Metadata Report for BODC Series Reference Number 1632368

• 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.

AMT4 Nutrient (micromolar) measurements from CTD bottle samples

Originator's Protocol for Data Acquisition and Analysis

This data originates from analyses of bottle samples taken from 35 CTD casts.

The nutrient samples were generally collected from the second cast of the day. The concentrations of nutrients were measured colourimetrically using a 4-channel, Technicon auto-analyser with standard methodologies. All depths from the CTD (typically 10) were measured on each cast, generally within 2 hours of collection. Surface samples were not taken from the pumped supply. A total of 35 casts were analysed, 7 of the casts were to depths of 1000m on this voyage, whereas previously maximum depths achieved were of the order 200m.

All samples were analysed on board within hours of collection and the data processed to calibrated and salinity corrected digital values. The overall patterns were very similar to previous AMT transects. Total nitrogen was only detectable in the surface waters south of Montevideo and north of 47oN. Through the tropics and between these positions, total nitrogen was below detection in the surface waters but could be measured in samples from below the thermocline. Although the value of macro-nutrients measured in surface waters are of limited value to biogeochemical studies when the values fall below detection, the data from depth is still useful in the interpretation of primary production. The last four AMT cruises have all been analysed using the same instrument and identical standardisation procedures. Maximum values for all three nutrients were not large during AMT1 because sampling depths tended to be shallower then. However, a plot of the ratio of total nitrogen (µmol N) to total P (µmol P) obtained on each survey show that all four previous cruises returned similar ranges of values and that the ratios were reasonably consistent. AMT4 data fell within an envelope of all the previous AMT nutrient data when plotted in this way, which provides a measure of confidence in the data.

References Cited

Instrumentation Description

Not relevant to this data set.

BODC Data Processing Procedures

Data were submitted to BODC in Microsoft Excel spreadsheet format and saved to the BODC archive with reference PML010014. Sample metadata were checked against information held in the database. Originator's sample ID was matched based on latitude/longitude and bottle firing depth. Station/Sample reference provided is the Julian Day (JD) and the cast that sampling took place on. These were matched to the CTD casts that took place each day on the cruise.

OIDs were present in the database for the CTD events in the format CTDPxxx, where xxx was the cast number for the cruise. CTDP049 (137c) had four depths in the originator's file (700, 800, 900 and 1000 m) that were not listed in the cruise report as depths at which bottles were fired. The data was loaded linked to the depths in the cruise report (800, 1000, 1500 and 2000 m).

There were replicate samples provided for one depth on a number of casts. The mean of the replicates were taken for each depth and the values entered into the database for the following samples.

There was an unlabelled cast of data in the originator's file, which could not be loaded to the database. The nitrite sample at 175 m from CTD014 (122a) was below the detection limit but the detection limit has not been specified.

Parameter codes defined in BODC parameter dictionary were assigned to the variables. The data were assigned parameter codes defined in BODC parameter dictionary. Data loaded into BODC's database using established BODC data banking procedures.

A parameter mapping table is provided below;

Data Quality Report

BODC has not been advised of any quality checks carried out by the data originator. BODC has highlighted negative values with the BODC 'M' flag for suspect data.

Problem Report

Not relevant to this data set.

Project Information

The Atlantic Meridional Transect (AMT) - Phase 1 (1995-2000)

Who was involved in the project?

The Atlantic Meridional Transect (AMT) programme was designed by and implemented as a collaboration between Plymouth Marine Laboratory (PML) and Southampton Oceanography Centre (SOC). The programme was hosted by Plymouth Marine Laboratory and involved additional researchers from UK and international universities throughout its duration.

What was the project about?

When AMT began in 1995 the programme provided a platform for international scientific collaboration, including the calibration and validation of SeaWiFs measurements and products. The programme provided an exceptional opportunity for nationally and internationally driven collaborative research and provided a platform for excellent multi-disciplinary oceanographic research. As an in situ observation system, the data collected by the AMT consortium informed on changes in biodiversity and function of the Atlantic ecosystem during this period of rapid change to our climate and biosphere.

The scientific aims were to assess:

• mesoscale to basin scale phytoplankton processes
• the functional interpretation of bio-optical signatures
• the seasonal, regional and latitudinal variations in mesozooplankton dynamics

When was the project active?

The first phase of the AMT programme ran from 1995 to 2000 and consisted of a total of 12 cruises. A second phase of funding allowed the project to continue for the period 2002 to 2006 with a further 6 cruises.

Brief summary of the project fieldwork/data

The AMT programme undertook biological, chemical and physical oceanographic research during the annual return passage of the RRS James Clark Ross between the UK and the Falkland Islands or the RRS Discovery between the UK and Cape Town, a distance of up to 13,500 km. This transect crossed a range of ecosystems from sub-polar to tropical and from euphotic shelf seas and upwelling systems to oligotrophic mid-ocean gyres. The transect route was covered north-south in September/October and south-north in April/May of each year.

The measurements of hydrographic and bio-optical properties, plankton community structure and primary production completed on the first 12 transects (1995-2000) represent the most coherent set of repeated biogeochemical observations over ocean basin scales. This unique dataset has led to several important discoveries concerning the identification of oceanic provinces, validation of ocean colour algorithms, distributions of picoplankton, identifying new regional sinks of pCO2 and variability in rates of primary production and respiration.

Who funded the project?

The programme was funded by the Natural Environment Research Council (NERC) and further support was received from the National Aeronautics and Space Administration (NASA) with equipment and funding from the Sea-viewing Wild Field-of-view Sensor (SeaWiFS) project.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for AMT4_CTD_CTDP010

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

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:

Appendix 1: AMT4_CTD_CTDP010

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.