Metadata Report for BODC Series Reference Number 1650719

• 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

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

Instrument Description

The LADCP data were collected using the instrumentation detailed below:

Two Teledyne RDI Workhorse 300kHz ADCPs were mounted on the Sea-Bird 9 11 plus CTD frame at a time, one pointing downward (downlooker) and one upward (uplooker).

The first three stations were carried out with the standard instrument configurations supplied with the LDEO data acquisitions software 25 x 8 m bins, beam coordinates, zero blanking distance, narrow bandwidth, 2.5 m s^-1 ambiguity velocity, 1.5/2.0 s staggered ping rate.

There were large velocity warnings during processing therefore the ambiguity velocity was increased on station 4 to 3 m s^-1, on station 11 to 3.5 m s^-1 and on station 20 to 4.0 m s^-1.

In an attempt to increase sampling the pinging interval was decreased to 1.0/1.3 s on station 20. Inspection of the raw ensemble times indicated that the instruments were not capable of such a high pinging rate and the rate was therefore decreased to 1.2/1.4 s on station 23 and, finally, to 1.3/1.5 s on station 33.

Due to a problem with the star cable, station 41 was carried out with asynchronous pinging, with a staggered rate of 1.3/1.5 s in the master and 1.0 s in the slave.

There are no uplooker data for station 39 because of cable problems, and no valid uplooker data for station 54 due to hardware problems.

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

A total of 55 LADCP profiles were collected at all CTD stations in order to derive full-depth profiles of ocean velocity, as well as profiles of finestructure vertical shear.

Data processing

Preliminary shipboard processing of the LADCP data was carried out with the LDEO IX.6 LADCP processing software using one second averaged uncalibrated CTD data in order to correct the LADCP data for depth and sound speed. The CTD data were minimally processed using 'AlignCTD' which applies temporal shifts to align the sensor readings and 'CellTM' which corrects for the thermal mass. Velocity referencing was accomplished with post-processed (i.e. non-RDI) bottom-track data, 75kHz VMADCP data, and GPS information in the CTD time series files. The first bin of each instrument was discarded during processing. Note that the profiles 2, 23, 26, 35, 45, 47, 50, 52, 53 and 55 were not processed with bottom tracking and profile 7 did not have bottom tracking or VMADCP data.

Please refer to Thurnherr (2014) and cruise report for a more detailed processing methodology. However, please be aware that this processing guide is for software versions IX.7 to IX.10 only, and changes have been made between versions which have the potential for significantly changing the solutions.

References

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