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2002 LAPCOD Meeting
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LIDEX – Lagrangian Isopycnal Dispersion experiment
T. Rossby, D. Hebert
Graduate School of Oceanography, University of Rhode Island
trossby@gso.uri.edu(Abstract received 10/30/2002 for session A)
ABSTRACT
Mixing in the ocean has always been separated into two components: diapycnal and isopycnal. In the last few years significant progress has been made to determine the diapycnal mixing in the ocean interior, and the processes responsible for diapycnal exchange are known. However, the stirring and mixing of water along isopycnals is poorly understood and even the use of the terms stirring and mixing depends upon the horizontal scales that are being resolved, i.e. both process and measurement dependent.
We are preparing a field program to investigate the processes and dynamics of dispersion on isopycnal surfaces on scales from kilometers to hundreds of kilometers. Next Spring (2003) we plan to deploy clusters of isopycnal RAFOS floats on two density surfaces in the low-oxygen tongue off West Africa. The trajectories of the floats will allow absolute and relative dispersion rates to be determined. Higher-order statistics, such as strain and vorticity, can also be obtained from the clusters of floats.
The low-O2 waters off West Africa at ~10°N results originate in the area of strong upwelling and high biological activity at the coast. From hydrographic surveys it appears that the low-O2 water is advected westward from the upwelling sites, but little is known about the mean circulation in the area. The mean flow of the floats can answer this.
In this talk we review and discuss the float deployment strategy. The reason is that we know so little about the expected isopycnal relative dispersion. We are going to great lengths to put the floats on the same isopycnal so that vertical shear cannot corrupt the interpretation of the results. We plan to deploy the floats in clusters to study their dispersion. But how large should the clusters be, pairs, triplets, groups of ten? This is the question wed like to review.
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2002 LAPCOD Meeting, Key Largo, Florida, December 12-16, 2000