Metadata Report for BODC Series Reference Number 1846796

• 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

Sea-Bird SBE 37-SMP MicroCAT

The SBE 37-SMP MicroCAT is a high accuracy conductivity and temperature recorder (pressure optional) with Serial interface, internal battery, non-volatile FLASH Memory and integral Pump. The Integral Pump runs for 1 second each time the MicroCAT samples, improving the conductivity response and giving improved anti-foul protection.

Designed for moorings and other long-duration, fixed-site deployments, MicroCATs have non-corroding titanium housings rated for operation to 7000 meters or pressure sensor full scale-range. Communication with the MicroCAT is over an internal, 3-wire, RS-232C link. The MicroCAT's aged and pressure-protected thermistor has a long history of exceptional accuracy and stability (typical drift is less than 0.002°C per year). Electrical isolation of the conductivity electronics eliminates any possibility of ground-loop noise.

Specifications

Further information can be found via the following link: Sea-Bird SBE 37-SMP MicroCAT Datasheet

RAPID-AMOC Calibration Coefficients

Due to the loss of the upper part of the mooring on 07/10/2016, data were split into two records before (A) and after (B) the event for calibration purposes.

Processing log A

Average conductivity applied? y
Average temperature applied? y
Average pressure applied? y
Pressure drift removal? y
Equation of pressure drift fit: yfit = a1*(1-exp(-a2*(x-x(1)))) + a3*(x-x(1)) + a4
Coefficients of pressure drift fit: a1 = 0.712121, a2 = 0.035799, a3 = -0.000054, a4 = 4579.416226
Conductivity pressure correction redone? n
Skipped conductivity intervals: [0]
Skipped temperature intervals : [0]
Skipped pressure intervals : [0]
Number of additional C points skipped interactively: [0]
Number of additional C points skipped automatically: [0]

Processing log B

Average conductivity applied? y
Average temperature applied? y
Average pressure applied? y
Pressure drift removal? n
Conductivity pressure correction redone? n
Skipped conductivity intervals: [0]
Skipped temperature intervals : [0]
Skipped pressure intervals : [0]
Number of additional C points skipped interactively: [0]
Number of additional C points skipped automatically: [3]

RAPIDMOC/MOCHA Sea-Bird MicroCAT data processing document

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

Originator's processing

The raw data are downloaded from the instrument and converted to ASCII format. All processing is performed in Matlab.

Calculating calibration coefficients

Prior to deployment and on recovery, a CTD dip is performed with the MicroCATs strapped onto the CTD frame. This allows calibration of the MicroCAT data by comparing the MicroCAT data with the CTD data. As the MicroCATs adjustment is much slower than the CTD, data are only compared during bottle stops and after the sensors have adjusted. Bottle stops on these calibration dips last no less than 5 minutes.

Any discrepancy between the MicroCAT clock and the CTD clock is calculated and corrected if necessary.

An average offset (MicroCAT - CTD) is calculated for temperature, conductivity and pressure during the stable period of each bottle stop and interpolated onto the instrument deployment depths. For temperature and conductivity, an average of the offsets derived during the bottle stops is calculated for a specified pressure range where the data are stable (deep water). For pressure, the average offset interpolated to the deployment depth is used. If the calibration dip is shallower than the deployment depth, the offset is extrapolated to the deployment depth.

All the offsets are visually checked and adjusted if necessary. For temperature, if the calculated offsets are less than 0.003 in magnitude no offset is applied i.e. the offsets are adjusted to 0.000.

Applying calibrations

The data are calibrated using the pre and post deployment calibration coefficients. The calibration can be applied as either

• A linear trend between the pre and post deployment coefficients
• A constant offset using the pre deployment coefficient
• A constant offset using the post deployment coefficient
• A constant offset using an average of the pre and post deployment coefficients
• A general linear trend using either the pre or post deployment coefficient

If required, a conductivity pressure correction can be applied. This is used if the pressure channel shows spurious data in a particular time interval. A drift in the pressure data can also be removed.

To aid the quality of the calibration, data from CTD casts performed near mooring locations on previous cruises are used as a reference and are visually compared with the MicroCAT data.

Quality control

All variables in specified time intervals can be set to dummy values if the data are suspect and it is also possible to apply an offset to a subsection of a particular channel, if required. Interactive despiking can be carried out on the temperature and conductivity data, if present, by selecting data based on a T-S plot. Automatic despiking can also be performed using the option to exclude data outside the 6σ area.

The last stage of the processing is to grid the data onto a pressure field and visually check against historical data. This enables the calibrations to be checked and adjusted if necessary. On occasion, comparison of the time series with historical data and series from nearby instruments highlights the need for removal of a drift from one or more data channels. This is accomplished by removing a linear trend from the appropriate channel(s) and may affect the entire series or a subsection thereof. If a trend has been removed it will be noted in the 'RAPIDMOC Calibration Coefficients' section of the documentation.

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).

• Salinity is derived using UNESCO 1983 polynomial.

• 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:

Parameter derivation

The following describes the parameters derived by BODC and their mapping to BODC parameter codes:

Project Information

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 Climate Change - Atlantic Meridional Overturning Circulation (RAPID-AMOC)

RAPID-AMOC is an £8.4 million, 7 year (2013-2020) research programme that builds on the success of the Natural Environment Research Council's (NERC) RAPID and RAPID-WATCH programmes and will deliver a 16 year long time series of the Atlantic Meridional Overturning Circulation (AMOC).

Background

The Atlantic Meridional Overturning Circulation (AMOC) is a critical element in the energy balance of the global climate system. The AMOC consists of a near-surface, warm northward flow of ocean water, compensated by a colder southward return flow at depth. This heat is transferred from the ocean to the atmosphere at mid-latitudes, with a substantial impact on climate and, in particular, on that of the UK and northwest Europe.

Observing and understanding changes in the AMOC is critically important for identifying the mechanisms of decadal climate variability and change, and for interannual-to-decadal climate prediction. This includes predicting changes in the location, frequency and intensity of Atlantic hurricanes, storms in the North Atlantic and over Europe, shifts in tropical and European precipitation patterns, and the response of sea level to changing radiative forcing. Sustained observations are also critical for assessing the possibility of abrupt change in the AMOC that are known to occur in palaeoclimatic records.

Since 2004 the NERC RAPID and RAPID-WATCH programmes, in partnership with the National Science Foundation and the National Oceanic and Atmospheric Administration in the US, have supported an observing system to continuously measure the AMOC at 26.5°N via a trans-basin array of moored instruments. This measures the basin-wide strength and vertical structure of the AMOC, and its components.

Observations from the array have already revolutionised understanding of AMOC variability and documented its variability on seasonal to interannual timescales. The first few years of observations, demonstrated the feasibility of AMOC measurement, provided new insights into the seasonal cycle, and allowed apparent trends in previous historical 'snapshots' to be seen in the context of natural variability. RAPID-AMOC will extend the AMOC time series.

Objective

RAPID-AMOC's overall objective is to determine the variability of the AMOC, and its links to climate and to the ocean carbon sink, on interannual-to-decadal time scales

This will be achieved by the continued support of the monitoring array and supporting the use of the data in three key areas:

• Application of array data for improved ocean state estimation;
• Use of array data to understand the role of the AMOC in climate variability and predictability;
• Addition of biogeochemical sensors to the array and use to constrain biogeochemical fluxes.

Three projects have been funded to address the objectives of RAPID-AMOC:

• Reanalysis of the AMOC
• DYNamics and predictability of the Atlantic Meridional Overturning and Climate (DYNAMOC)
• Atlantic BiogeoChemical fluxes (ABC Fluxes)

Data Activity or Cruise Information

Data Activity

RAPID Moored Instrument Rig MAR1#11

This rig was deployed as part of the Mid Atlantic Ridge (MAR) array of the RAPIDMOC project.

The rig was anchored by a 2100 kg anchor and kept erect by a 37" steel float at approximately 109 m depth supplemented by groups of smaller floats distributed along the mooring.

Instruments deployed on the rig

Data quality

The upper section of MAR1 was lost during its 18 month deployment. The mooring collapsed on October 7, 2016 when the wire parted above the 162m MicroCAT. All instruments above this section were lost.

*Instruments SMP MicroCATs #3269, #6802, #5789, and IMP MicroCAT #4719 sensors dropped due to the mooring collapse on October 7, 2016.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

RAPIDMOC Mid-Atlantic Ridge (MAR) Array

The Mid-Atlantic Ridge Array defines a box in which moorings were deployed either side of the Mid-Atlantic Ridge in the North Atlantic as part of the RAPIDMOC project. The box region has latitudinal limits of 23° N to 26.5° N and longitudinal limits of 40° W to 52.1° W. Moorings occupied this region between 2004 and 2020, and were typically deployed for 12 to 18 months.

Moored data summary

A description of the data types can be found at the bottom of this document

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: MAR1#11

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: Mid-Atlantic Ridge 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.