Metadata Report for BODC Series Reference Number 1223115

• 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

No Problem Report Found in the Database

Quality Control Report

The originators identified a problem with the slow response of the conductivity sensor which caused salinity spikes in the data. This has been rectified by the originator as described in the originator's data processing section.

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

WET Labs WETStar Fluorometers

WET Labs WETStar fluorometers are miniature flow-through fluorometers, designed to measure relative concentrations of chlorophyll, CDOM, uranine, rhodamineWT dye, or phycoerythrin pigment in a sample of water. The sample is pumped through a quartz tube, and excited by a light source tuned to the fluorescence characteristics of the object substance. A photodiode detector measures the portion of the excitation energy that is emitted as fluorescence.

Specifications

By model:

All models:

Further details can be found in the manufacturer's specification sheet, and in the instrument manual.

Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)

The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.

There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.

Specifications

POS MV 320

POS MV WaveMaster

POS MV Elite

¹ One Sigma, depending on quality of differential corrections
² Whichever is greater, for periods of 20 seconds or less

Further details can be found in the manufacturer's specification sheet.

WETLabs C-Star transmissometer

This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.

Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.

This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.

Specifications

Further details are available in the manufacturer's specification sheet or user guide.

DIMES James Cook Cruise JC069 Surface Hydrographic Instrumentation

The following table shows the surface hydrography sensors used on board the ship, located in the ship's laboratory and non toxic flow, between 5 and 6 m deep.

SeaBird MicroTSG Thermosalinograph SBE 45

The SBE45 MicroTSG is an externally powered instrument designed for shipboard measurement of temperature and conductivity of pumped near-surface water samples. The instrument can also compute salinity and sound velocity internally.

The MicroTSG comprises a platinum-electrode glass conductivity cell and a stable, pressure-protected thermistor temperature sensor. It also contains an RS-232 port for appending the output of a remote temperature sensor, allowing for direct measurement of sea surface temperature.

The instrument can operate in Polled, Autonomous and Serial Line Sync sampling modes:

• Polled sampling: the instrument takes one sample on command
• Autonomous sampling: the instrument samples at preprogrammed intervals and does not enter quiescence (sleep) state between samples
• Serial Line Sync: a pulse on the serial line causes the instrument to wake up, sample and re-enter quiescent state automatically

Specifications

Further details can be found in the manufacturer's specification sheet.

Data Processing Procedures

Originator's Data Processing

Data were logged daily by the onboard logging system (TECHSAS). TSG data were transferred from the TECHSAS system and reformatted into Mstar format NetCDF using NOC-generated Mstar processing scripts on a daily basis. TSG data were then cleaned by setting all data values to null when the housing temperature rose while the sea temperature remained steady, attributed to interruptions in the pumping and including periods when the ship was in port.

It was noted part way through the cruise that there were significant salinity spikes each time there was a strong change in temperature. The characteristic was a negative spike in salinity when temperature was warming, which is characteristic of the conductivity responding slowly. When this was noticed, an attempt was made to estimate a time constant to lag the temperature and remove salinity spikes but was unsuccessful, therefore, spikes were removed by hand instead. The problem became worse during the cruise and so a more determined effort was made to estimate a lagged temperature and fix the salinity. It was decided that a systematic search was required to characterise the history of the problem during the cruise. A lagged temperature was constructed using a one-sided filter. A function was created so that for each time step, lagged temperature is the mean of all temperatures within the last tlag seconds. Thus a tlag of 120 corresponds to a lag time of about 60 seconds, the salinity was then calculated from lagged temperature. Further, a smoothed salinity was calculated at each test time as a mean of the salinities within 500 seconds either side of that test time. The residual was the standard deviation of the lagged salinity about the smoothed salinity. Thus, a small residual is presumed to mean success at removing salinity anomalies on a timescale of minutes, as required. A script was used to search each day of data and each possible value of tlag in the range 0:10:150 seconds.

TSG data up to day 13 March 2012 was as follows:
1) Early in the cruise, the optimum residual for this process was small or at zero tlag.
2) Approximately 28 February 2012, the optimum value of tlag was near 60.
3) From day 01 March 2012, the optimum value of tlag was near 120.

Accordingly, it was decided that salinity would be re-calculated from the start of the cruise using tlag = 0 for days up to and including 28 February 2012, and tlag = 120 for days equal to and greater than 01 March 2012. The script created 1-minute median bin averaged data, then removed known bad data including times when the TSG pump was off. The full processing sequence can be found in the cruise report.

All TSG data values were removed at times when the pump was off or the data were considered bad, except for conductivity. Times when the pump was off are as follows:
The start of the pumped data began 02 February 2012 13:00 hours
First Stanley call, the pump was off between 18 February 2012 08:00 and 16:00 hours
Second Stanley call, the pump was off between 21 February 2012 12:00 hours and 24 February 2012 12:00 hours
End of logging from 17 March 2012 18:06 hours to the end of cruise

The following file was submitted to BODC:

Calibration

Salinity data were calibrated against bottle salinity data. 182 bottle samples were analysed for TSG calibration, collected every four hours excluding time when the ship was on station or due to weather conditions. A script was used to merge the clean 1-minute TSG data onto bottle samples. Individual bottle residuals were plotted, as well as a smoothed (41-point boxcar filter) plot of the residuals, which was then used as a slowly-varying adjustment to the TSG salinity.

BODC Data Processing

The Mstar file was used to provide all of the sea surface hydrography data and were reformatted to the internal QXF format via the nearest neighbour method. All reformatted and calibrated data were visualised using the in-house Edserplo software. Suspect data were marked by adding the appropriate quality control flag. On occasions where all other TSG data had been removed the conductivity data were flagged as improbable. Data were provided when the ship was still in port, therefore, the file was trimmed at the beginning to match the cruise start date.

The following table shows how the variables within the files were mapped to appropriate BODC parameter codes:

TSG Mstar file

Calibration

The manufacturer's calibration was applied to the raw fluorometer output to calibrate the raw volts to concentration of chlorophyll-a per (milligrams per cubic metre) using the Wetlabs WET-Star fluorometer calibration sheet.

The following equation was used: CPHLUMTF = 13.1 * (output volts - 0.079).

The transmissometer was calibrated using the manufacturer's calibration from volts to light transmission (%) and beam attenuation (per metre). The equation below, taken from the Wet Labs CST calibration sheet was used. No field measurements were available to be used for the calibration.

POPTDR01 = 100 * (Vsig - Vdark) / (Vref - Vdark) where: Vdark= 0.059 and Vref= 4.679.
ATTNDR01 = 1/0.25 * ln(POPTDR01).

Project Information

Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) project document

DIMES is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.

The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing.

DIMES includes tracer release, isopycnal following RAFOS floats, microstructure measurements, shearmeter floats, EM-APEX floats, a mooring array in Drake Passage, hydrographic observations, inverse modeling, and analysis of altimetry and numerical model output.

DIMES is sponsored by the National Science Foundation (U.S.), Natural Environment Research Council (U.K) and British Antarctic Survey (U.K.)

For more information please see the official project website at DIMES

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

World Ocean Circulation Experiment (WOCE) Southern Repeat Section 1 - South America to West Antarctic Peninsula

WOCE established a repeat hydrographic section across Drake Passage and designated it SR1 (also known as A21). The section is located between the Southern tip of South America and the West Antarctic Peninsula within a bounding box of 55° 19.40' S, 68° 15.80' W (North-Western corner) and 64° 8.52' S, 63° 4.80' W (South-Eastern corner).

A table of cruises which occupied SR1 is presented below with links to the relevant cruise reports (where available).

Related Fixed Station activities are detailed in Appendix 1

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: Drake Passage - WOCE SR1

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.