Oceanic three-dimensional Lagrangian Coherent Structures: A study in the Benguela upwelling region.

摘要

We study three dimensional oceanic Lagrangian Coherent Structures (LCSs) in the Benguela region, as obtained from an output\udfrom the ROMS model. To this end we first compute Finite-Size Lyapunov exponent (FSLE) fields in the region volume, characterizing mesoscale stirring and mixing there. Average FSLE values show a general decreasing trend with depth, but there is a local\udmaximum at about 100m depth. LCSs are extracted as ridges of the calculated FSLE fields. They present a “curtain-like” geometry\udin which the strongest attracting and repelling structures appear as quasivertical surfaces. LCSs around a particular cyclonic eddy,\udpinched o from the upwelling front are also calculated. The LCSs are confirmed to provide pathways and barriers to transport in\udand out of the eddy