Metadata Report for BODC Series Reference Number 1335640


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 Mr Mark Stinchcombe
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) -
 

Data Identifiers

Originator's Identifier JC031_CTD_NUTS_257:CTD_079
BODC Series Reference 1335640
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2009-02-26 03:57
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 54.66668 S ( 54° 40.0' S )
Longitude 58.00000 W ( 58° 0.0' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 4.6 m
Maximum Sensor Depth 160.1 m
Minimum Sensor Height 5.7 m
Maximum Sensor Height 161.2 m
Sea Floor Depth 165.8 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.

Discrete inorganic nutrient samples from CTD bottles from RRS James Cook cruise 31 (JC031)

Originator's Protocol for Data Acquisition and Analysis

Discrete nutrient samples were collected from a variety of depths spanning the full depth of each CTD cast. Water was collected from depth using a stainless steel CTD frame fitted with a Sea-Bird SBE 32 twenty-four way carousel (s/n 32-45661-0621) equipped with 24, twenty litre OTE external spring water samplers. However, due to the complete loss of the CTD package at station 12, water was subsequently collected using a stainless steel CTD frame fitted with a Sea-Bird SBE 32 twenty-four way carousel (s/n 32-19817-0243) equipped with 20, ten litre OTE external spring water samplers (rosette positions 1-20) and 4, twenty litre OTE external spring water samplers (rosette positions 21-24). Nutrient concentrations (silicate, phosphate and nitrate) were analysed using a segmented-flow nutrient autoanalyser with colourimetric detection (Skalar SANplus SYSTEM analyser (type 4000) fitted with a Skalar autosampler (type 1000)). More detailed information on the sampling and analysis of nutrient samples can be found from pages 44-50 of the cruise report .

Limits of detection

The limits of detection and error between duplicate samples were determined by the originators. The limits of detection were defined as twice the level of background noise averaged out over the course of the cruise. The background noise levels in digital units (the arbitrary unit used by the Skalar autoanalyser software) were measured at the start and at the end of 10 of the 72 analyses. These were then averaged to give an averaged background noise level for the whole cruise. This number was then multiplied by 2. The concentration per digital unit was taken from the calculations used to determine the blank nutrient level in the artificial seawater matrix. Multiplying this number by the concentration per unit gives the limit of detection (Table 1).

Table 1. The limits of detection for the chemistries

Chemistry Limit of detection (µmol l -1 )
Nitrate + nitrite 0.15
Silicate 0.39
Phosphate 0.04

The errors for the nutrient analysis were worked out using a duplicate set of samples run during each analysis. A drift sample was included in each analysis to indicate if the baseline moves over the course of the run. These drift samples are included in pairs, i.e. 2 drift samples from the same batch are run one after the other. The first pair of these drifts was used as the duplicate samples in each of the 72 analyses. The error for the each analysis was determined using the equation below. These errors were then averaged over the cruise to obtain the error for the whole cruise (Table 2).

100 * (A - B) * C,   C = 2/(A + B)

Where A is the largest of the duplicates and B is the smallest.

Table 2. The errors associated with each of the chemistries

Chemistry Error in data (%)
Nitrate + nitrite 0.69
Silicate 0.36
Phosphate 0.45

BODC Data Processing Procedures

Data arrived at BODC in one Microsoft Excel format file which contained all the CTD casts sampled for nutrients during the cruise. The data received were loaded into the BODC database using established BODC data banking procedures. Absent data values were removed and data were screened in-house prior to loading. Data were loaded into BODC's database without any further changes.

Originator's parameters were mapped with BODC codes as follows:

Originator's variable Units Description BODC code Units Comments
Cruise - Cruise ID - - Converted to BODC ID
Type - Sampling platform - - Converted to BODC metadata
Station - CTD station - - Converted to BODC ID
Latitude decimal degrees Latitude North - -  
Longitude decimal degrees Longitude East - -  
Niskin number CTD niskin bottle position - -  
Pressure dbar Depth below sea surface - -  
Nitrate µmol l -1 Inorganic nitrate + nitrite from unfiltered samples NTRZAATX µmol l -1  
Flag number WOCE flag for nitrate + nitrite - - Converted to BODC quality control flag
Silicate µmol l -1 Inorganic silicate from unfiltered samples SLCAAATX µmol l -1  
Flag number WOCE flag for silicate - - Converted to BODC quality control flag
Phosphate µmol l -1 Inorganic phosphate from unfiltered samples PHOSAATX µmol l -1  
Flag number WOCE flag for phosphate - - Converted to BODC quality control flag

Data Quality Report

None (BODC assessment)

Problem Report

No problems to report (BODC assessment)


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 2009-02-26
End Date (yyyy-mm-dd) 2009-02-26
Organization Undertaking ActivityNational Oceanography Centre, Southampton
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierJC031_CTD_CTD_079
Platform Categorylowered unmanned submersible

BODC Sample Metadata Report for JC031_CTD_CTD_079

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
215440   10.00 1    161.10  162.10  160.10 Niskin bottle No problem reported    
215441   10.00 2    161.10  162.10  160.10 Niskin bottle No problem reported   Samples not drawn from this bottle
215442   10.00 4    110.90  111.90  110.40 Niskin bottle No problem reported    
215443   10.00 5    110.60  111.60  110.10 Niskin bottle No problem reported   Samples not drawn from this bottle
215444   10.00 8     76.20   77.20   76.00 Niskin bottle No problem reported    
215445   10.00 9     73.90   74.90   73.70 Niskin bottle No problem reported   Samples not drawn from this bottle
215446   10.00 12     50.10   51.10   50.10 Niskin bottle No problem reported    
215447   10.00 13     50.20   51.20   50.20 Niskin bottle No problem reported   Samples not drawn from this bottle
215448   10.00 16     24.70   25.70   25.00 Niskin bottle No problem reported    
215449   10.00 17     25.70   26.70   26.00 Niskin bottle No problem reported   Samples not drawn from this bottle
215450   10.00 20      4.50    5.50    5.00 Niskin bottle No problem reported    
215451   20.00 21      4.10    5.10    4.60 Niskin bottle No problem reported   Samples not drawn from this bottle
215452   20.00 22      4.10    5.10    4.60 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 JC031
Departure Date 2009-02-03
Arrival Date 2009-03-03
Principal Scientist(s)Elaine McDonagh (National Oceanography Centre, Southampton)
Ship RRS James Cook

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