Metadata Report for BODC Series Reference Number 1208561

• 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 Quality Report

There is evidence of mooring 'knockdown' between 23rd November and 29th November 2008. This has mostly affected the Nortek_1415 instrument on Mooring 3, this has not been flagged.

The heading channel for all instruments and moorings is suspect towards the end, these have been flagged as such.

The sampling interval increased and became more variable for the Nortek_1420 on Mooring 3 after 21st November 2008 16:44:00. There are large jumps in time and data between 23rd November and 3rd December 2008, data values between these have been flagged as suspect. There is also very little reliable conductivity or salinity data for this instrument.

Data Access Policy

Public domain 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.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

Nortek Aquadopp Open Water Current Meter

This instrument provides 3D acoustic doppler current measurements along with standard measurements of temperature, pressure, tilt and direction. It can be used in real time measurement situations or can log to an internal recorder powered by internal batteries. It can also be configured to measure surface wave height, period and direction concurrently. It has the unique feature of being run in 'diagnostic' mode when set to collect data at 1 Hz frequency in user specified intervals. This allows studies of mooring motion and the performance of other current meters to be conducted. It can be set in various configurations with titanium housings for deployment at greater depths.

Standard Measured Parameters

• 3D current velocity (East/North/Up, X/Y/Z or Beam 1/2/3)

• Acoustic signal strength (Beam 1/2/3)

• Compass

• Tilt

• Temperature

• Pressure

• Battery voltage

• Status code

• Error code

Surface wave monitoring

The standard Aquadopp is suitable for measuring surface wave height, period, and direction, which are calculated using the PUV method whereby spectra are estimated based on a combination of the pressure signal recorded by the instrument (P) and two horizontal components of the wave orbital velocity (U and V). More specifically, the pressure signal is used to provide an estimate of the wave frequency spectrum. The energy in this spectrum is then used to estimate wave height and period. The measurements of the wave orbital velocities are used to provide an estimate of the wave direction. Since these estimates are based on the distribution of wave energy and are not direct measurements of the free surface, they should be considered inferred estimates.

Both the dynamic pressure and the orbital velocities are driven by surface waves. The signals that are associated with these properties are complicated by the fact that they attenuate (that is the signals are weaker) with depth. The exact behaviour of the attenuation is determined by the water depth and the wavelength being observed. The greater the water depth the greater the attenuation; likewise, the shorter the wavelength (or higher the frequency of the wave) the greater the attenuation for a given water depth. This means that the estimation of wave parameters is limited by both water depth and wave frequency.

Specifications

Further details can be found in the manufacturer's specification sheets for the Aquadopp, Aquadopp 3000 and Aquadopp 6000.

BODC Processing

The data were received in four Matlab format files one for each instrument. The received data were converted into BODC internal format following BODC's standard procedures. The table below shows how the variables within the Matlab file were mapped to appropriate BODC parameter codes. In addition to these, time, datenum, error_code, status_code, analog_input1, battery_voltage, amplitude_beam1_east, amplitude_beam2_north and amplitude_beam3_up accompanied the data but were not transferred.

All reformatted data were visualised using the in-house Edserplo software. Suspect and missing data were marked by adding an appropriate quality control flag.

References

Fofonoff, NP and Millard, RC. 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science, 44, p.53.

Originator's Processing

Data from four Nortek Aquadopp current meters were collected on two moorings deployed during the SOFINE cruise JC029. One deployed on the Northern UK Mooring 2 and three deployed on the Central UK Mooring 3. On recovery it was found that the frames of all Nortek Aquadopps current meters looked stretched. During the cruise the data were downloaded and processed into physical units. The downloaded data were inspected for completeness and data quality. As part of this process, data from the instrument were stored in the form of a Matlab structure. During downloading of the Nortek Aquadopps data, two of the instruments (1415 and 1430) produced an error regarding missing two records.

Project Information

Southern Ocean FINEStructure (SOFINE) project document

The Southern Ocean FINEStructure (SOFINE) project was a UK field programme aimed at studying the frictional processes that slow down the Antarctic Circumpolar Current (ACC) and influence the meridional exchange of water masses in the Southern Ocean.

The study investigated the role of sea floor topography in slowing the ACC and driving meridional flow across the Southern Ocean, and the manner in which mesoscale and small scale oceanic phenomena modified water mass properties and affected their movement across the ACC. Specifically, SOFINE set out to:

• Determine the relative importance of oceanic processes associated with large scale (hundreds to thousands of kilometres) and small scale (a few kilometres) sea floor topography in the context of ACC flow rates and water mass exchange.
• Identify the oceanic processes controlling the rate at which water masses are transformed and fluxed across the ACC.

The SOFINE experiment focused on a major meander of the ACC around the northern Kerguelen Plateau in the Indian Ocean. Theories and models of Southern Ocean circulation indicated that this region experienced intensified 'friction' and cross-ACC flow. Fieldwork was undertaken over a 52 day period in November and December 2008, and included hydrographic observations, microcstructure and turbulence measurements, detailed bathymetric surveys and several deployments of floats, drifters and moorings.

SOFINE was funded by the UK Natural Environment Research Council and involved the collaboration of a number of international institutions: the National Oceanography Centre (UK), the University of East Anglia (UK), British Antarctic Survey (UK), Woods Hole Oceanographic Institution (US), the Commonwealth Scientific and Industrial Research Organisation (Australia), the University of Tasmania (Australia) and the Leibniz Institute of Marine Sciences (IFM-GEOMAR) at the University of Kiel (Germany).

For more information please see the official project website at SOFINE

Data Activity or Cruise Information

Data Activity

SOFINE JC029 Short-term Moored Instrument Northern Mooring 2

Prior to the mooring operations, a 12 hour swath survey was completed of a ridge that extended northward from the Kerguelen Plateau between -46° 30' S to -47° S and 71° 45' E to 72° E. Locations of the mooring sites were then determined from the swath data. Three short-term moorings were deployed located within approximately 1 km of each other. All moorings were deployed using a National Oceanography Centre Southampton (NOCS) double barrel winch (electro-hydraulic) and reeling winch system which was load tested prior to commencement of operations. The moorings were deployed 'top first - anchor last', allowing the buoyancy to stream away from the vessel during deployment. The ship's speed varied between 0.3 and 1.2 knots during the mooring deployment. The anchors for the three UK moorings consisted of a 550 kg mushroom anchor and 2200 kg of eight inch chain. This was designed to be deployed such that as it reached the seabed the mushroom anchor would land first, and the chain would land on the seabed to provide as much scope and drag as possible due to the anticipated high energies.

The mooring location was determined from three independent ranging locations (triangulation) to the acoustic release. The ship was positioned approximately an ocean depth horizontally away from the likely location of the mooring. A transducer was deployed over the side of the ship and the slant range (distance) to the mooring was obtained. The calculated horizontal distance provided an estimate of the radius from the ship location within which the mooring was located. The cross-over of the three range circles ("cocked hat") provided an estimate of the location of the mooring.

Instruments deployed on the rig

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: MOOR2

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.