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Metadata Report for BODC Series Reference Number 1643330

Metadata Summary

Data Description

Data Category Water column chemistry
Instrument Type
Ruthern Instruments marine pH monitor  pH sensors
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Cynthia Dumousseaud
Originating Organization University of Southampton School of Ocean and Earth Science
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Oceans 2025
Oceans 2025 Theme 10
Oceans 2025 Theme 10 SO4

Data Identifiers

Originator's Identifier PH_UNDERWAY_CD6
BODC Series Reference 1643330

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2007-07-26 13:31
End Time (yyyy-mm-dd hh:mm) 2007-08-22 20:37
Nominal Cycle Interval 60.0 seconds

Spatial Co-ordinates

Start Latitude 57.08600 N ( 57° 5.2' N )
End Latitude 63.09600 N ( 63° 5.8' N )
Start Longitude 22.53400 W ( 22° 32.0' W )
End Longitude 11.26900 W ( 11° 16.1' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth 5.0 m
Maximum Sensor or Sampling Depth 5.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
Sea Floor Depth Source -
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor or Sampling Depth Datum Approximate - Depth is only approximate
Sea Floor Depth Datum -


BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ACYCAA011DimensionlessSequence number
ALATGP011DegreesLatitude north relative to WGS84 by unspecified GPS system
ALONGP011DegreesLongitude east relative to WGS84 by unspecified GPS system
PHXXPR011pH unitspH per unit volume of the water body by pH electrode

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

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

Ruthern Instruments Marine pH Monitor

A pH monitor designed for use in estuarine and coastal waters. The sensor is based on a capillary liquid junction and pH is measuremed on the free ion concentration scale. The instrument measures pH of a pumped water supply, either continuously or in batch mode.

This system was built in collaboration with the UK Environment Agency and the Plymouth Marine Laboratory. Two versions were developed: one for permanent bulkhead mounting in small coastal vessels and a portable version for up-stream use in small boats.


Accuracy better than ± 0.01 pH units
Salinity range 1 to 40 ppt
Temperature precision 0.02°C

Further details can be found here.

BODC data processing

The data were supplied to BODC in .xls format. These were reformatted to the internal BODC NetCDF format. The following table shows how the variables in the .xls file were mapped to appropriate BODC parameter codes

Originator's Variable Originator's Units Description BODC Parameter Code Units Comments
pH(H1) pH pH per unit volume of the water body by pH electrode PHXXPR01 pH -
pH(H2) pH pH per unit volume of the water body by pH electrode - - Secondary Channel, not retained

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 setting both the data to an appropriate value and setting the quality control flag.

Detailed metadata and documentation were compiled and linked to the data.

Originator's Data Processing

Sampling strategy

During cruise D321A a potentiometric pH system was installed on the non-toxic sea water supply and was run continuously during the cruise. The measurements were set to a rate of 1 minute intervals.The potentiometric method for the determination of pH in seawater consists of the measurement of the electromotive force (emf) of a cell composed of a silver/silver chloride electrode and a glass pH electrode. The instrument used for the determination of pH was the portable pH monitor from Ruthern Instrument.

Data calibration and initial processing

To avoid errors with electrode drift, calibration of the system was undertaken every 8 to 12 hours with Tris buffer made up in artificial sea water according to Millero et al. (1986). The buffer was kept in a fridge between each calibration and was brought approximately to the sea water temperature (within 5°C) in order to maximize the accuracy. The temperature of the pH cell was recorded using a Platinum Resistance Thermometer (0.1°C precision). The accuracy of the method was established from the comparison between pH obtained from calibration and calculated pH and estimated as 0.02 pH units. The overall precision of the method is of 0.01 pH unit. The pH scale used in the pH calculation of the system is the free hydrogen ion concentration scale : pHF, which uses the concentration of free proton to define the hydrogen ion activity (Bates, 1975). The preliminary results of the potentiometric pH were compared with the Fluorescence data and the pCO2 data, by the originator, suggesting high resolution data. For more information see the Cruise Report

The data were supplied to BODC for banking.


Bates R.G. (1975). pH scales for seawater. In: The nature of seawater. Phys. Chem. Sci. Res., 315-338.

Millero F.J., A.G. Dickson, G. Eischeid, C. Goyet, P. Guenther, K.M. Johnson, R.M. Key, K. Lee, D. Purkenson, C.L. Sabine, R.G. Schottle, D.W.R. Wallace, E. Lewis, C.D. Winn (1998). Assessment of the quality of the shipboard measurements of total alkalinity on the WOCE Hydrographic Program Indian Ocean CO2 survey cruises 1994-1996. Marine Chemistry, 63, 9-20.

D326 Underway pH Instrumentation

The pH monitor from Ruthern Instruments employs a potentiometric method for the determination of pH in seawater. The system consists of a highly reproducible free-diffusion liquid junction. A capillary liquid junction is formed between the reference reservoir (containing the silver/silver chloride electrode) and the pH cell (containing the pH electrode and the sample to be analysed). The bridge solution (2.5 M KCl in deonised water) allows the ionic contact between the hydrogen and reference electrode and is introduced below the sample via a solenoid pump.

Project Information

Oceans 2025 Theme 10

Oceans 2025 is a strategic marine science programme, bringing marine researchers together to increase people's knowledge of the marine environment so that they are better able to protect it for future generations.

Theme 10: Integration of Sustained Observations in the Marine Environment spans all marine domains from the sea-shore to the global ocean, providing data and knowledge on a wide range of ecosystem properties and processes (from ocean circulation to biodiversity) that are critical to understanding Earth system behaviour and identifying change. They have been developed not merely to provide long-term data sets, but to capture extreme or episodic events, and play a key role in the initialisation and validation of models. Many of these SOs will be integrated into the newly developing UK Marine Monitoring Strategy - evolving from the Defra reports Safeguarding our Seas (2002) and Charting Progress (2005), thus contributing to the underpinning knowledge for national marine stewardship. They will also contribute to the UK GOOS Strategic Plan (IACMST, 2006) and the Global Marine Assessment.


Oceans 2025 Theme 10, Sustained Observation Activity 4: The Extended Ellett Line

The Ellett Line (begun in 1975 and since 1996 the Extended Ellett Line from Scotland to Iceland) crosses important north Atlantic Meridional Overturning Circulation (MOC) components and thus provides an additional contribution to understanding the north Atlantic response to climate change. Sustained Observation Activity (SO) 4 will repeat this section annually collecting a wide variety of physical and biogeochemical measurements, and will, to enhance the time variable component, make use of Argo floats and gliders. SO 4 will be implemented by physical, biological and chemical scientists at the National Oceanography Centre, Southampton (NOCS) and the Scottish Association for Marine Science (SAMS).

SO 4 formally contributes to the Department for Environment, Food and Rural Affairs (DEFRA)-funded Marine Environmental Change Network (MECN). Established in 2002 to coordinate and promote the collection and utilisation of marine time-series and long-term data sets, the goal of the network is to use long-term marine environmental data from around the British Isles and Ireland to separate natural fluctuations from global, regional and local anthropogenic impacts.

The specific deliverables for SO 4 are:

  • A time series of the evolution of the hydrography of the northeast Atlantic, together with a more formal understanding of the causes of any changes observed
  • An archived data set available to the international community via the British Oceanographic Data Centre (BODC)
  • A platform for further scientific research

More detailed information on this Work Package is available at pages 15 - 16 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10


Oceans 2025 - The NERC Marine Centres' Strategic Research Programme 2007-2012

Who funds the programme?

The Natural Environment Research Council (NERC) funds the Oceans 2025 programme, which was originally planned in the context of NERC's 2002-2007 strategy and later realigned to NERC's subsequent strategy (Next Generation Science for Planet Earth; NERC 2007).

Who is involved in the programme?

The Oceans 2025 programme was designed by and is to be implemented through seven leading UK marine centres. The marine centres work together in coordination and are also supported by cooperation and input from government bodies, universities and other partners. The seven marine centres are:

  • National Oceanography Centre, Southampton (NOCS)
  • Plymouth Marine Laboratory (PML)
  • Marine Biological Association (MBA)
  • Sir Alister Hardy Foundation for Marine Science (SAHFOS)
  • Proudman Oceanographic Laboratory (POL)
  • Scottish Association for Marine Science (SAMS)
  • Sea Mammal Research Unit (SMRU)

Oceans2025 provides funding to three national marine facilities, which provide services to the wider UK marine community, in addition to the Oceans 2025 community. These facilities are:

  • British Oceanographic Data Centre (BODC), hosted at POL
  • Permanent Service for Mean Sea Level (PSMSL), hosted at POL
  • Culture Collection of Algae and Protozoa (CCAP), hosted at SAMS

The NERC-run Strategic Ocean Funding Initiative (SOFI) provides additional support to the programme by funding additional research projects and studentships that closely complement the Oceans 2025 programme, primarily through universities.

What is the programme about?

Oceans 2025 sets out to address some key challenges that face the UK as a result of a changing marine environment. The research funded through the programme sets out to increase understanding of the size, nature and impacts of these changes, with the aim to:

  • improve knowledge of how the seas behave, not just now but in the future;
  • help assess what that might mean for the Earth system and for society;
  • assist in developing sustainable solutions for the management of marine resources for future generations;
  • enhance the research capabilities and facilities available for UK marine science.

In order to address these aims there are nine science themes supported by the Oceans 2025 programme:

  • Climate, circulation and sea level (Theme 1)
  • Marine biogeochemical cycles (Theme 2)
  • Shelf and coastal processes (Theme 3)
  • Biodiversity and ecosystem functioning (Theme 4)
  • Continental margins and deep ocean (Theme 5)
  • Sustainable marine resources (Theme 6)
  • Technology development (Theme 8)
  • Next generation ocean prediction (Theme 9)
  • Integration of sustained observations in the marine environment (Theme 10)

In the original programme proposal there was a theme on health and human impacts (Theme 7). The elements of this Theme have subsequently been included in Themes 3 and 9.

When is the programme active?

The programme started in April 2007 with funding for 5 years.

Brief summary of the programme fieldwork/data

Programme fieldwork and data collection are to be achieved through:

  • physical, biological and chemical parameters sampling throughout the North and South Atlantic during collaborative research cruises aboard NERC's research vessels RRS Discovery, RRS James Cook and RRS James Clark Ross;
  • the Continuous Plankton Recorder being deployed by SAHFOS in the North Atlantic and North Pacific on 'ships of opportunity';
  • physical parameters measured and relayed in near real-time by fixed moorings and ARGO floats;
  • coastal and shelf sea observatory data (Liverpool Bay Coastal Observatory (LBCO) and Western Channel Observatory (WCO)) using the RV Prince Madog and RV Quest.

The data is to be fed into models for validation and future projections. Greater detail can be found in the Theme documents.

Data Activity or Cruise Information


Cruise Name D321 (D321A)
Departure Date 2007-07-24
Arrival Date 2007-08-23
Principal Scientist(s)John T Allen (National Oceanography Centre, Southampton)
Ship RRS Discovery

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:

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

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
B nominal value
Q value below limit of quantification