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Metadata Report for BODC Series Reference Number 776178

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

Data Description

Data Category

Hydrography time series at depth

Instrument Type

Name	Categories
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

Project(s)

RaTS

Data Identifiers

Originator's Identifier	CTD10823.DEP1
BODC Series Reference	776178

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm)	2005-01-25 15:00
End Time (yyyy-mm-dd hh:mm)	2006-01-25 00:00
Nominal Cycle Interval	3600.0 seconds

Spatial Co-ordinates

Latitude	67.56706 S ( 67° 34.0' S )
Longitude	68.23371 W ( 68° 14.0' W )
Positional Uncertainty	0.05 to 0.1 n.miles
Minimum Sensor Depth	253.0 m
Maximum Sensor Depth	253.0 m
Minimum Sensor Height	269.0 m
Maximum Sensor Height	269.0 m
Sea Floor Depth	522.0 m
Sensor Distribution	Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor Depth Datum	Unspecified -
Sea Floor Depth Datum	Unspecified -

Parameters

BODC CODE	Rank	Units	Short Title	Title
AADYAA01	1	Days	Date(Loch_Day)	Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01	1	Days	Time(Day_Fract)	Time (time between 00:00 UT and timestamp)
ACYCAA01	1	Dimensionless	Record_No	Sequence number
ADEPPS01	1	Metres	PrsSen	Depth below surface of the water body by semi-fixed in-situ pressure sensor and conversion to depth using unspecified algorithm
CNDCST01	1	Siemens per metre	CTDCond	Electrical conductivity of the water body by CTD
POTMCV01	1	Degrees Celsius	WC_Potemp	Potential temperature of the water body by computation using UNESCO 1983 algorithm
PREXPR01	1	Decibars	MeasPress_MW	Pressure (measured variable) exerted by the water body by semi-fixed in-situ pressure sensor and corrected to read zero at sea level
PSALST01	1	Dimensionless	P_sal_CTD	Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
SIGTEQST	1	Kilograms per cubic metre	Sigma-T	Sigma-T of the water body by computation from salinity and temperature using UNESCO algorithm
TEMPCC01	1	Degrees Celsius	Cal_CTD_Temp	Temperature 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)	2005-01-25
End Date (yyyy-mm-dd)	2006-02-15
Organization Undertaking Activity	British Antarctic Survey
Country of Organization	United Kingdom
Originator's Data Activity Identifier	RaTS_dep1
Platform Category	subsurface mooring

RaTS Mooring Deployment 1

The first deployment of the mooring at the RaTS site occurred on 25th January 2005 and was later recovered on 15th February 2006. Prior to deployment, all sensors were programmed to sample for a duration of a year. However, due to a delay in the recovery, all sensors except for the ADCP have a data gap of ~3 weeks. 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
1	67.56706 ^oS	68.23371 ^oW

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

Instrument	Depth (m)
Teledyne RDI's Workhorse Long Ranger 75kHz ADCP (5125)	200
RBR XR-420 CTD (10822)	200
Sediment trap (11262-09)	~212
RBR TR-1050 (11410)	~234
RBR XR-420 CTD (10823)	253
RBR TDR-2050 (11768)	268
RBR XR-420 CTD (10824)	283
Sediment trap (11262-01)	~391

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.

Other Series linked to this Data Activity - 775950 776210 777298 770644 776142

Cruise

Cruise Name	JR20050124 (JR112, JR113)
Departure Date	2005-01-24
Arrival Date	2005-01-25
Principal Scientist(s)	Mark Brandon (Open University Department of Earth and Environmental Sciences)
Ship	RRS James Clark Ross

Complete Cruise Metadata Report is available here

Fixed Station Information

Station Name	RaTS, Rothera
Category	Offshore area
Latitude	67° 34.40' S
Longitude	68° 13.50' W
Water depth below MSL	520.0 m

Fixed Station Document

The RaTS 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 a secondary 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 sites sampled:

Sample Site	Latitude	Longitude	Comments
CTD1	67.57330°S	68.22500°W	-
CTD2	67.58512°S	68.16483°W	-
WS3	67.56833°S	68.11869°W	Approx. position; sampling just off Biscoe Wharf

BODC image

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)

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

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