Metadata Report for BODC Series Reference Number 1307558

• 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.

Dissolved inorganic nutrients from CTD bottles collected during NABOS/CABOS cruise NABOS2007 as part of the ASBO project

Originator's Protocol for Data Acquisition and Analysis

Seawater samples were taken from a CTD-rosette sampling system mounted on a lowered Seabird Electronics SeaCAT Profiler SBE19plus. The CTD was not on a conducting wire, so an auto-fire module was used to fire the bottles while the rosette was in motion. The CTD data at the time of firing were unusable for the uppermost bottles, as the sensors did not have time to stabilise after entering the water, and the pump wasn't yet on. Water samples were collected using five liter Niskin bottles which were fired on the downcast, this worked as the ship was in relatively warm, ice-free conditions. The firing depths were pre-programmed and all bottles were fired whilst the rosette was in motion, therefore the pressure recorded by the CTD was approximate. The pressures were processed by taking the median of the data from between 1 scan before and 2 scans after the firing time (the CTD measures at 4 Hz). The CTD pressure for the bottle firing times were interpolated at the time of firing minus 0.75 dbar. The offset was applied to take into account the height difference between the pressure sensor and bottles.

Seawater was collected for the analysis of dissolved inorganic nutrients, dissolved oxygen, barium, δ¹⁸O, and salinity. Dissolved oxygen, barium, δ¹⁸O, and salinity have been loaded separately. Samples were taken from 44 CTD casts.

Seawater samples were collected in 30 mL plastic pots for the analysis of nitrate and nitrite (NO₃ ^- and NO₂ ^-), phosphate (PO₄ ^3-), and silicate (Si(OH)₄). Pots were rinsed three times with seawater before collection. Five mM stock standard solutions prepared in Milli-Q water were used to produce working standards. Working standards were prepared in a saline solution (40 g NaCl L^-1 of Milli-Q water) which was also used as a diluent for the analysis. Analysis runs consisted of a set of calibration standards, wash and drift cups, certified low-nutrient seawater (in order to test for contamination of the saline solution), and samples. Given the ship's lack of a Milli-Q system, 350 L of ultra pure (Milli-Q) water for general lab use was brought from the NOCS (UK) in 25 L acid-washed (15% HCl) carboys. The standards used can be found on page 73 of thecruise report. Analyses were carried out within 30 minutes of sample collection using a segmented continuous-flow Skalar Sanplus autoanalyser set up for analysis and data logging with the Flow Access Software version 1.3.11. The detection limits of the instrument were 0.03 µmol for phosphate, 0.2 µmol for nitrate and 0.3 µmol for silicate, values below these were flagged and set to zero.

Instrumentation

BODC Data Processing Procedures

A total of 503 (nitrate), 496 (phosphate) and 503 (silicate) bottle sample data from 46 CTD casts were received in an excel file. Data received were loaded into the BODC database using established BODC data banking procedures. All values identified below the instrument detection limits were flagged as such. Those values identified by the originators had been set to zero and those values identified by BODC were set to the detection limit. 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

Arctic Synoptic Basin-Wide Oceanography (ASBO) project document

ASBO is an International Polar Year (IPY) consortium project aimed to improve the knowledge of the functioning of the Arctic sea-ice-ocean system.

Coupled climate models predict a rate of warming in the Arctic some 2-3 times higher than the global average. One consequence of this warming is a change in the Arctic freshwater storage and transport, both within the Arctic, and through gateways to the world's oceans. Models and palaeoceanographic data show that increased freshwater input from the Arctic to the North Atlantic can "distress" the thermohaline circulation. A decrease in the North Atlantic overturning may lead to a cooling of Northern Europe, so the understanding of these changes is one of the highest priorities for UK and NERC science. However, the understanding of the mechanisms by which the freshwater input to the Arctic is transformed, stored, and exported is currently based on fragmentary observations, and poorly constrained models. By combining the data gathered during IPY with historical and satellite data, ASBO will use state-of-the-art numerical models to provide new quantitative estimates of the storage and transport of fresh water in the Arctic both for the present, recent past and next century.

The ASBO project comprises of a combination of fieldwork, remote sensing and a hierarchy of modelling approaches including; 1) The deployment of ice-tethered platforms and ice mass balance buoys, to take water samples for chemical and isotope analysis, and to make ocean turbulence profiles. 2) The analysis of remote-sensed data from the Envisat satellite in order to elucidate interannual changes in Arctic sea ice mass and in sea surface height. 3) A modelling hierarchy beginning with an inverse model of Arctic ocean boundary exchanges with adjacent basins; use of an assimilation model to achieve a best estimate of the state and evolution of the Arctic Ocean; and results from a high-resolution (1/12 degree) sea-ice-ocean general circulation model, forced with a realistic atmosphere, used to aid in the interpretation of observations and the description of potentially new features of the Arctic circulation.

ASBO will participate in three Arctic expeditions in total; two expeditions to the Siberian margin on Russian vessels, in collaboration with the Nansen and Amundsen Basin Observing System (NABOS) and the Canadian Basin Observational System (CABOS) project with the International Arctic Research Center and University of Alaska Fairbanks, USA (IARC-UAF), and one to the Canadian Basin on a Canadian vessel, in collaboration with the Beaufort Gyre Exploration Project CCGS. Turbulence measurements and chemical sampling will be carried out during the Siberian expeditions on cruises NABOS2007 between 07 September 2007 and 17 October 2007 and cruise NABOS2008 between 02 October 2008 and 30 October 2008. Ice-tethered profilers and ice mass balance buoys will be deployed during the Canadian Basin expedition on cruise Louis S. St-Laurent JOIS2008 between 17 July 2008 and 19 August 2008.

ASBO is funded by the UK Natural Environment Research Council (NERC) and involves the collaboration of a number of UK institutions: University College London, The National Oceanography Centre, University of Reading, Scottish Association for Marine Science, Bangor University and NERC British Antarctic Survey. The period of the project funding is from 01 June 2007 to 31 March 2012 and the principal investigator is Dr SW Laxon from the University College London, Mullard Space Science Laboratory.

For more information please see the National Oceanography Centre project website.

Data Activity or Cruise Information

Data Activity

BODC Sample Metadata Report for NABOS2007_CTD_CTD48

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: