Hobart

Seminar abstract

Monday 20 November, 11.30 am (Tas time)
CSIRO Auditorium, Hobart

Klaus Getzlaff
Ocean Observing and Climate
National Oceanography Centre, UK

The circulation in the subtropical South Indian Ocean at 32S derived from Argo floats

Recent studies highlighted an increase in the gyre circulation across 32S in the subtropical South Indian Ocean of up to 40% from analysis of shipboard observations made in 1987, 1995 and 2002. This study uses CTD profiles from Argo floats between 2000 and 2005 to compute the circulation in the subtropical South Indian Ocean.

After applying a two step quality control to the profiles, an optimal interpolation scheme is used to map the float data onto the 2002 cruise track along 32S. Relative geostrophic transports are computed with a zero-velocity surface at 1950dbar. The time mean from the float data represents the structure of the subtropical gyre well and the estimated strength of the gyre is 63 +/- 18 Sv relative to and above 1950dbar. We have also computed a circulation scheme using reference velocities from the float's subsurface drift at 2000dbar, and compared it with an inverse solution based on 2002 cruise data. Although there is a difference in the overall gyre strength in both calculations, the float solution reproduces mesoscale features revealed by the inverse solution, like the deep fronts in the Lower Deep Water in the Crozet Basin (60E) and the Perth Basin (104E). The analysis of the annually sliced data using the reference velocities from float's subsurface drift suggest an increase in the gyre strength by 15% between 2002 and 2003. Whereas the seasonally sliced data suggest not only a change of 30% in the strength of the gyre but also a change in the overall structure.

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Piers Dunstan, (Biological seminars) CSIRO Marine and Atmospheric Research
(03) 6232 5382
Annabel Ozimec (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5462
Sandra Zicus, Antarctic Climate and Ecosystems CRC (03) 6226 7888
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 3/11/06