Metadata Report for BODC Series Reference Number 1737442

• 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

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

Instrument Description

The LADCP data were collected using the instrumentation detailed below:

The instrument orientation on the rosette was changed several times during the cruise in order to try to minimise wake effects. Three different configurations were used:
Original orientation. Stations 1-18 and 26-34.
Uplooker rotated. Stations 19-25.
Up and Downlooker rotated. Stations 36-128.

After the first test cast, it was found that the uplooker (15060) had a broken beam. It was then replaced with another unit (14897). This unit worked well from station 2 to station 86, but then started to show a weak 2nd beam. It was replaced with another unit (13400) on station 90. However, the unit started to show a weak 3rd beam on station 115, by station 116 the 3rd beam had broken and at station 117 the 2nd beam had broken. It was replaced with another unit (12736) on station 118.

Teledyne RDI's Workhorse Monitor ADCP

The Workhorse Monitor acoustic doppler current profler (Teledyne RD Instruments) is a long-range and long-term self contained ADCP. It has a patented four beam signal (300, 600 or 1200 kHz) and a standard depth rating of 200m or 600m. It operates effectively between temperatures of -5°C and 45°C and has a velocity accuracy of ±1% ±5mm/s.

BODC Processing

LDEO processed data were provided by the originator in Matlab and ASCII formats. The LDEO processed data in ASCII format were converted into BODC internal format after discussion with the originator. All data provided were from the downward looking RDI 300 kHz Workhorse ADCP which was in operation at the time. The following table shows how the variables within the ASCII files were mapped to appropriate BODC parameter codes:

All reformatted data were visualised using the in-house Edserplo software. Suspect and missing data were marked by adding an appropriate quality control flag.

Note that the more complex LDEO processed data are available on request in Matlab format as well as the unprocessed raw LADCP files.

Originator's Data Processing

Sampling Strategy

LADCP profiles were attempted at all CTD stations in order to derive full-depth profiles of ocean velocity, as well as profiles of finescale vertical shear of horizontal velocities. In total 110 LADCP profiles were obtained successfully.

Data processing

On the ship, the LADCP data were processed using the inverse method maintained by Andreas Thurnherr using LEDO software version IX 9.

One second CTD time-series data, with merged GPS, were used to improve the accuracy of the depth estimation from LADCP data. In addition, VMADCP data collected with a 75kHz system provided profiles of zonal and meridional velocities as well as their standard deviations.

Post cruise, all profiles were re-processed following the same method as on the ship, which is detailed in thecruise report. The main difference between the processing was that the RDI bottom-track data was used after the cruise, whereas the on-ship processing used post-processed bottom track data. For profile 117 the upward-looking data were also removed during post-cruise processing. For final processing, no wake editing was done and the VMADCP data were used to constrain the velocities.

Please refer to Thurnherr (2014) and post-cruise QC document for more details about the processing methodology.

References

Thurnherr, A. M., 2014. How To Process LADCP Data With the LDEO Software, Versions IX.7 to IX.10.

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

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: