Metadata Report for BODC Series Reference Number 1895231

• 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

Seal Analytical AutoAnalyzer 3HR

The model AA3 is an upgrade from Seal Analytics AutoAnalyzer II and is specifically designed for colorimetric determination of dissolved nutrients in environmental smaples. This model fully automates repetitive and complex sample analysis and can perform solvent extractions, distillation, gas diffusion, on-line filtration and in-line UV digestion in a continuously flowing stream.

It has a modular design which can integrate a sampler, pump, chemistry test module and photometer. It also accepts Multitest Manifolds designed to extend any size analyzer to a multiple chemistry system capable of dual range of tests which, in turn, eliminate the need to change manifolds and filters when changing tests.

The AA3 uses segmented flow analysis principles to reduce inter-sample dispersion, it can analyse up to 100 samples per hour using stable LED light sources. It also contains glass coils, which allow for chemically inert and easy visual checks.

The available modules are:

• Digital colorimeter: bubble through the flow cell to increase sampling rate and true Dual beam operation with continuous real-time referencing
• High Precision Pump: multi-speed motor, electronic air injection, optional valves for auto reagent switching and a buil in leak detector
• Multitest Manifold: allows for up to 16 different analyses
• Chemistry Module: glass coils which are chemically inter and allow for clear view of the flow, gas difusion or dialysis options
• XY2/XY3: high capacity random access sampler, up to 180/270 samples in cups or tubes in 2/3 racks, separate rack for standards, optional integrated pump and auto-diluter
• Distillation Module: automatic in line distillation when required before colorimetric analysis

Further information can be found in the manufacturer's brochure.

Niskin Bottle

The Niskin bottle is a device used by oceanographers to collect subsurface seawater samples. It is a plastic bottle with caps and rubber seals at each end and is deployed with the caps held open, allowing free-flushing of the bottle as it moves through the water column.

Standard Niskin

The standard version of the bottle includes a plastic-coated metal spring or elastic cord running through the interior of the bottle that joins the two caps, and the caps are held open against the spring by plastic lanyards. When the bottle reaches the desired depth the lanyards are released by a pressure-actuated switch, command signal or messenger weight and the caps are forced shut and sealed, trapping the seawater sample.

Lever Action Niskin

The Lever Action Niskin Bottle differs from the standard version, in that the caps are held open during deployment by externally mounted stainless steel springs rather than an internal spring or cord. Lever Action Niskins are recommended for applications where a completely clear sample chamber is critical or for use in deep cold water.

Clean Sampling

A modified version of the standard Niskin bottle has been developed for clean sampling. This is teflon-coated and uses a latex cord to close the caps rather than a metal spring. The clean version of the Levered Action Niskin bottle is also teflon-coated and uses epoxy covered springs in place of the stainless steel springs. These bottles are specifically designed to minimise metal contamination when sampling trace metals.

Deployment

Bottles may be deployed singly clamped to a wire or in groups of up to 48 on a rosette. Standard bottles and Lever Action bottles have a capacity between 1.7 and 30 L. Reversing thermometers may be attached to a spring-loaded disk that rotates through 180° on bottle closure.

DY040 inorganic nutrient data from CTD bottles

Originator's Protocol for Data Acquisition and Analysis

The following information and more detail can be found in the cruise report.

A 5-channel and 2-channel Seal Analytical AA3 autoanalyser were set up for the analysis of micro-molar concentrations of dissolved inorganic nutrients (silicate, nitrate, phosphate, nitrate+nitrite) and total nutrients (total dissolved phosphorus and total dissolved nitrogen). Samples were collected directly into 15 ml plastic centrifuge tubes which were rinsed three times before drawing the sample. The tubes were stored at 4°C before analyses were carried out.

BODC Data Processing Procedures

Data received were loaded into the BODC database using established BODC data banking procedures. Date were loaded into BODC's database without any changes.

Parameters were mapped to BODC parameter codes as follows:

Data Quality Report

NO₃+NO₂, Total Dissolved Phosphorus (TDP) and NH₄ channels malfunctioned during calibration. Seal analytical was contacted and advice was received. Photometers within the colorimeter were swabbed, lamp connections and lamps were swapped - This did not improve the problem. It was found that the TDP channel did not produce stable flow and therefore stable baseline for analysis. The colourimeter of the NO₃+NO₂ and NO₂ channels was swapped with that of the Total Dissolved Nitrogen (TDN) and TDP channels resulting in the loss of one channel from the working colorimeter. The NO₂ channel was 'sacrificed' and the working side of each colorimeter was used to measure NO₃+NO₂ and total nitrogen respectively. The NH₄ channel was used until cast 43.

There were negative Nitrate values which have been flagged as improbable by BODC.

Project Information

NOCS National Capability

The National Oceanography Centre Southampton National Capability focuses on long term science concerned with basin/decadal variability of the Ocean.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for DY040_CTD_CTD_040

Please note:the supplied parameters may not have been sampled from all the bottle firings described in the table above. Cross-match the Sample Reference Number above against the SAMPRFNM value in the data file to identify the relevant metadata.

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

24.5 degrees N Hydrographic Transatlantic section - A05

The hydrographic transatlantic section at 24.5 degrees North has been occupied 8 times, namely in 1957, 1981, 1992, 1998, 2004, 2010, 2015 and 2020. The section is an attempt to calculate the transports of water and its constituents (heat, salinity, nutrients, biological productivity) along this latitude, and to compare the data so that the degree of change in the North Atlantic transports can be revealed. The Hydrographic Programme of the international World Ocean Circulation Experiment (WOCE) designated this section as A05. Since WOCE, the section occupations contribute to the Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP).

Map of stations

The station positions for most of the occupied sections are shown in the above figures. Sections occupied in 1957, 1981, 1992, 1998 and 2004 are shown in the upper figure. The section occupied in 2010 is shown in the lower figure.

The 1957 and 1992 sections each went zonally along 24.5 degrees N from the African coast to the Bahama Islands. Because of diplomatic clearance issues, the 1981, 1998, 2004, 2010 and 2015 sections angled southwestward from the African coast at about 28 degrees N to join the 24.5 degrees N section at about 23 degrees W. The 1998, 2004 and 2010 sections angled northwestward at about 73 degrees W to finish the section along 26.5 degrees N. The 2010 and 2020 sections deviated from the previous sections across the Mid-Atlantic Ridge (MAR) in order to sample the deepest channel and capture the passage of the deep water across the MAR.

Table 1: Occupations of the section

References

Baringer, M. O. N. and R. L. Molinari, 1999. Atlantic Ocean baroclinic heat flux at 24 to 26°N. Geophysical Research Letters, 26, 353-356.

Bryden, H. L., H. R. Longworth, and S. Cunningham, 2005b. Slowing of the Atlantic meridional overturning circulation at 25°N. Nature, 438, 655-657.

Fuglister, F. C., 1960. Atlantic Ocean Atlas of Temperature and Salinity Profiles and Data from the International Geophysical Year of 1957-1958. Vol. 1, Woods Hole Oceanographic Institution Atlas Series, WHOI, Woods Hole, Massachusetts.

King, B. A. et al., 2012. RRS Discovery Cruise 346, 05 Jan-19 Feb 2010. The 2010 transatlantic hydrography section at 24.5N. Southampton, UK, National Oceanography Centre Southampton, 177pp. (National Oceanography Centre Cruise Report, No. 16).

King, B. A. et al., 2016. RRS Discovery Cruise DY040 (RAGNARoCC), 06 Dec 2015 - 22 Jan 2016. The 2015 transatlantic hydrography section at 24.5N. Southampton, UK, National Oceanography Centre Southampton, 159pp. (National Oceanography Centre Cruise Report).

Parilla, G., A.Lavin, H. Bryden, M. Garcia, and R. Millard, 1994. Rising temperatures in the subtropical North Atlantic Ocean over the past 35 years. Nature, 369, 48-51.

Roemmich, D. and C. Wunsch, 1985. Two transatlantic sections: meridional circulation and heat flux in the subtropical North Atlantic Ocean. Deep Sea Research, 32, 619-664.

Sanchez-Franks, A., 2020. RRS James Cook Cruise JC191, 19 January - 1 March 2020. Hydrographic sections from the Florida Straits to the Canaries Current across 24N in the Atlantic Ocean. Southampton, UK, National Oceanography Centre Southampton, 262pp. (National Oceanography Centre Cruise Report, No. 70).

Related Fixed Station activities are detailed in Appendix 1

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: 24.5 degrees N Hydrographic Transatlantic section - A05

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.