SCM9 (SWINDEX)

SWINDEX (the Southwest Indian Ocean Experiment) produced 20 current meter records and 2 thermistor chain records from 5 moorings. You can view metadata and/or download the records by clicking on links in the tables below. Each current meter or thremistor chain record is identified in the tables by its depth and the name of the mooring. A brief description of the experiment also is available. You may want to look at a map of the array to see where the moorings were. If you download any of the current meter records you should review the note on file format. From here you can also move up one level to the list of WOCE experiments.

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The Southwest Indian Ocean Experiment entailed hydrographic surveys and an array of current meters. The hydrographic studies were undertaken on DISCOVERY cruises 201 and 213, with the goal of ascertaining whether any part of the Antarctic Circumpolar Current passes north of or across the Crozet Plateau. An array of current meter moorings (which also carried two thermistor chains) was deployed on and near the crest of the Plateau (see map).

Seven moorings designated A through G were installed in April 1993. Five moorings were recovered 22 months later. All of the instruments, including the thermistor chains, were manufactured by Aanderaa. RCM5 current meters were used at shallower depths, and RCM7s and RCM8s at the deeper levels.

Processing notes: (1) RCM5s record a speed value obtained by averaging over the sampling interval, but measure direction instantaneously at the end of the interval. In order to mitigate the mismatch between speed and direction (severe because of the long sampling interval), each speed was paired with a direction obtained by averaging the direction recorded at the end of the interval, with the previous recorded direction. This type of correction was not required for the RCM7s and RCM8s, which are vector-averaging instruments. (2) When the speed rotor stalled the speed was set equal to the stall speed, which was as low as 1.1 cm/sec for some of the current meters and as high as 2.2 cm/sec for others.

The hydrographic data referred to above can be found at the WOCE Hydrographic Program Office (WHPO) with expocodes 74DI201_1 and 74DI213_1, the 4th and 7th occupations of area ISS1.

Related publications

Pollard, R.T., J.F. Read et al (1994): RRS Discovery Cruise 201, 23 Mar - 3 May 1993. South West Indian Ocean Experiment (SWINDEX). IOSDL Cruise Report 240, 96pp.

Pollard, R.T., J.F. Read et al (1995): RRS Discovery Cruise 213, 6 Jan - 21 Feb 1995. South West Indian Ocean Experiment (SWINDEX). IOSDL Cruise Report 247, 104pp.

Pollard, R. and J. Read (1996): Current measurements in SWINDEX. In Understanding ocean circulation: UK WOCE: the first six years (ed. R. Pollard and D. Smythe-Wright). Southampton: Southampton Oceanography Centre. 32pp.

Pollard, R. and J. Read (1997): Two-year long current time series from the southwest Indian Ocean. International WOCE Newsletter, 29, 3-7.

Read, J.F. and R. T. Pollard (1999): Deep inflow into the Mozambique Basin. J. Geophys. Res. 104 (C2), 3075-3090.

Pollard, R.T. and J.F. Read (2001): Circulation pathways and transports of the Southern Ocean in the vicinity of the Southwest Indian Ridge. J. Geophys. Res., 106(C2), 2881-2898.

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netCDF is a self-documenting format that can be accessed by a variety of software tools. We have included here a Matlab script that can be used to read netCDF current records in an environment that contains the Matlab/netCDF interface created by CSIRO. You can Click here to learn more about netCDF.

We are aware that users who are unfamiliar with netCDF or who lack software to deal with it, may find the netCDF format more a deterrent than an aid to effective use of the data. We have included in this CDROM set a second disk that is identical to this one, except that the current meter records have OSU's "Stranger" format. The Stranger format, like netCDF, is self-documenting but utilizes the ASCII code. It is easily readable by both humans and computers; you may find it preferable to netCDF.

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