Metadata Report for BODC Series Reference Number 1273738

• 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

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.

RV Poseidon Cruise PO314 Discrete inorganic nutrient (nitrate, silicate and phosphate) concentrations from CTD bottles

Cruise Details

Content Of Data Series

Originator's Data Acquisition and Processing

Sampling Strategy

The cruise was designed to repeat the hydrographic section from Scotland to Rockall, called the Ellett Line, and its extension to Iceland. 73 stations were worked with CTD and lowered ADCP and sampled for chemical (macro- nutrients and dissolved oxygen) and biological (chlorophyll a) analyses. Depths of the CTD profiles ranged from 27m to 2685m. At shallow stations (~100m depth) Niskin bottles were typically fired at ~3 depths. For deeper stations 2 bottles were fired at the bottom, 3 to 4 bottles in the upper mixed layer and the others at regularly spaced or targeted intervals in the profile.

Instrumentation and Methodology

A total of 73 CTD casts were completed on the cruise, using a 12-way frame arrangement from which CTD bottle samples were taken with the following equipment:

Sea-Bird 9/11+ CTD
Sea-Bird 12 position Carousel
12 by 10L General Oceanics Niskin bottles

Inorganic nutrient measurements from each bottle were derived as follows:
Analysis for nitrate + nitrite (hereinafter nitrate), phosphate and silicate was undertaken on a Skalar Sanplus autoanalyser following methods described by Kirkwood (1996) with the exception that the pump rates through the phosphate line are increased by a factor of 1.5 which improves reproducibility and peak shape. Samples were drawn from 10 L Niskin bottles into 25ml sterilin coulter counter vials and kept refrigerated at 4°C until analysis which commenced within 24 hours. Stations were run in batches of 4-8 depending on sampling frequency regulated by depth of station. Stations were generally run in batches of 4-7 with most runs containing 4 or 5 stations. In total 73 stations were sampled over an 11 day period requiring 12 runs to be undertaken on the autoanalyser, with a total of 722 samples being analysed (not including standards, blanks or replicates).
An artificial seawater matrix (ASW) of 40 g/l sodium chloride was used as the intersample wash and standard matrix. The nutrient free status of this solution was checked by running Ocean Scientific International (OSI) nutrient free seawater on every run. A single set of mixed standards were made up at the start of the cruise and used throughout the cruise, new standards were made as and when they were needed. These were made using OSI nutrient standard solutions (Nitrate and Silicate, 1000 µm; phosphate, 100 µm) by diluting the solutions with ASW into 250 mL plastic volumetric flasks that had been cleaned by soaking for 6 weeks in MQ water. Standards used were 20, 10, 5 µm for nitrate and silicate and 2, 1, 0.5 µm for phosphate. This was in an effort to minimise the run to run variability in concentrations observed on previous cruises. An OSI nutrient standard solution of 10 µm nitrate and silicate and 1 µm phosphate was made fresh every two days and run routinely after every 15-20 samples to monitor the analytical drift and to ascertain the accuracy of the technique along with monitoring the potential degradation of the standards over the 12 day period. The efficiency of the Cd reduction column was monitored by running a nitrite standard every run. Initially a standard of 10 µm was made but this appeared to have degraded after only three days giving greater than 100% efficiency. Due to the limited amount of Nitrite stock (100 µm, 50 mL) a standard of 2 µm was made fresh every other day to monitor the column efficiency, this approach was successful giving an efficiency close to 100% with no degradation.

Further information about data quality can be found on p.33 of the cruise report.

Data Processing

Data processing was undertaken using Skalar propriety software.

BODC Data Processing

Data arrived at BODC in the form of Pstar files generated by the established Seabird CTD data processing routines. These files were converted into a single Comma Separated Value (csv) format file in Microsoft Excel. The data were then loaded into the BODC database using established BODC data banking procedures. The source files were the most processed and accurate version of the data, and these data were uploaded to an sqlplus table which included the following headings:

Data Quality Report

Please refer to p.33 of the cruise report.

Problem Report

None

BODC Quality Control Flags

No quality control flags applied to this dataset by either the data originator or BODC.

Cruise Summary

RV Poseidon cruise 314 set out to occupy the 'Extended Ellett Line' Scotland - Rockall - Iceland time series. The objectives of doing so were:
1. To observe water mass properties, the instantaneous velocity field and subsequently the heat and salt (freshwater) fluxes between the subpolar gyre and the Nordic Seas in 2004.
2. To compare the 2004 conditions with those observed in the previous years (to 1975 in Rockall Trough, 1988 in the Iceland Basin), quantifying the interannual to decadal changes in properties and understanding the causal mechanisms of variability.
3. To enhance the physical and tracer measurements with biological observations to investigate nutrient cycling, export production, ecosystem structure and dynamics.

Project Summary

Oceans 2025 is a five-year programme, funded by the Natural Environment Research Council (NERC). It is designed by and implemented through seven leading UK marine centres. Oceans 2025 addresses some key challenges that the UK faces as a result of a changing marine environment. It will increase our understanding of the size, nature and impacts of these changes and will:

• improve our knowledge of how the seas behave, not just now but in the future;
• help to 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.

The marine centres are working together in coordination and will also be supported by cooperation and input from government bodies, universities and other partners.For more information on this project, please go to the Oceans 2025 website.

Extended Ellett Line

The Extended Ellett Line is a time series of CTD stations which monitors the N. E. Atlantic current extension through the Iceland Basin, the recirculation of the eastern subpolar gyre and the Iceland Scotland overflow. It is an extension of the Ellett Line time series first occupied in 1975. The Extended Ellett Line consists of 57 standard stations which run from Scotland through Rockall and from Rockall to Iceland. Measurements at these stations or close to these stations lie within a box bounded by co-ordinates 56° 40.02'N, 020° 00.00'W at the southwest corner and 63° 17.52'N, 006° 07.98'W at the northeast corner.

The time series is maintained by the Scottish Association for Marine Science (SAMS) and the National Oceanography Centre, Southampton (NOC). Funds for the NOC and SAMS efforts are provided by the Natural Environment Research Council. Additional sections are periodically carried out by the Fisheries Research Services at Marine Laboratory, Aberdeen. The Ellett Line time series is part of the UK climate monitoring strategy, with core funding provided by government agencies. Additional funding is periodically obtained by the participating institutes to carry out detailed research into particular aspects of the section and the region.

For further details, please see the Extended Ellett Line website.

References

(1) Kirkwood, D (1996) Nutrients: Practical notes on their determination in sea water. ICES techniques in marine environmental sciences. No. 17, 25pp.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for PO314_CTD_CT314404

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

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: