Metadata Report for BODC Series Reference Number 1787021

• 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

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 Nortek Aquadopp data were supplied to BODC as ASCII files and converted to BODC internal format (QXF).

During transfer the originator's variables were mapped to unique BODC parameter codes. The following table shows the parameter mapping.

Following transfer the data were screened using BODC in-house visualisation software. Suspect data values were assigned the appropriate BODC data quality flag. Missing data values, where present, were changed to the missing data value and assigned a BODC data quality flag.

Originator's Data Processing

Sampling strategy

Data were collected from multiple Nortek Aquadopp current meters fitted on three moorings across the Rockall Trough. Details are displayed in the table below.

The moorings were deployed to the seabed from an acoustic release as part of cruise PE399. The Aquadopp instruments were fixed at various depths on the mooring to collect measurements of temperature, pressure, velocity, heading, pitch and roll every 30 minutes. They were recovered as part of cruise DY053.

Data processing

Raw instrument data were downloaded from the instrument after the recovery of the mooring. The data are stored by mooring name ready for processing. The files along with the mooring information underwent processing to remove the launching and recovery period and prepare them into ASCII files ready for submission to BODC. Further information can be found in the cruise report.

Project Information

UK - Overturning in the Subpolar North Atlantic Programme (UK-OSNAP) Programme

UK-OSNAP is part of an international collaboration to establish a transoceanic observing system in the subpolar North Atlantic. The aim is to quantify and understand the Subpolar Gyre's response to local and remote forcing of mass, heat and freshwater fluxes, within the conceptual framework of the Atlantic Meridional Overturning Circulation (AMOC).

UK-OSNAP is developing a new observing system to provide a continuous record of full-depth, trans-basin mass, heat, and freshwater fluxes. Combining these sustained measurements with innovative modelling techniques will enable the project to characterise the circulation and fluxes of the North Atlantic Subpolar Gyre.

UK-OSNAP is funded by the Natural Environment Research Council (NERC). The project is led by the National Oceanography Centre (NOC) with partners in the University of Liverpool, the University of Oxford and the Scottish Association for Marine Science (SAMS). It is a part of international OSNAP that is led by USA and includes 10 further partner groups in Canada, France, Germany, the Netherlands and China. The project involves fieldwork at sea and model studies.

The OSNAP observing system consists of two legs: one extending from southern Labrador to the southwestern tip of Greenland across the mouth of the Labrador Sea (OSNAP West), and the second from the southeastern tip of Greenland to Scotland (OSNAP East). The observing system also includes subsurface floats (OSNAP Floats) in order to trace the pathways of overflow waters in the basin and to assess the connectivity of currents crossing the OSNAP line.

NERC have added an extension to UK-OSNAP, until October 2024. This will result in the UK-OSNAP-Decade: 10 years of observing and understanding the overturning circulation in the subpolar North Atlantic (2014-2024).

Data Activity or Cruise Information

Data Activity

OSNAP Moored Instrument WB1 2015-2016

This rig was deployed as part of the Rockall Trough array of the "Overturning in the subpolar North Atlantic Programme" (OSNAP).

The rig was held down by a 1600 kilogram anchor on the seabed at 1600 metres depth. It was kept a erect by a 40" syntactic float at 488 metres depth and a 31" syntactic float at 242 metres depth.

The instruments deployed on the rig were as follows:

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

UK-OSNAP/Ellett Array Mooring RTWB1 (OM55)

Mooring RTWB1 (called OM55 by the International OSNAP Community) forms part of the OSNAP-East Transect and, from 2018, the Ellett Array. It was first deployed on 17^th July 2014 by the UK-OSNAP Community.

It is located at 57.4707°N, 12.7050°W where there is a water depth of 1600m

Between 2014 and 2018 this mooring was funded by UK-OSNAP, from 2018 it was funded as part of the Ellett Array by CLASS (Climate Linked Atlantic Sector Science).

Related Fixed Station activities are detailed in Appendix 2

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: RTWB1_02_2015

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.

Appendix 2: UK-OSNAP/Ellett Array Mooring RTWB1 (OM55)

Related series for this Fixed Station 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.