Metadata Report for BODC Series Reference Number 1341805

• 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.

D365 RRS Discovery Cruise discrete inorganic nutrients sampling document

Cruise details

The Extended Ellett Line is a full-depth hydrographic section between Iceland, 60°N 20°W, Rockall and Scotland. The original Ellett Line across the Rockall Trough was first occupied in 1975 when measurements were attempted four times a year. In 1996 the line was extended to Iceland and since then has been occupied approximately annually. The data form a 35 year time series of the oceanic conditions west of the British Isles. The section monitors the characteristics of the warm water inflow into the Nordic Seas and thence to the Arctic, and observes part of the returning cold water outflow with measurements of the Iceland-Scotland Overflow and the overflow of the Wyville-Thomson Ridge into the Rockall Trough. In total 55 CTD casts were completed during the cruise along the original and Extended Ellett Line, with nutrient samples being taken from the majority of bottles fired on the upcasts.

Originator's data acquisition and processing

The basic water column dissolved nutrients, ammonia, phosphate, silicate (reactive silica) and total oxidized nitrogen (nitrite + nitrate) were analyzed from CTD casts along the Extended Ellett Line. CTD depths for the samples were chosen to correspond with those of the chlorophyll and algal cell count studies down to 200 m and at depths below this corresponding with CFC gas studies. Additional other depths were sometimes chosen to coincide with changes in water mass identified by the TS and dissolved oxygen characteristics from the CTD casts.

Samples were collected in 125 ml acid cleaned polythene bottles directly from the CTD spigots without the use of a tube. Samples were always analyzed within 24 hours of collection and stored in a fridge prior to analysis. Measurement was conducted using a Lachat QuikChem 8500 flow injection autoanalyser using the manufacturers recommended methods: Ammonia, 31-107-06-1-B; Orthophosphate, 31-115-01-1-G; Silicate, 31-114-27-1-A and Nitrate/Nitrite, 31-107-04-1-A.
Samples were measured in triplicate to identify instrument precision. Standards were prepared in deionised water and the samples and standards run in a carrier stream of deionised water. A standard reference solution prepared from nutrient standard solutions supplied by OSIL containing 1µMNH4, 1µMPO4, 10µMSiO2 and 10µMNO3 was run at the start and end of each sample batch to determine analytical accuracy and to adjust for calibration drift during the course of a sample batch analysis.

BODC data processing procedures

Data arrived at BODC in a Microsoft Excel spreadsheet containing 1109 nutrient samples taken during the cruise. The spreadsheet was initially converted into a Comma Separated Values format file (.csv) and appropriate BODC parameter codes were subsequently assigned. The following table shows how the variables supplied were mapped to BODC parameter codes.

Please note: 1109 CTD OTE bottles were fired during 55 CTD casts taken on cruise D365. However, not all of these bottle firings resulted in nutrient samples being taken and/or analysed to produce valid measurements.

Content of data series

The data were loaded from the .csv file into an Oracle database where measurements were linked to corresponding depths through the CTD rosette bottle no. (supplied by the originator) and the CTD rosette bottle no. obtained from electronic Seabird CTD logs (which contained accurate pressure readings for each bottle fired).

Data that lay outside the permitted range for the parameter code were flagged suspect with an 'M' flag by BODC.

Data Quality Report

No problems reported and no significant issues encountered during BODC banking procedures.

Problem Report

No problems reported and no significant issues encountered during BODC banking procedures.

References

Further information can be found in the cruise report cruise report

Project Information

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

Weblink: http://www.oceans2025.org/

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for D365_CTD_CTD25_IB12a

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: