Metadata Report for BODC Series Reference Number 776234

• 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

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

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:

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

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

No Project Information held for the Series

Data Activity or Cruise Information

Data Activity

RaTS Mooring Deployment 3

The third deployment of the mooring at the RaTS site occurred on 17th December 2006 and was later recovered on 19th April 2007. Both deployment and recovery were carried out onboard the RRS James Clark Ross.

The exact position of the mooring is as follows:

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

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

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Rothera Oceanographic and Biological Time Series (RaTS) Fixed Station

The RaTS fixed station is made up of 3 CTD sampling sites and 2 mooring sites. The main CTD site is located in Marguerite Bay, ~4 km from shore and over a water depth of ~520 m. Marguerite Bay is enclosed by Adelaide Island to the north, Alexander Island to the south and the Antarctic Peninsula to the east (Figure 1 and 2). Waters are strongly influenced by the Antarctic Circumpolar Current. Surface waters during summer become warm through insolation and freshened by ice melt. In winter surface waters are generally colder and more saline and characterised by a thick mixed layer which persists into the summer months and is marked by a subsurface temperature minimum (for fuller details please see Meredith et al., 2004 and references therein). When optimal conditions aren't available the secondary CTD site is occupied. In times when fast ice prevented sampling at both the primary and secondary site, a third site is utilised close to the Rothera Research Station. However, only a water sample is collected during this time as the water is too shallow to allow for a cast to be conducted. The following provides details of the CTD sites sampled:

To compliment the CTD data collected at the RaTS station, fixed moorings were deployed between 2005 - 2007. The moorings consisted of a suite of sensors including ADCPs, CTDs and sediment traps.

Figures Location of Maguerite Bay, to the west of the Antarctic Peninsula (Meredith et al., 2004) and more specifically the location of the RaTS station (Wallace, 2007)

Reference

Meredith, M.P., I.A. Renfew, A. Clark, J.C. King, M.A. Brandon (2004) Impact of the 1997/98 ENSO on upper ocean characteristics in Marguerite Bay, western Antarctic Peninsula. Journal of Geophysical Research Letters, Vol. 109, C09013, doi:10.1029/2003JC001784

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

Related Fixed Station activities are detailed in Appendix 2

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:

Appendix 1: RaTS_dep3

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.

Appendix 2: RaTS, Rothera

Related series for this Fixed Station 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.