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Deep, cross-equatorial eddies

 

作者: Sergey Borisov,   Doron Nof,  

 

期刊: Geophysical & Astrophysical Fluid Dynamics  (Taylor Available online 1998)
卷期: Volume 87, issue 3-4  

页码: 273-310

 

ISSN:0309-1929

 

年代: 1998

 

DOI:10.1080/03091929808221150

 

出版商: Taylor & Francis Group

 

关键词: Particle trajectories;inter-hemispheric exchange;potential vorticity alteration;eddy splitting

 

数据来源: Taylor

 

摘要:

The question of how deep ocean eddies can cross the equator is addressed with the aid of analytical and numerical models. We focus on the possibility that deep ocean (lens-like) eddies can cross the equator via deep cross equatorial channels on the ocean floor. We first examine the behavior of solid balls (i.e., free particles) in a meridional parabolic channel on a β plane. Such balls are subject to similar topographical forcing and inertial forces that a lens is subject to, except that pressure forces and friction are absent. We examine both single isolated balls and a “cloud” of (noninteractive) balls. In general, the balls' trajectories have a chaotic character; a fraction of the cloud crosses the equator and ends up in the northern hemisphere, and a fraction is left behind. More realistic numerical experiments (with a fully nonlinear reduced-gravity isopycnic model of the Bleck and Boudra type) show similar behavior. In all cases the equator acts as an “eddy smasher” in the sense that it breaks the lens into at least two parts, one crosses the equator and ends up in the northern hemisphere, and the other is left behind. Here, however, the system is not chaotic. Despite the obvious differences between clouds of balls and eddies, there is a remarkable similarity between the percentage of balls that penetrate into the opposite hemisphere and the percentage of eddies' mass that ends up in the other hemisphere. This suggests that the geometry of the channel and the presence of the equator determine how the fluid will be partitioned among the two hemispheres.

 

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