Cape Farewell and Irminger Sea vicinity:

Data Activity or Cruise Information

Data Activity

RAPID Moored Instrument Rig SB_LM_A#1

This rig was deployed as part of the current meter array to the east of Cape Farewell, Greenland, a component of the RAPID programme.

The rig was anchored by 1200 kg of steel chain bundled together with 5/8" galvanised long link chain. Buoyancy was provided by 17 inch glass spheres attached to the mooring line in groups over the height of the mooring and a 48 inch steel sphere attached at the top of the mooring.

Instruments deployed on the rig

*These instruments belong to IFREMER

Related Data Activity activities are detailed in Appendix 1

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:

Appendix 1: SB_LM_A#1

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.