Metadata Report for BODC Series Reference Number 1269395


Metadata Summary

Data Description

Data Category Water sample data
Instrument Type
NameCategories
Niskin bottle  discrete water samplers
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator Dr Sinhue Torres-Valdés
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) ANDREX
 

Data Identifiers

Originator's Identifier JR20100319_CTD_NUTS_570:CTD98
BODC Series Reference 1269395
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-04-20 05:09
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 55.21520 S ( 55° 12.9' S )
Longitude 34.50799 W ( 34° 30.5' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 7.4 m
Maximum Sensor Depth 544.7 m
Minimum Sensor Height 5.3 m
Maximum Sensor Height 542.6 m
Sea Floor Depth 550.0 m
Sensor Distribution Unspecified -
Sensor Depth Datum Unspecified -
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODE Rank Units Short Title Title
ADEPZZ01 1 Metres DepBelowSurf Depth below surface of the water body
BOTTFLAG 1 Dimensionless C22_flag Sampling process quality flag (BODC C22)
NTRZAATX 1 Micromoles per litre NO3+NO2_Unfilt_ColAA Concentration of nitrate+nitrite {NO3+NO2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
PHOSAATX 1 Micromoles per litre PO4_Unfilt_ColAA Concentration of phosphate {PO43- CAS 14265-44-2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
ROSPOSID 1 Dimensionless RosPos Bottle rosette position identifier
SAMPRFNM 1 Dimensionless SampRef Sample reference number
SLCAAATX 1 Micromoles per litre SiOx_Unfilt_ColAA Concentration of silicate {SiO44- CAS 17181-37-2} per unit volume of the water body [dissolved plus reactive particulate phase] by colorimetric autoanalysis
 

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

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 have a capacity between 1.7 and 30 L, while Lever Action bottles have a capacity between 1.7 and 12 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 cruise JR20100319 (JR235, JR236, JR239)

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 (s/n 09P-0869). Casts 1-68 were part of the ANDREX project and casts 70-98 were part of the BAS Polar Oceans strategic research programme. Some bottles were leaking badly and were excluded from any sampling. Over the course of the cruise, the bottles had a success rate of 89% (judged by successful closure and non-leakage). This rate was markedly lower towards the start of the cruise before work was undertaken during the cruise to help improve the success rate. Please see the cruise report which provides further information about the bottle problems and summarises the modifications made to the Niskin bottles.

Water samples from the Niskin bottles were collected directly into 30 mL plastic pots. Pots were rinsed with sample water at least three times before drawing the sample. Samples were stored in a fridge at approximately 4 °C until sampling for two or three stations were completed. Analyses were thus carried out for typically 2-3 stations at a time. This was done in order to avoid excess production of waste, given that waste was to be returned to the UK.

Most analyses were started within 2-12 hours of sample collection using a segmented continuous-flow Skalar SansPlus autoanalyser set up for analysis and data logging with the Flow Access Software version 1.3.11 following Kirkwood (1996), with the exception that the pump rates through the phosphate line were increased by a factor of 1.5, which improves reproducibility and peak shape. A dilution loop for the silicate channel was also installed giving a 2.9 times dilution. This was done in anticipation of the high silicate concentrations typical of the Southern Ocean. All labware was washed with 10% HCl and rinsed with MQ water previous to the cruise and several times before use once onboard. The autoanalyser was washed through with 10% Decon 90 then Milli-Q water for at least 15-30 minutes each after each run when the time between stations allowed, otherwise the autoanalyser was left with the reagent tubing connected ready for the next run. New pump tubing and lamps were fitted at the start of the cruise, along with a new cadmium column. All tubing was turned around on the 8th of April 2010 and the cadmium column was replaced (from run 25). The analysis was calibrated using a set of five standards. Approximately 5 mMol L -1 of 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 in 1 L of Milli-Q water, artificial seawater), which was also used as a diluent for the analysis. New batches of artificial seawater were prepared almost once every 2 weeks. These were analysed prior to being used in order to check for contamination and consistency. Certified Ocean Scientific International (OSIL) Low Nutrient Seawater (LNSW) was measured in duplicate in every run in order to test artificial seawater for contamination.

LNSW was also used as a quality control in order to check for the reproducibility of low nutrient concentrations. The performance of the autoanalyser was monitored by producing time series plots of the following parameters: standards concentration, baseline, calibration slope (instrument sensitivity), calibration correlation coefficient, nitrate reduction efficiency, low nutrient seawater and certified standards. The precision of the method was determined by monitoring the variations of the complete set of standards measured throughout the cruise. Triplicate analyses were performed on the first and last sample of every station, plus in a randomly selected sample for most station. These showed the sample variability of replicates from a given mean concentration was in general <0.5%, <0.3% and <0.5% for nitrate, silicate and phosphate respectively. The limits of detection of this method were estimated as twice the standard deviation of the concentration of lowest standard of each nutrient. The limits of detection of this method during were 0.01 mmol L -1 for Phosphate, 0.13 mmol L -1 for nitrate+nitrite and 0.15 mmol L -1 for silicate. Further information about the standards used can be found in the cruise report .

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 csv formatted file and were loaded into the BODC database using established BODC data banking procedures. 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:

Originator's Parameter Unit Description BODC Parameter Code BODC Unit Comments
EXPOCODE - Cruise - - -
CASTNO - CTD station number - - -
SAMPNO - Sample number - - Null values only
DATE - Year - - -
TIME - Time - - Null values only
LATITUDE - Latitude - - -
LONGITUDE - Longitude - - -
CTDPRS dbar CTD pressure - - -
CTDPRS_FLAG_W - CTD pressure flags - - Null values only
BTLNBR - Rosette position - - -
BTLNBR_FLAG_W - Bottle flags - - Null values only
Depth m Depth - - Null values only
Depth_FLAG_W - Depth flags - - Null values only
temp - CTD temperature - - -
temp_FLAG_W - CTD temperature flags - - Null values only
potemp - CTD potential temperature - - -
potemp_FLAG_W - CTD potential temperature flags - - Null values only
sal_cal - CTD salinity - - -
sal_cal_FLAG_W - CTD salinity flags - - Null values only
NO3 µmol l -1 Nitrate+nitrite NTRZAATX µmol l -1 -
NO3_FLAG_W - Nitrate+nitrite flags - - -
SiO4 µmol l -1 Silicate SLCAAATX µmol l -1 -
SiO4_FLAG_W - Silcate flags - - -
PO4 µmol l -1 Phosphate PHOSAATX µmol l -1 -
PO4_FLAG_W - Phosphate flags - - -
oxy_cal µmol l -1 CTD oxygen - - -
oxy_cal_FLAG_W - CTD oxygen flags - - -
NO3 µmol kg -1 Nitrate+nitrite - - Nitrate+nitrite in µmol l -1 units loaded
NO3_FLAG_W - Nitrate+nitrite flags - - -
SiO4 µmol kg -1 Silicate - - Silicate in µmol l -1 units loaded
SiO4_FLAG_W - Silicate flags - - -
PO4 µmol kg -1 Phosphate - - Phosphate in µmol l -1 units loaded
PO4_FLAG_W - Phosphate flags - - -

Data Quality Report

All WOCE quality control flags provided by the originator were converted into BODC standard flags, 2 (good) = no flag, 3 (questionable) and 4 (bad) = 'L', and all absent data values were removed. No further flags were added by BODC.

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

Start Date (yyyy-mm-dd) 2010-04-20
End Date (yyyy-mm-dd) 2010-04-20
Organization Undertaking ActivityBritish Antarctic Survey
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierJR20100319_CTD_CTD98
Platform Categorylowered unmanned submersible

BODC Sample Metadata Report for JR20100319_CTD_CTD98

Sample reference number Nominal collection volume(l) Bottle rosette position Bottle firing sequence number Minimum pressure sampled (dbar) Maximum pressure sampled (dbar) Depth of sampling point (m) Bottle type Sample quality flag Bottle reference Comments
804716   20.00 1    551.20  552.20  545.30 Niskin bottle No problem reported    
804719   20.00 2    550.60  551.60  544.70 Niskin bottle No problem reported    
804722   20.00 3    506.20  507.20  500.80 Niskin bottle No problem reported    
804725   20.00 4    505.30  506.30  499.90 Niskin bottle No problem reported    
804728   20.00 5    455.70  456.70  450.90 Niskin bottle No problem reported    
804731   20.00 6    455.60  456.60  450.80 Niskin bottle No problem reported    
804734   20.00 7    405.30  406.30  401.00 Niskin bottle No problem reported    
804737   20.00 8    406.00  407.00  401.70 Niskin bottle No problem reported    
804740   20.00 9    354.40  355.40  350.70 Niskin bottle No problem reported    
804743   20.00 10    354.60  355.60  350.90 Niskin bottle No problem reported    
804746   20.00 11    304.80  305.80  301.60 Niskin bottle No problem reported    
804749   20.00 12    304.00  305.00  300.80 Niskin bottle No problem reported    
804752   20.00 13    203.10  204.10  201.00 Niskin bottle No problem reported    
804755   20.00 14    152.90  153.90  151.30 Niskin bottle No problem reported    
804758   20.00 15    153.20  154.20  151.60 Niskin bottle No problem reported    
804761   20.00 16    102.50  103.50  101.30 Niskin bottle No problem reported    
804764   20.00 17    102.40  103.40  101.20 Niskin bottle No problem reported    
804767   20.00 18     77.00   78.00   76.10 Niskin bottle No problem reported    
804770   20.00 19     77.60   78.60   76.70 Niskin bottle No problem reported    
804773   20.00 20     52.10   53.10   51.40 Niskin bottle No problem reported    
804776   20.00 21     51.60   52.60   50.90 Niskin bottle No problem reported    
804779   20.00 22     27.00   28.00   26.60 Niskin bottle No problem reported    
804782   20.00 23      7.70    8.70    7.40 Niskin bottle No problem reported    
804785   20.00 24      7.70    8.70    7.40 Niskin bottle No problem reported    

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

Cruise Name JR20100319 (JR235, JR236, JR239)
Departure Date 2010-03-19
Arrival Date 2010-04-24
Principal Scientist(s)Mike Meredith (British Antarctic Survey)
Ship RRS James Clark Ross

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:

Flag Description
Blank Unqualified
< Below detection limit
> In excess of quoted value
A Taxonomic flag for affinis (aff.)
B Beginning of CTD Down/Up Cast
C Taxonomic flag for confer (cf.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
I Taxonomic flag for single species (sp.)
K Improbable value - unknown quality control source
L Improbable value - originator's quality control
M Improbable value - BODC quality control
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain