New Zealand Journal of Marine and Freshwater Research abstracts

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Analysis of quasi-synoptic eddy observations in the New Zealand subantarctic

Michael J. M. Williams

National Institute of Water and Atmospheric
 Research Limited
Private Bag 14 901
Wellington, New Zealand
email: m.williams@niwa.co.nz

Abstract  In June 2001 a warm core eddy was observed simultaneously by satellite and shipboard measurements to the south of the Subtropical Front, at c. 50°S 172°W. The simultaneous acquisition of satellite altimeter data, together with shipboard velocity, and temperature and salinity observations has allowed a 3-dimensional picture of this eddy to be developed. Analysis of the water mass composition showed it consisted of a mixture of between 45% and 70% Subtropical Water; the remainder being Subantarctic Water. The centre of the eddy was 1000 m deep. To find the radius of the eddy a rankine vortex was fitted to the Acoustic Doppler Current Profiler velocity field, this gave a best fit of 65 km with a range from 30 to 80 km. For an eddy of this size the available potential energy was estimated at 2.4 x 10¹³ J and the eddy’s kinetic energy at 6.9 x 10¹⁴ J.

Keywords  eddy; subantarctic; Acoustic Doppler Current Profiler; rankine vortex

M03006; Online publication date 15 March 2004; Received 3 February 2003; accepted 24 December 2003
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38: 183-194
0028-8330/04/3801-0183 © The Royal Society of New Zealand 2004

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