CTD bottle samples of nutrients, TDN and DOC collected on cruise D253 along Extended Ellett Line
Originator's Protocol for Data Acquisition and Analysis
A large scale CTD survey of the Iceland Basin and Rockall Trough was carried out during this cruise along the Extended Ellett Line, comprising a total of 153 CTD casts.
To determine nutrients, samples were drawn from all depths at all stations, with the exception of stations 14024, 14025 and 14026, directly into virgin polystyrene coulter counter vials. Samples were then stored in a fridge before analysis, which was generally commenced within 12 hours. The concentrations of nitrate + nitrite, phosphate and silicate were then determined using conventional colorimetric methods using a Skalar San Plus autoanalyser. Further details are in Allen (2001), pages 146 to 153.
TDN (Total Dissolved Nitrogen) and DOC (Dissolved Organic Carbon) were determined by high temperature oxidation- further details on pages 170 to 171 of Allen (2001).
References Cited
Allen, J. T. 2001. RRS Discovery cruise 253 04 May - 20 Jun 2001 . Faeroes, Iceland, Scotland Hydrographic and Environemental Survey (FISHES). Southampton Oceanography Centre Cruise Report, No 37, 206pp.
Instrumentation Description
The samples were taken with a CTD frame with 24 position rosette and 24 Niskin bottles. Nutrients were analysed with a Skalar San Plus autoanalyser.
BODC Data Processing Procedures
Data were received at BODC in the form of pstar format sample files, and various spreadsheets containing nutrient, chl-a, TDN and DOC measurements. Bottle metadata were derived from the pstar files as these recorded rosette position and pressure, whereas some spreadsheets only recorded the nominal depths of bottle firing. Having combined the two data sources, the data were loaded into the BODC database using established BODC data banking procedures.
Where no pressure or depth information could be found from any source, a small number of bottles and measurements from them were discarded.
Parameters from the originator's source files were mapped to BODC parameter codes as follows:
| Originator's Parameter | Unit | Description | BODC Parameter Code | BODC Unit | Comments |
|---|---|---|---|---|---|
| no2+3 | µmol/l | Nitrate and nitrate from bottle sample determined by Auto Analyzer | NTRZAATX | Micromoles per litre | n/a |
| sio3 | µmol/l | Silicate from bottle sample determined by Auto Analyzer | SLCAAATX | Micromoles per litre | n/a |
| po4 | µmol/l | Phosphate from bottle sample determined by Auto Analyzer | PHOSAATX | Micromoles per litre | n/a |
| TDN Total Dissolved Nitrogen | mM | TDN from bottle sample determined by high temperature oxidation | NTOTCOD1 | Micromoles per litre | n/a |
| DOC Disslved Organic carbon | mM | DOC from bottle sample determined by high temperature oxidation | CORGCOF1 | Micromoles per litre | n/a |
Data Quality Report
No report provided by the originator, but information about data quality is included in Allen (2001).
Problem Report
No problem report.
| bindepth | m | Depth of ADCP bin | DBINAA01 | m | - |
| evelcal | cm s -1 | Relative Eastward current velocity | LCEWAS01 | cm s -1 | Not in final file as absolute velocities are present |
| nvelcal | cm s -1 | Relative Northward current velocity | LCNSAS01 | cm s -1 | Not in final file as absolute velocities are present |
| velvert | cm s -1 | Vertical current velocity | LRZAAS01 | cm s -1 | - |
| velerr | cm s -1 | Velocity error | LERRAS01 | cm s -1 | - |
| intense1 | db | Beam 1 intensity | ASAMSP00 | db | - |
| intense2 | db | Beam 2 intensity | ASAMSP02 | db | - |
| intense3 | db | Beam 3 intensity | ASAMSP03 | db | - |
| intense4 | db | Beam 4 intensity | ASAMSP04 | db | - |
| ve | cm s -1 | Ship's Eastward velocity | APEWGP01 | cm s -1 | - |
| vn | cm s -1 | Ship's Northward velocity | APNSGP01 | cm s -1 | - |
| absve | cm s -1 | Absolute Eastward current velocity | LCEWAS01 | cm s -1 | - |
| absvn | cm s -1 | Absolute Northward current velocity | LCNSAS01 | cm s -1 | - |
| lat | Degrees | Latitude | ALATGP01 | Degrees | - |
| lon | Degrees | Longitude | ALONGP01 | Degrees | - |
| distrun | km | Distance run | DSRNCV01 | km | - |
Reformatted data were visually checked using the in-house editor EDSERPLO. No data values were edited or deleted. Flagging was achieved by modification of the associated quality control flag to 'M' for suspect values and 'N' for nulls.
Once quality control screening was complete, the data were archived in the BODC National Oceanographic Database and the associated metadata were loaded into an ORACLE Relational Database Management System.
