Dipole vortices in the Great Australian Bight
George R. Cresswell A D , Lars C. Lund-Hansen B and Morten Holtegaard Nielsen C
+ Author Affiliations
- Author Affiliations
A CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, Tas. 7001, Australia.
B Aquatic Biology, Bioscience, Aarhus University, Ole Worms Allé 1, 8000 Aarhus C, Denmark.
C Arctic Technology Centre, Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, DK-2800 Kgs. Lyngby, Denmark.
D Corresponding author. Email: george.cresswell@csiro.au
Marine and Freshwater Research 66(2) 135-144 https://doi.org/10.1071/MF13305
Submitted: 19 November 2013 Accepted: 3 May 2014 Published: 7 November 2014
Abstract
Shipboard measurements from late 2006 made by the Danish Galathea 3 Expedition and satellite sea surface temperature images revealed a chain of cool and warm ‘mushroom’ dipole vortices that mixed warm, salty, oxygen-poor waters on and near the continental shelf of the Great Australian Bight (GAB) with cooler, fresher, oxygen-rich waters offshore. The alternating ‘jets’ flowing into the mushrooms were directed mainly northwards and southwards and differed in temperature by only 1.5°C; however, the salinity difference was as much as 0.5, and therefore quite large. The GAB waters were slightly denser than the cooler offshore waters. The field of dipoles evolved and distorted, but appeared to drift westwards at 5 km day–1 over two weeks, and one new mushroom carried GAB water southwards at 7 km day–1. Other features encountered between Cape Leeuwin and Tasmania included the Leeuwin Current, the South Australian Current, the Flinders Current and the waters of Bass Strait.
Additional keywords: ADCP, Chl-a, CTD, NOAA, SeaWIFS.
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