Metadata Report for BODC Series Reference Number 1253252

• 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.

Inorganic nutrient measurements from CTD bottle samples collected during ANDREX cruise JC030

Originator's Protocol for Data Acquisition and Analysis

Water samples for the determination of nitrate and nitrite, phosphate and silicate were drawn from 20 litre Niskin bottles from a 24-rosette sampling system mounted on a Sea-Bird 9/11 plus CTD. The water samples were collected into 35 ml coulter counter vials and kept refrigerated at approximately 4°C until analysis, which usually commenced within 0.5 to 2.0 hours.

Concentrations of nitrate and nitrite, phosphate and silicate were determined by a Skalar SansPlus segmented autoanalyser following methods described by Kirkwood (1996), with the exception that the pump rates through the phosphate line were increased by a factor of 1.5, which improved reproducibility and peak shape. A dilution loop for the sample line of the silicate channel was also installed giving a 2.9 times dilution. This was done in anticipation of the very high silicate concentrations expected in the area to be sampled. Stations were run individually because there was a large gap ca. >8 hours between stations. Further details of the instrumentation setup can be seen in the cruise report.

An artificial seawater matrix (ASW) of 40 g l^-1 sodium chloride was used as the inter-sample 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 by diluting 5 mMol solutions made from weighed dried salts in 1 l of ASW into 1 l plastic volumetric flasks. On setting up the laboratory all labware was washed with 10% HCl and rinsed with MQ water. The wash time and sample time of the autosampler were 90 seconds and the lines were washed daily with 0.5 mol l^-1 sodium hydroxide and 10% Decon 90.

Data processing was undertaken using Skalar proprietary software and was done at regular intervals throughout the cruise. Time series of baseline, instrument sensitivity, calibration curve correlation coefficient, nitrate reduction efficiency and duplicate difference was compiled to check the performance of the autoanalyser over the course of the cruise.

References Cited

Kirkwood, D., 1996. Nutrients: Practical notes on their determinations in seawater. ICES Techniques in marine environmental sciences. 17, 1-25.

BODC Data Processing Procedures

All data were received in one Microsoft Excel format file. Data received were loaded into the BODC database using established BODC data banking procedures. One discrepancy was found between the data originator's metadata and the Sea-Bird .btl files and log sheets. The rosette position numbers 22 and 23 provided for CTD cast 27 were the wrong way round in comparison to the pressure values therefore these were swapped without referral with the data originator. In addition, the following changes were made; all WOCE quality control flags provided by the originator were converted into BODC standard flags, 2 (good) = no flag, 3 (questionable) = 'L', and all absent data values were removed. The data were screened in-house prior to loading. Data were then loaded without any further changes. The following table shows how the variables were mapped to appropriate BODC parameter codes:

Data Quality Report

None (BODC assessment).

Problem Report

None (BODC assessment).

Project Information

Antarctic Deep Water Rates of Export (ANDREX) project document

ANDREX is a UK field programme aimed at investigating the role of the Weddell Gyre in the Meridional Overturning Circulation (MOC) and its influence on deep ocean properties.

The MOC is a critical regulator of Earth's climate and is crucial for deep water ventilation across the globe. Surface currents transport waters towards the poles, where they become dense and sink, flowing equatorward as deep, cool currents. The MOC ensures that the deep oceans remain ventilated and conducive to life, and is also important for anthropogenic carbon sequestration. The southern closure of the MOC in the Weddell Sea is strongly influenced by the Weddell Gyre, which facilitates the exchange of waters between the Antarctic Circumpolar Current (ACC) and the waters of the continental shelf. Cooling and sea ice formation in the Weddell Sea lead to overturning of the water column and the ventilation of Antarctic Bottom Water (AABW), which flows out of the Weddell Sea and into the deep oceans to the north. Thus, the Weddell Gyre plays an important role in the properties of deep ocean waters on a global scale.

The goals of ANDREX are to investigate the exchange of water masses between the ACC and the Weddell Sea, including AABW formation and ventilation rates, carbon and nutrient cycling, the influence of fresh water input from sea ice, precipitation and glacial melt, and the role of the Weddell Gyre in anthropogenic carbon sequestration. The project includes hydrographic, ventilation tracer, biogeochemical and bathymetric measurements along the outer rim of the Weddell Gyre.

ANDREX is funded by the UK Natural Environment Research Council (NERC) Antarctic Funding Initiative (AFI) and involves scientists from the National Oceanography Centre, Southampton (NOC), the British Antarctic Survey (BAS), the University of East Anglia (UEA), the University of Manchester, the Alfred Wegener Institut (AWI) and the Woods Hole Oceanographic Institution (WHOI).

For more information please see the official project website at ANDREX

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for JC030_CTD_CTD15

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.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

World Ocean Circulation Experiment (WOCE) Southern Repeat Section 4

WOCE established a repeat hydrographic section across Northern Weddell sea and designated it SR04. The section is located between Antarctic Peninsula and south of South Africa within a bounding box of -44.00583, -53.624 (North-Western corner) and -71.02167, 38.99683 (South-Eastern corner).

A table of cruises which have occupied SR04 is presented below with links to the relevant cruise reports or cruise narratives (where available).

Related Fixed Station activities are detailed in Appendix 2

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: JC030_CTD_CTD15

Related series for this Data Activity 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.

Appendix 2: WOCE Southern Repeat Section 4

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.