Metadata Report for BODC Series Reference Number 776222


Metadata Summary

Data Description

Data Category Hydrography time series at depth
Instrument Type
NameCategories
RBR XR-420 CTD Marine  water temperature sensor; salinity sensor
Instrument Mounting subsurface mooring
Originating Country United Kingdom
Originator Prof Andy Clarke
Originating Organization British Antarctic Survey
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) RaTS
 

Data Identifiers

Originator's Identifier CTD10824.DEP2
BODC Series Reference 776222
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2006-02-17 13:59
End Time (yyyy-mm-dd hh:mm) 2006-12-16 21:59
Nominal Cycle Interval 3600.0 seconds
 

Spatial Co-ordinates

Latitude 67.56623 S ( 67° 34.0' S )
Longitude 68.23437 W ( 68° 14.1' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 274.0 m
Maximum Sensor or Sampling Depth 274.0 m
Minimum Sensor or Sampling Height 248.0 m
Maximum Sensor or Sampling Height 248.0 m
Sea Floor Depth 522.0 m
Sea Floor Depth Source CRREP
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor or Sampling Depth Datum Unspecified -
Sea Floor Depth Datum Unspecified -
 

Parameters

BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ACYCAA011DimensionlessSequence number
ADEPPS011MetresDepth below surface of the water body by semi-fixed in-situ pressure sensor and conversion to depth using unspecified algorithm
CNDCST011Siemens per metreElectrical conductivity of the water body by CTD
POTMCV011Degrees CelsiusPotential temperature of the water body by computation using UNESCO 1983 algorithm
PREXPR011DecibarsPressure (measured variable) exerted by the water body by semi-fixed in-situ pressure sensor and corrected to read zero at sea level
PSALST011DimensionlessPractical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
SIGTEQST1Kilograms per cubic metreSigma-T of the water body by computation from salinity and temperature using UNESCO algorithm
TEMPCC011Degrees CelsiusTemperature of the water body by CTD and verification against independent measurements

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

The conductivity channel (CNDCST01) shows sign of drifting thoughout the deployment (decreasing with time). Step changes are also observed on the conductivity channel and it is believed that both of these problems are thought to derive from biofouling of the conductivity sensor. Since the channels density (SIGTEQST) and salinity (PSALST01) are derived using the conductivity data, the drift and step changes are also apparent here.


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

RBR XR-420 CTD

The XR-420 CTD Marine is a small, autonomous conductivity, temperature and depth recorder, from which high accuracy speed of sound and salinity can be derived. Its titanium housing provides a depth rating for the cell of 6,600m which can be axial to the logger, whilst also providing shielding and stable cell geometry. The normal marine conductivity range of 0 to 70 mS/cm is measured by an inductive cell to an accuracy of ±0.003 mS/cm and with a response time of less than 95 milliseconds when profiling. It uses a three-coil system with a closed loop feedback for superior temperature compensation. 8MB of nonvolatile flash memory allows for 2, 400, 000 readings which can be logged on one set of high-powered 3V lithium batteries

Specifications

  Temperature (°C) Conductivity (S/m) Optional Pressure
Measurement Range -5 to +35 0 to 7 (0 to 70 mS/cm) 0 to full scale range: 10/25/60/150/250/740/1000/2000/ 3000/4000/6600 metres (dBar)
Accuracy ± 0.002 °C ± 0.003 mS/cm ± 0.05% full scale
Resolution <0.00005 °C <0.0001 mS/cm <0.001% full scale
Communications RS-232/485; logged, cable, or telemetry
Download Speed ~115,000 samples/minute
Memory 8Mbyte nonvolatile flash (2,400,000 samples)
Sample Rate 1Hz* to 24 hours (programmable)
Clock Accuracy ± 32 seconds/year
Power QTY 4, 3V CR123A cells.
Housing Depth rating of the cell of up to 6,600m
Size 400mm x 64mm
Weight of plastic (without pressure) In water: 0.389Kg
In air: 1.259Kg
Calibration NIST traceable standards

Further information can be found on the Official RBR Website or in the manufacturer's specification sheet.

BODC Processing

The data arrived at BODC in Matlab binary .MAT files representing CTD data from a mooring positioned in Marguerite Bay, Antarctica which was deployed in conjuction with the Rothera Oceanographic and Biological Time Series (RaTS). These were reformatted to the internal QXF format using BODC transfer function 390. The following table shows how the variables within the Matlab files were mapped to appropriate BODC parameter codes:

Originator's Variable Units Description BODC Parameter Code Units Comment
press decibars Pressure exerted by water column measured by semi-fixed in-site pressure sensor and corrected to read zero at sea-level PREXPR01 decibars External offset applied
depth metres Depth below surface of the water column by semi-fixed in-situ pressure sensor and conversion to depth using unspecified algorithm ADEPPS01 metres calculated from corrected pressure and latitude
tempcal degrees Celsius Temperature of the water column by CTD and verification against independent measurements TEMPCC01 degrees Celsius -
condcal milliSiemens per centimeter Electrical conductivity of the water column by CTD CNDCST01 Siemens per metre Raw data divided by 10 during transfer to convert to BODC parameter units
salcal dimensionless Practical salinity of the water column by CTD and computation using UNESCO 1983 algorithm PSALST01 dimensionless calculated using calibrated temperature and conductivity
sig0cal kilograms per metre cubed Sigma-T of the water column by computation from salinity and temperature using UNESCO algorithm SIGTEQST dimesionless calculated using calibrated temperature and conductivity

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag.

External Data Processing

The RaTS moored CTD data were subjected to a number of checks and calibrations externally, prior to be being received by BODC.

Pressure data were calibrated against deck pressure data from the CTD plus depth data derived from ADCP (on the same mooring) deck pressures. See table 1 for further details.

The conductivity and temperature data were calibrated against CTD data collected from the CTD profiles made at the RaTS site. Only small offsets were applied to the temperature data (see table 1) whilst the moored conductivity data were significantly different from the RaTS profile data. The mean conductivity value over the moored time series was corrected to the mean value from the RaTS dataset over the same period to give a corrected conductivity time series.

Table 1: Offsets applied to the moored CTD data at RaTS

Moored sensor Deployment Press. offset (dbar) Cond. offset (mS/cm) Temp. offset (oC)
CTD10822 1 9.76 0.2100 0.0486
2 9.71 -0.0398 -0.0709
3 9.75 0.2474 0.0356
CTD10823 1 9.64 0.0727 0.0160
2 9.54 -0.0108 -0.0407
3 9.71 -0.1550 0.0063
CTD10824 1 9.76 0.2477 0.0101
2 9.61 0.03044 -0.0307
3 9.71 0.3159 0.0027

Reference:

Wallace, M.I., 2007. Ocean circulation, properties and variability in Marguerite Bay, west Antarctic Peninsula. PhD Thesis. The Open University, Milton Keynes, UK.


Project Information

Rothera Oceanographic and Biological Time Series (RaTS)

The RaTS programme, which has been run by the British Antarctic Survey since 1997, involves the long-term monitoring of the nearshore marine environment. The project has always been funded by the Natural Environment Research Council (NERC); it initially was a discrete project within the BAS marine biological programme but has now been moved to form a component of the BAS Long Term Monitoring and Survey (LTMS) programme.

Scientific Aims

The RaTS programme was started with two broad aims. The first was to provide a suite of oceanographic data that would provide the environmental background to aid interpretation of the nearshore marine ecology. The second was to test a series of broad hypotheses concerned with surface and deep water coupling and environmental forcing of the nearshore oceanic environment. The key questions formulated at the start of the programme were:

1. To what extent is the physics of the upper water column (ice dynamics, thermal characteristics and vertical structure) related to large-scale forcing such as the El-Niño Southern Oscillation?

2. How and to what extent is variability in the physics of the upper water column transferred to biological processes, particularly primary production?

3. How and to what extent does variability in the timing and in the intensity of the summer phytoplankton bloom affect key ecological processes in the benthos, and particularly feeding, growth and reproduction?

To answer these questions an integrated programme of regular oceanographic and biological measurements was implemented. Observations are taken at a fixed station, selected to be safely accessible by boat in summer and snowmobile in winter whilst being well away from normal ship traffic. Operations at this site included regular CTD casts, discrete water sampling and the deployment of three moorings equipped with current profilers and other hydrography sensors.


Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 2006-02-17
End Date (yyyy-mm-dd) 2006-12-16
Organization Undertaking ActivityBritish Antarctic Survey
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierRaTS_dep2
Platform Categorysubsurface mooring

RaTS Mooring Deployment 2

The second deployment of the mooring at the RaTS site occurred on 17th February 2006 and was later recovered on 16th December 2006. Both deployment and recovery were carried out onboard the RRS James Clark Ross.

The exact position of the mooring is as follows:

Deployment Latitude Longitude
2 67.56623 oS 68.23437 oW

Details of the instrumentation associated with the first deployment of the mooring at the RaTS site:

BODC image
Instrument Depth (m)
Teledyne RDI's Workhorse Long Ranger 75kHz ADCP (5125) 196
RBR XR-420 CTD (10822) 196
Sediment trap (11262-09) ~208
RBR TR-1050 (11410) ~228
RBR XR-420 CTD (10823) 244
RBR TDR-2050 (11768) 259
RBR XR-420 CTD (10824) 274
Sediment trap (11262-01) ~382

Figure of mooring and table of instruments with corresponding depths (Wallace, 2007)

Reference

Wallace, M.I., 2007. Ocean circulation, properties and variability in Marguerite Bay, west Antarctic Peninsula. PhD Thesis. The Open University, Milton Keynes, UK.

Related Data Activity activities are detailed in Appendix 1

Cruise

No Cruise Information Available for this Series

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
Q value below limit of quantification

Appendix 1: RaTS_dep2

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.

Series IdentifierData CategoryStart date/timeStart positionCruise
770656Currents -subsurface Eulerian2006-02-17 11:36:0667.56623 S, 68.23437 WRRS James Clark Ross JR20060216 (JR136, JR137)
775962Hydrography time series at depth2006-02-17 13:59:5767.56623 S, 68.23437 WRRS James Clark Ross JR20060216 (JR136, JR137)
776154Hydrography time series at depth2006-02-17 13:59:5767.56623 S, 68.23437 WRRS James Clark Ross JR20060216 (JR136, JR137)
776191Hydrography time series at depth2006-02-17 13:59:5767.56623 S, 68.23437 WRRS James Clark Ross JR20060216 (JR136, JR137)
777305Hydrography time series at depth2006-02-17 13:59:5767.56623 S, 68.23437 WRRS James Clark Ross JR20060216 (JR136, JR137)