Metadata Report for BODC Series Reference Number 1921522

• 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

Fluorescence CPHLUMTF

The Fluorescence signal increases linearly for most of the cruise until cleaning on 27/03/2017. According to the JC145_NMF_ship_systems_cruise_report, this is due organic build up in the sensor as the signal improved after cleaning on 28/03/2017. The signal decreases to a more realistic level after cleaning and the data are good for the remainder of the cruise.

As seen with the transmittance data, most of the fluorescence data are unreliable and the channel should not be retained.

Fluorescence FVLTWS01

The Fluorescence signal increases linearly for most of the cruise until cleaning on 27/03/2017. According to the JC145_NMF_ship_systems_cruise_report, this is due organic build up in the sensor as the signal improved after cleaning on 28/03/2017. The signal decreases to a more realistic level after cleaning and the data are good for the remainder of the cruise.

As seen with the transmittance data, most of the fluorescence data are unreliable and the channel should not be retained.

Transmittance ATTNDR01

Due to the lack of sensor cleaning throughout the cruise, the transmissometer data shows arbitrary decline for most of the cruise. This is most likely due to trapped bubbles accumulating around the sensor. Prior to this decline, the data are also noisy. The signal increases again after cleaning on 28/03/2017. From this date onwards until the end of the cruise on 08/04/2017, the data are good.

Considering that less than 30 percent of the data in this channel is good, the transmissometer channel has not been retained.

Transmittance POPTDR01

Due to the lack of sensor cleaning throughout the cruise, the transmissometer data shows arbitrary decline for most of the cruise. This is most likely due to trapped bubbles accumulating around the sensor. Prior to this decline, the data are also noisy. The signal increases again after cleaning on 28/03/2017. From this date onwards until the end of the cruise on 08/04/2017, the data are good.

Considering that less than 30 percent of the data in this channel is good, the transmissometer channel has not been retained.

Transmittance TVLTDR01

Due to the lack of sensor cleaning throughout the cruise, the transmissometer data shows arbitrary decline for most of the cruise. This is most likely due to trapped bubbles accumulating around the sensor. Prior to this decline, the data are also noisy. The signal increases again after cleaning on 28/03/2017. From this date onwards until the end of the cruise on 08/04/2017, the data are good.

Considering that less than 30 percent of the data in this channel is good, the transmissometer channel has not been retained.

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

SeaBird Digital Oceanographic Thermometer SBE38

The SBE38 is an ultra-stable thermistor that can be integrated as a remote temperature sensor with an SBE21 Thermosalinograph or an SBE 45 Micro TSG, or as a secondary temperature sensor with an SBE 16 plus, 16plus-IM, 16plus V2, 16plus-IM V2 or 19plus V2 SEACAT CTD.

Temperature is determined by applying an AC excitation to reference resistances and an ultra-stable aged thermistor. The reference resistor is a hermetically sealed VISHAY. AC excitation and ratiometric comparison using a common processing channel removes measurement errors due to parasitic thermocouples, offset voltages, leakage currents and gain errors.

The SBE38 can operate in polled sampling, where it takes one sample and transmits the data, or in continuous sampling.

Specifications

Further details can be found in the manufacturer's specification sheet.

WET Labs WETStar Fluorometers

WET Labs WETStar fluorometers are miniature flow-through fluorometers, designed to measure relative concentrations of chlorophyll, CDOM, uranine, rhodamineWT dye, or phycoerythrin pigment in a sample of water. The sample is pumped through a quartz tube, and excited by a light source tuned to the fluorescence characteristics of the object substance. A photodiode detector measures the portion of the excitation energy that is emitted as fluorescence.

Specifications

By model:

All models:

Further details can be found in the manufacturer's specification sheet, and in the instrument manual.

WETLabs C-Star transmissometer

This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.

Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.

This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.

Specifications

Further details are available in the manufacturer's specification sheet or user guide.

RRS James Cook JC145 Surface Hydrography Instrumentation

Instrumentation

The sea surface hydrographical suite of sensors was fed by the pumped-seawater, non-toxic supply. The depth of the seawater intake was at 5.5 m.

The following surface hydrology sensors were fitted:

SeaBird MicroTSG Thermosalinograph SBE 45

The SBE45 MicroTSG is an externally powered instrument designed for shipboard measurement of temperature and conductivity of pumped near-surface water samples. The instrument can also compute salinity and sound velocity internally.

The MicroTSG comprises a platinum-electrode glass conductivity cell and a stable, pressure-protected thermistor temperature sensor. It also contains an RS-232 port for appending the output of a remote temperature sensor, allowing for direct measurement of sea surface temperature.

The instrument can operate in Polled, Autonomous and Serial Line Sync sampling modes:

• Polled sampling: the instrument takes one sample on command
• Autonomous sampling: the instrument samples at preprogrammed intervals and does not enter quiescence (sleep) state between samples
• Serial Line Sync: a pulse on the serial line causes the instrument to wake up, sample and re-enter quiescent state automatically

Specifications

Further details can be found in the manufacturer's specification sheet.

RRS James Cook JC145 Surface Hydrography Data Processing Procedures

Originator's Data Processing

The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) data logging system into daily NetCDF files which were converted to MSTAR by the originator and provided to BODC for processing. Data was additionally logged into the RVS Level-C format which have been archived at BODC.

Files delivered to BODC

BODC Data Processing

The files were reformatted to BODC internal format using standard data banking procedures. All files were averaged to 60 second intervals. The following table shows how the variables within the files were mapped to appropriate BODC parameter codes:

met_tsg_jc145_01_medav_clean_cal.nc

All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag.

Calibration

Field Calibrations

No field calibrations have been applied.

Manufacturers Calibrations

Transmissometer

The transmissometer voltage channel was converted to beam transmission ( beamtrans ) and beam attenuation ( atten ) as follows:

beamtrans [%] = ([ volts - Vdark ] / [ Vref - Vdark ])100

atten [per m] = (-1/ pathlength ) ln( beamtrans /100)

where Vdark = 0.058 V, Vref = 4.667 V and pathlength = 0.25 m.

Fluorometer

The fluorescence voltage channel was converted to engineering units ( chla ) using the following calibration:

chla [µg/L]= SF ( volts - CWO )

where SF = 15.8 µg/L/V and CWO = 0.050 V.

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) 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)

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

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

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: