Metadata Report for BODC Series Reference Number 1161109

• 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

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 WAVE Sea-Bird MicroCAT data processing document

This document outlines the procedures undertaken to process and quality assure the MicroCAT data collected under the RAPID WAVE project.

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

The pressure (when applicable) and temperature-conductivity data were calibrated according to the following prescription: For each instrument, two calibration casts were performed. One previous to instrument deployment and one after recovery. Regression coefficients derived from these casts were used to calibrate the pressure, temperature and conductivity from the MicroCATs. A calibration cast consists in clamping one or more MicroCATs to the CTD rosette and carrying out simultaneous measurements with both the MicroCATs and the on-board calibrated CTD instrument package. Measurements taken during the upward part of the cast by stationing the rosette at a particular depth for an interval of between 10 and 15 minutes are used to obtain linear calibration coefficients for temperature, conductivity and, if applicable, pressure. Because the reference CTD takes samples at 24 Hz, while the MicroCATs sample at between 15 and 30 second intervals, the MicroCAT measurements are interpolated linearly in time to obtain as many samples as the reference CTD. As the reference CTD does not have measurements of the time of day, the synchronisation between the measurements of the CTD and the MicroCAT instruments is approximate. However, this calibration procedure is possible because the plateaus of pressure are easily detectable by eye. The calibration coefficients derived from the pre-deployment and post-recovery casts can then be combined to provide calibration coefficients that vary linearly in time over the period when the instrument was moored.

Calibration procedure and salinity computation

The 10-15 minute plateaus were determined and for each plateau correlation coefficient R and regression coefficients A and B were computed:

CTD = A * MC + B

This procedure was applied to each of the three properties: T, C and P (where available). Although care was taken to ensure that no data points outside the plateaus were employed in the analysis, some scatter plots revealed obvious outliers. They were removed as follows:

In the cases where R was less than 0.75, the data point, which was the farthest from the linear trend, was rejected. The correlation coefficient and the coefficients of the linear approximation were then re-computed. The iterative process continued until the correlation coefficient became at least 0.75. Next, the despiked plateaus were concatenated and new values of A and B were determined from the data merged in such manner. These values of A and B were then applied to the entire record from the corresponding instrument as:

MC_calibrated = A * MC_raw + B

Next, outliers were eyeballed and removed. These happened to be only in conductivity records: the temperature and pressure data were clean. The calibrated records of T, C and P (where P was measured) were then used for the computation of salinity, using the UNESCO 1983 algorithm of Fofonoff and Millard (1983) as implemented by the CSIRO seawater Matlab package version 3.2. Despite the fact that the conductivity had been despiked and the series of T and P were spikeless, there were some salinity spikes after the computation. They were identified by eye and removed.

BODC were not supplied with the calibration coefficient values, however, these can be calculated using the raw and corresponding calibrated data values. Raw data can be obtained from BODC if this is required by the user.

BODC processing

The data files were submitted in ASCII 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.

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

• The data are screened visually and any spikes or instrument malfunctions can be clearly labelled with quality control flags.

• Data files are trimmed to remove the pre deployment and post recovery data cycles that are null.

• 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 Western Atlantic Variability Experiment (WAVE)

Introduction

The RAPID WAVE project began in 2004 as an observational component of the U.K Natural Environment Research Council's RAPID Climate Change Programme in the western North Atlantic Ocean. In 2008, funding to continue RAPID WAVE was secured through the continuation programme, RAPID-WATCH, which is due to end in 2014.

The RAPID WAVE team brings together scientists at the National Oceanography Centre in Liverpool. Between 2004 and 2010, the RAPID WAVE team also contributed to the Line W mooring array, joining colleagues from the U.S. Line W is a U.S-led initiative used to monitor the North Atlantic Ocean's deep western boundary current whilst being funded through the U.S National Science Foundation and has been active since October 2001. It brings together scientists from Woods Hole Oceanographic Institution (WHOI) and Lamont-Doherty Earth Observatory (LDEO). Users of these data are referred to the Line W Project Website for more information.

In 2007, further collaboration was established with scientists at the Bedford Institute of Oceanography (BIO). This arrangement was formalised and continues under RAPID-WATCH. Smaller scale collaboration with scientists at the Instituto Espanol de Oceanografia (IEO) during RAPID-WATCH saw additional RAPID WAVE observational work in the eastern North Atlantic Ocean. This work commenced in 2009 as part of the RAPID WAVE RAPIDO campaign.

Scientific Rationale

The primary aim of the RAPID WAVE project is to develop an observing system that will identify the propagation of overturning signals, from high to low latitudes, along the western margin of the North Atlantic. It specifically aims to monitor temporal changes in the Deep Western Boundary Current and reveal how coherent the changes are along the slope. Ultimately it is envisaged that this will enable scientists to develop a better understanding of larger-scale overturning circulation in the Atlantic, and its wider impacts on climate.

Fieldwork

The fieldwork aspect of the project was to deploy arrays of Bottom Pressure Recorders (BPRs) and CTD moorings along specified satellite altimeter groundtracks off the eastern continental slope of Canada and the United States. In 2004, fieldwork focused on three array lines. Line A was established heading south west from the Grand Banks, whilst the Line B array ran south east on the continental slope of Nova Scotia. The third line, Line W, was an established hydrographic array on the continental slope of New England, serviced by Woods Hole Oceanographic Institute (WHOI), to which RAPID WAVE contributed BPR instrumentation.

The original intention was that each array would be serviced by a cruise every two years. However, following a very poor return rate of instrumentation during the first servicing cruise of Lines A and B in 2006, this plan was modified significantly, and the decision made to abandon work on Line A. In 2007, additional logistical support from Canada's Bedford Institute of Oceanography (BIO) enabled Line B to be serviced again after just one year of deployment, with a much improved recovery record.

The transition from RAPID to RAPID-WATCH funding marked significant changes to the RAPID WAVE observational system. Line B was abandoned and a joint array with BIO, known as the RAPID Scotia Line, to the south west was developed. This line receives annual servicing by BIO, with cruise participation from the RAPID WAVE team.

The servicing of RAPID WAVE BPRs on Line W remained a biennial activity during the RAPID and RAPID-WATCH programmes.

A small number of BPR deployments have also taken place off the coast of Spain as part of the RAPIDO element of RAPID WAVE.

Instrumentation

Types of instruments and measurements:

• Moored BPRs
• Moored CTD/CT loggers
• Moored current meters (RAPID-WATCH)
• Moored ADCPs (RAPID-WATCH)
• Shipboard measurements: CTD, underway, salinity, LADCP, ADCP

Contacts

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 RS6LM#2

This rig was deployed as part of the Halifax/Line RS array of the RAPID WAVE project.

The rig was anchored by a cast iron sinker and kept erect by groups of buoyancy spheres attached along the mooring.

Instruments deployed on the rig

All nominal depths have been sourced from the deployment cruise report.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

RAPID Mooring Site RS6

This fixed station forms part of the RAPID Scotia mooring array located on the Scotian Shelf, Nova Scotia. The RAPID Scotia array is deployed as part of the RAPID WAVE project under the RAPID-WATCH programme. This array acts as an extension to the existing Halifax Line, maintained by Bedford Institute of Oceanography (BIO), Canada.

Site occupations

* Only the top part of mooring was salvaged after dragging.

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: RS6LM#2

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: RAPID WAVE Site RS6

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.