Metadata Report for BODC Series Reference Number 768800
Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
Metadata Summary
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Problem Reports
No Problem Report Found in the Database
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
Instrument Description
CTD unit and auxiliary sensors
The CTD system used on cruise D324 was the Sea-Bird 911 plus, with a Sea-Bird 32 carousel. Several of the Niskin bottles were removed from the frame, to accommodate moored instruments for calibration purposes. During the cruise various problems with sensors required them to be replaced on the CTD frame (see Section 6.2 of the D324 cruise report). The table below shows which sensors were attached to the CTD frame and on which casts.
| Sensor | Serial Number | Casts | Last calibration date |
|---|---|---|---|
| SBE 911+ deck unit | 0636 | 1-2 | September 2007 |
| SBE 911+ deck unit | 0637 | 3-13 | September 2007 |
| SBE 32 carousel | 0518 | 1-13 | January 2005 |
| Primary Temperature SBE-03P | 4151 | 1 | June 2007 |
| Primary Temperature SBE-03P | 2674 | 2-3 | August 2007 |
| Primary Temperature SBE-03P | 4301 | 4-13 | September 2007 |
| Secondary Temperature SBE-03P | 2674 | 1,4-13 | August 2007 |
| Secondary Temperature SBE-03P | 4301 | 2-3 | September 2007 |
| Primary Conductivity SBE-04C | 2231 | 1-3 | August 2007 |
| Primary Conductivity SBE-04C | 2580 | 4-13 | September 2007 |
| Secondary Conductivity SBE-04C | 2450 | 1 | August 2007 |
| Secondary Conductivity SBE-04C | 2580 | 2-3 | September 2007 |
| Secondary Conductivity SBE-04C | 2231 | 4 | August 2007 |
| Secondary Conductivity SBE-04C | 2841 | 5-13 | September 2007 |
| Pressure-Digiquartz | 83008 | 1-2 | May 05 |
| Pressure-Digiquartz | 79501 | 3-13 | September 2006 |
| Benthos PSA-916T Altimeter | 1040 | 1-13 | April 2007 |
| RD Instruments 150kHz BroadBand LADCP | 1503 | 1-7,11-13 | - |
The salinity samples from the CTD were analysed during the cruise using the Guildline Autosal model 8400B(serial number 60889). The Autosal was standardised using batch P147 IAPSO Standard Seawater.
Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers
The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.
Underwater unit
The CTD underwater unit (SBE 9 or SBE 9 plus) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus, that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.
Temperature, conductivity and pressure sensors
The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.
The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.
Additional sensors
Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.
Deck unit or SEARAM
Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus.
Specifications
Specifications for the SBE 9 plus underwater unit are listed below:
| Parameter | Range | Initial accuracy | Resolution at 24 Hz | Response time |
|---|---|---|---|---|
| Temperature | -5 to 35°C | 0.001°C | 0.0002°C | 0.065 sec |
| Conductivity | 0 to 7 S m-1 | 0.0003 S m-1 | 0.00004 S m-1 | 0.065 sec (pumped) |
| Pressure | 0 to full scale (1400, 2000, 4200, 6800 or 10500 m) | 0.015% of full scale | 0.001% of full scale | 0.015 sec |
Further details can be found in the manufacturer's specification sheet.
BODC Processing
The data arrived at BODC in 12 PSTAR format files representing the CTD casts conducted during cruise D324. Cast C001 was not processed by the originator as this was a test cast and therefore not lodged with BODC. The lodged casts were reformatted to BODC's internal netcdf format using transfer function 360. The following table shows the mapping of variables within the PSTAR files to appropriate BODC parameter codes:
| Originator' Variable | Units | Description | BODC Parameter Code | Units | Comments |
|---|---|---|---|---|---|
| press | dbar | Pressure exerted by the water column | PRESPR01 | dbar | Manufacturer's calibration applied. |
| temp | °C | Temperature of the water column by CTD (Primary sensor) | TEMPCU01 | °C | ITS-90 |
| temp2 | °C | Temperature of the water column by CTD (Secondary sensor) | TEMPCU02 | °C | ITS-90 |
| salin | - | Practical salinity of the water column (Primary sensor data) | PSALCC01 | - | Calibrated by data originator with discrete salinity samples. |
| salin2 | - | Practical salinity of the water column (Secondary sensor data) | PSALCC02 | - | Calibrated by data originator with discrete salinity samples. |
| potemp | °C | Potential temperature of the water column (Primary sensor) | POTMCV01 | °C | Not transferred |
| potemp2 | °C | Potential temperature of the water column (Secondary sensor) | POTMCV02 | °C | Not transferred |
| cond | mS/cm | Electrical conductivity of the water column (Primary sensor) | CNDCST01 | S/m | /10 |
| cond2 | mS/cm | Electrical conductivity of the water column (Secondary sensor) | CNDCST02 | S/m | /10 |
| lat | ° | Latitude North | ALATGP01 | ° | Not transferred |
| lon | ° | Longitude East | ALONGP01 | ° | Not transferred |
| sigma0 | kg/m-3 | Potential density of the water column relative to 0 dbar | - | - | Not transferred |
| sigma2 | kg/m-3 | Potential density of the water column relative to 2000 dbar | - | - | Not transferred |
| alt | m | Altimeter height | - | - | Not transferred |
| time | seconds | Time in seconds since 01/01/2007 00:00:00 | - | - | Not transferred |
| jday | jday | Julian days | - | - | Not transferred |
| flag | - | Bad data flag | - | - | All 0.0 which is originators good data flag |
| - | - | - | SIGTPR01 | kg/m-3 | Potential density calculated by BODC using PRESPR01, TEMPCU01, PSALCC01 |
| - | - | - | SIGTPR02 | kg/m-3 | Potential density calculated by BODC using PRESPR01, TEMPCU02, PSALCC02 |
The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, and missing data marked by both setting the data to an appropriate value and setting the quality control flag.
Originator's Data Processing
Sampling Strategy
A total of 13 CTD casts were performed during the cruise along the Eastern boundary and Mid Atlantic Ridge sections of the 26.5N RAPIDMOC array. The CTD casts provided start-point calibrations for instruments to be deployed and end-point calibrations for recovered instruments. For recovered instruments that were re-deployed, the post-deployment cast provided a pre-deployment calibration. The instruments were set to the fastest sampling rate and the CTD lowered as normal. On the upcast, the bottle stops were increased to 5 minutes to allow time for stabilisation and the provision of more accurate data. To allow the instruments to be attached to the CTD frame using bespoke attachments, upto 12 sample bottles were removed on all casts.
Data Processing
Raw CTD data were transferred from the SeaBird deck unit to a PC via SeaBird software (Seasave Win32 version 5.35). Physical units were calculated from the frequency data using the manufacturer's calibration routines and the data converted to ASCII format. The ASCII files were converted to PSTAR format and in-house programs were run to reduce the frequency of the data from 24Hz to 1Hz, and for the downcast to be averaged to a 2db pressure grid. A calibration was produced for the CTD conductivity sensor by merging the salinity sample data with the CTD data
Field Calibrations
Independent salinity samples, obtained from the CTD rosette, were used to calibrate the CTD salinity data. Bottle samples with incorrect conductivities were identified and removed from the calibration. Data were initially rejected where conductivity differences were greater than +/-0.02 mS/cm and where the ratio K= {Cbot/CCTD} exceeded the limits 0.9999 - 1.0006 (where {} denotes station average) and also +/- 3 standard deviations of the new station mean.
A slope correction to account for sensor drift was applied such that CCTDcorrected1=CCTD*K where K=1.000107.
A second order polynomial fit was then fitted to CBOT/CCTD as a function of CCTD, giving K1= 1.000536- 2.1578e-05xCbot + 1.8946e-07x Cbot 2 and CCTDcorrected=CCTDcorrected1*K1.
References
Cunningham, S.A Kanzow, T. and et al,. Rayner, D. (ed.) (2008) Cruise Report No. 34 RRS Discovery Cruise D324, 06 Oct-09 Nov 2007. RAPID Mooring cruise report
General Data Screening carried out by BODC
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:
- Times for instrument deployment and for start/end of data series
- Length of record and the number of data cycles/cycle interval
- Parameters expected 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 or depth 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 data values will not be altered.
The following types of irregularity, each relying on visual detection in the 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 then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.
Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:
- Maximum and minimum values of parameters (spikes excluded).
- The occurrence of meteorological events.
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.
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) 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).
The entire monitoring array system created by the three projects will be recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2014 the array will continue to be serviced annually under RAPID-WATCH funding.
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)
Data Activity or Cruise Information
Cruise
| Cruise Name | D324 |
| Departure Date | 2007-10-06 |
| Arrival Date | 2007-11-09 |
| Principal Scientist(s) | Stuart A Cunningham (National Oceanography Centre, Southampton) |
| Ship | RRS Discovery |
Complete Cruise Metadata Report is available here
Fixed Station Information
Fixed Station Information
| Station Name | Mid-Atlantic Ridge Array |
| Category | Offshore area |
| Latitude | 24° 45.00' N |
| Longitude | 45° 30.00' W |
| Water depth below MSL |
RAPIDMOC Mid-Atlantic Ridge (MAR) Array
The Mid-Atlantic Ridge Array defines a box in which moorings are 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 have occupied this region since 2004 and are 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
| Year | Cruise ID | Number of moorings | Data types (number of instruments) |
|---|---|---|---|
| 2004 | D277 | 4 | BPR (4), CM (5), MCTD (20), MMP (1) |
| 2005 | CD170 | 6 | BPR (4), CM (6), MCTD (24) |
| 2006 | D304 | 5 | BPR (3), CM (3), MCTD (32) |
| 2007 | D324 | 6 | BPR (4), CM (3), MCTD (33) |
| 2008 | D334 | 6 | BPR (4), CM (3), MCTD (39) |
| 2009 | D344 | 6 | BPR (6), CM (3), MCTD (40) |
| 2010 | D359 | 6 | BPR (6), CM (5), MCTD (40) |
| 2011 | JC064 | 6 | BPR (6), CM (5), MCTD (40) |
| 2012 | D382 | 6 | BPR (6), CM (5), MCTD (34) |
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.
| Cruise ID | Cruise description | Data types | Number of CTD profiles performed within the box region |
|---|---|---|---|
| D277 | Initial array deployment | DIS, MET, NAV, SADCP, SURF | - |
| D279 | Hydrographic section | CTD, DIS, LADCP, MET, NAV, SADCP, SURF | 19 |
| CD170 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 5 |
| D304 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 1 |
| D324 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 3 |
| D334 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 5 |
| D344 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 5 |
| D346 | Hydrographic section | CTD, DIS, LADCP, MET, NAV, SADCP, SURF | 21 |
| D359 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 5 |
| JC064 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 6 |
| D382 | Array service | CTD, DIS, MET, NAV, SADCP, SURF | 3 |
Data type ID and description
| Data type ID | Description |
|---|---|
| ADCP | Acoustic Doppler Current Profiler |
| BATH | Bathymetry |
| BPR | Bottom Pressure Recorder |
| CM | Current Meter |
| CTD | Conductivity-Temperature-Depth profiler |
| DIS | Discrete water bottle samples |
| IES | Inverted Echo Sounder |
| LADCP | Lowered Acoustic Doppler Current Profiler |
| MET | Meteorology |
| MCTD | Moored Conductivity-Temperature-Depth sensor |
| MMP | McLane Moored Profiler - profiling CTD and current meter |
| NAV | Navigation |
| SADCP | Shipborne Acoustic Doppler Current Profiler |
| SURF | Sea surface data |
Other Series linked to this Fixed Station for this cruise - 768793 768812 863777 863789 863790 863808 863821 863833 863845 863857 863869 863870 863882 863894 863901 863913 863925 863937 863949 863950 863962 863974 863986 863998 864001 864013 864025 864037 864049 864050 864062 864074 864086 864098 864105 945968 946007 946019 946044
Other Cruises linked to this Fixed Station (with the number of series) - CD170 (33) D277 (24) D304 (31) D324 (39) D334 (29) D344 (37) D346 (21) D359 (45) JC064 (41)
BODC Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
| Flag | Description |
|---|---|
| Blank | Unqualified |
| < | Below detection limit |
| > | In excess of quoted value |
| A | Taxonomic flag for affinis (aff.) |
| B | Beginning of CTD Down/Up Cast |
| C | Taxonomic flag for confer (cf.) |
| D | Thermometric depth |
| E | End of CTD Down/Up Cast |
| G | Non-taxonomic biological characteristic uncertainty |
| H | Extrapolated value |
| I | Taxonomic flag for single species (sp.) |
| K | Improbable value - unknown quality control source |
| L | Improbable value - originator's quality control |
| M | Improbable value - BODC quality control |
| N | Null value |
| O | Improbable value - user quality control |
| P | Trace/calm |
| Q | Indeterminate |
| R | Replacement value |
| S | Estimated value |
| T | Interpolated value |
| U | Uncalibrated |
| W | Control value |
| X | Excessive difference |
