Metadata Report for BODC Series Reference Number 1097498

• 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

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.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

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 Current Meter Screening

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

• Irregularities such as unfeasible values
• Inconsistencies between related information. For example:
  • Depths of meter and sea bed.
  • Times for mooring deployment and for start/end of data series.
  • Length of record or number of data cycles, the cycle interval, the clock error and the period over which accrued.
  • Parameters stated as measured and the parameters actually present in the data cycles.
• Originator's comments on meter/mooring performance and data quality.

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non- oceanographic origin may be tagged with the BODC flag denoting suspect value.

The following types of irregularity, each relying on visual detection in the time series plot, are amongst those which may be flagged as suspect:

• Spurious data at the start or end of the record.
• Obvious spikes occurring in periods free from meteorological disturbance.
• A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities, deemed abnormal, then instead of flagging the individual suspect values, a caution may be documented. Likewise documents will highlight irregularities seen in the current vector scatter plots such as incongruous centre holes, evidence of mooring 'knock-down', abnormal asymmetry in tidally dominated records or gaps as when a range of speeds or directions go unregistered due to meter malfunction.

The term 'knock-down' refers to the situation when the 'drag' exerted on a mooring at high current speeds may cause instruments to tilt beyond the angle at which they are intended to operate. At this point the efficiency of the current sensors to accurately record the flow is reduced.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought, and where necessary, documented. This covers inconsistencies in the following:

• Maximum and minimum values of parameters (spikes excluded).
• The orientation and symmetry of the current vector scatter plot.
• The direction of rotation of the current vectors.
• The approximate amplitude and periodicity of the tidal currents.
• The occurrence of meteorological events and, finally, for series for which no time check was possible, the phase.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

RAPIDMOC/MOCHA Current Meter data processing document

This document outlines the procedures undertaken to process and quality assure current meter data collected under the RAPIDMOC and MOCHA projects.

Originator's processing

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

Once in ASCII format the data are corrected for the following -

• Speed bias (caused by the mooring motion)
• Sound speed (as electromagnetic current meter sensors use the speed of sound in water to calculate the doppler shift in the returned signal, they are corrected for variations in sound speed using temperature data as sound speed varies with temperature).
• Magnetic variation

A 40 hour low pass filter is also applied to the data.

Calculating and applying calibrations

Manufacturers calibrations are applied.

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 ASCII format as one file per instrument.

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

• The data files are transferred into a common format, a NetCDF subset.

• Standard parameter codes are assigned that accurately describe the data (see Parameter mapping section below).

• Unit conversions are applied, if necessary, so that units are standardised (see Parameter 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.

Parameter mapping

The following describes the parameters contained in the originator's files and their mapping to BODC parameter codes:

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.

Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)

Scientific Rationale

There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). As a consequence of the MOC northwest Europe enjoys a mild climate for its latitude: however abrupt rearrangement of the Atlantic Circulation has been shown in climate models and in palaeoclimate records to be responsible for a cooling of European climate of between 5-10°C. A principal objective of the RAPID programme is the development of a pre-operational prototype system that will continuously observe the strength and structure of the MOC. An initiative has been formed to fulfill this objective and consists of three interlinked projects:

• A mooring array spanning the Atlantic at 26.5°N to measure the southward branch of the MOC (Hirschi et al., 2003 and Baehr et al., 2004).
• Additional moorings deployed in the western boundary along 26.5°N (by Prof. Bill Johns, University of Miami - project MOCHA) to resolve transport in the Deep Western Boundary Current (Bryden et al., 2005). These moorings allow surface-to-bottom density profiles along the western boundary, Mid-Atlantic Ridge, and eastern boundary to be observed. As a result, the transatlantic pressure gradient can be continuously measured.
• Monitoring of the northward branch of the MOC using submarine telephone cables in the Florida Straits (Baringer et al., 2001) led by Dr Molly Baringer (NOAA/AOML/PHOD) - Western Boundary Time Series (WBTS) project.

The UK-led monitoring array system was recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2015 the array continued to be serviced annually under RAPID-WATCH funding. From 2015 until 2021 the array was serviced under RAPID-AMOC funding. Since 2022 the servicing of the array has continued to be funded by the Natural Environment Research Council (NERC). The US-led projects are funded by the National Science Foundation (NSF) (MOCHA project) and NOAA Office of Climate Observations (WBTS project).

The array will be focussed on three regions, the Eastern Boundary (EB), the Mid Atlantic Ridge (MAR) and the Western Boundary (WB). The geographical extent of these regions are as follows:

• Eastern Boundary (EB) array defined as a box with the south-east corner at 23.5°N, 25.5°W and the north-west corner at 29.0°N, 12.0°W
• Mid Atlantic Ridge (MAR) array defined as a box with the south-east corner at 23.0°N, 52.1°W and the north-west corner at 26.5°N, 40.0°W
• Western Boundary (WB) array defined as a box with the south-east corner at 26.0°N, 77.5°W and the north-west corner at 27.5°N, 69.5°W

References

Baehr, J., Hirschi, J., Beismann, J.O. and Marotzke, J. (2004) Monitoring the meridional overturning circulation in the North Atlantic: A model-based array design study. Journal of Marine Research, Volume 62, No 3, pp 283-312.

Baringer, M.O'N. and Larsen, J.C. (2001) Sixteen years of Florida Current transport at 27N Geophysical Research Letters, Volume 28, No 16, pp3179-3182

Bryden, H.L., Johns, W.E. and Saunders, P.M. (2005) Deep Western Boundary Current East of Abaco: Mean structure and transport. Journal of Marine Research, Volume 63, No 1, pp 35-57.

Hirschi, J., Baehr, J., Marotzke J., Stark J., Cunningham S.A. and Beismann J.O. (2003) A monitoring design for the Atlantic meridional overturning circulation. Geophysical Research Letters, Volume 30, No 7, article number 1413 (DOI 10.1029/2002GL016776)

RAPID- Will the Atlantic Thermohaline Circulation Halt? (RAPID-WATCH)

RAPID-WATCH (2007-2014) is a continuation programme of the Natural Environment Research Council's (NERC) Rapid Climate Change (RAPID) programme. It aims to deliver a robust and scientifically credible assessment of the risk to the climate of UK and Europe arising from a rapid change in the Atlantic Meridional Overturning Circulation (MOC). The programme will also assess the need for a long-term observing system that could detect major MOC changes, narrow uncertainty in projections of future change, and possibly be the start of an 'early warning' prediction system.

The effort to design a system to continuously monitor the strength and structure of the North Atlantic MOC is being matched by comparative funding from the US National Science Foundation (NSF) for the existing collaborations started during RAPID for the observational arrays.

Scientific Objectives

• To deliver a decade-long time series (2004-2014) of calibrated and quality-controlled measurements of the Atlantic MOC from the RAPID-WATCH arrays.
• To exploit the data from the RAPID-WATCH arrays and elsewhere to determine and interpret recent changes in the Atlantic MOC, assess the risk of rapid climate change, and investigate the potential for predictions of the MOC and its impacts on climate.

This work will be carried out in collaboration with the Hadley Centre in the UK and through international partnerships.

Mooring Arrays

The RAPID-WATCH arrays are the existing 26°N MOC observing system array (RAPIDMOC) and the WAVE array that monitors the Deep Western Boundary Current. The data from these arrays will work towards meeting the first scientific objective.

The RAPIDMOC array consists of moorings focused in three geographical regions (sub-arrays) along 26.5° N: Eastern Boundary, Mid-Atlantic Ridge and Western Boundary. The Western Boundary sub-array has moorings managed by both the UK and US scientists. The other sub-arrays are solely led by the UK scientists. The lead PI is Dr Stuart Cunningham of the National Oceanography Centre, Southampton, UK.

The WAVE array consists of one line of moorings off Halifax, Nova Scotia. The line will be serviced in partnership with the Bedford Institute of Oceanography (BIO), Halifax, Canada. The lead PI is Dr Chris Hughes of the Proudman Oceanographic Laboratory, Liverpool, UK.

All arrays will be serviced (recovered and redeployed) either on an annual or biennial basis using Research Vessels from the UK, US and Canada.

Modelling Projects

The second scientific objective will be addressed through numerical modelling studies designed to answer four questions:

• How can we exploit data from the RAPID-WATCH arrays to obtain estimates of the MOC and related variables?
• What do the observations from the RAPID-WATCH arrays and other sources tell us about the nature and causes of recent changes in the Atlantic Ocean?
• What are the implications of RAPID-WATCH array data and other recent observations for estimates of the risk due to rapid change in the MOC?
• Could we use RAPID-WATCH and other observations to help predict future changes in the MOC and climate?

Data Activity or Cruise Information

Data Activity

RAPID Moored Instrument Rig WBH2#4

This rig was deployed as part of the Western Boundary (WB) array of the MOCHA/RAPIDMOC project.

The rig was anchored by railway wheels and kept erect by a float at the top of the mooring and groups of small floats distributed along 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

Fixed Station Information

RAPIDMOC/MOCHA Western Boundary (WB) Array

The Western Boundary Array defines a box in which moorings were deployed at the western side of the North Atlantic as part of the RAPIDMOC project and the collaborative project Meridional Overturning Circulation and Heatflux Array (MOCHA). The box region has latitudinal limits of 26° N to 27.5° N and longitudinal limits of 69.5° W to 77.5° W. Moorings have occupied this region since 2004 and are typically deployed for 6 to 18 months.

Moored data summary

Cruise data summary

During the cruises to service the moored array, a variety of data types are collected. The table below is a summary of these data. The number of CTD profiles performed on these cruises within the box region defined above is also included. Trans-Atlantic hydrographic CTD sections have also been performed since 2004 and are included in the table.

Data type ID and description

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: WBH2#4

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: Western Boundary Array

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.