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Lobe dynamics and transport predictions across the North-East Balearic front.
A. M. Mancho, E. Hernández-García, S. Wiggins, D. Small, V. Fernández
Inst. Matematicas y Fisica Fundamental. CSIC
a.m.mancho@imaff.cfmac.csic.es(Abstract received 04/22/2005 for session B)
ABSTRACT
Dynamical systems theory develops mathematical concepts that are applied to quantify transport processes in oceans. Hyperbolic fluid particle trajectories and their stable and unstable manifolds are the basic building blocks of the dynamical systems approach which describes Lagrangian transport. In a recent article [1] these tools are used to describe the turnstile mechanism in a quasigeostrophic double gyre model. In this work we extend those ideas to identify the same mechanism in a realistic turbulent flow that represents the dynamics of the surface layers of the Mediterranean Sea. A 3D primitive equation ocean model [2,3] provides us with daily surface velocity fields. Visual inspection of the resulting flow in the Mediterranean basin and of their instantaneous stagnation points, both elliptic and hyperbolic, reveals a meandering but persistent Eulerian current that flows eastwards above the Northern slope of the Balearic islands, bends slightly to the South after leaving Minorca island, and then crosses eastwards the Western Mediterranean. Its location seems to coincide with observed density fronts separating waters of Atlantic origin to the South and older Mediterranean waters to the North. Our purpose is to quantify transport across this current, which would greatly contribute to the mixing among the two water masses. Once a Lagrangian barrier is defined, the intersections between stable and unstable manifolds define lobes that evolve and transport fluid masses from the South to the North and from the North to the South. We compute lobe areas and with them we quantify North-South transport in that area of the Western Mediterranean.
[1] C. Coulliette, S. Wiggins. Nonlinear Process Geophys. 8, 69-94, 2001.
[2] D.E. Dietrich, R.L. Haney, V. Fernandez, S.A. Josey, J. Tintore. J. Mar. Syst. 52, 145-165, 2004.
[3] V. Fernandez, D.E. Dietrich, R.L. Haney, J. Tintore. Prog. Oceanogr. 2005.
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2005 LAPCOD Meeting, Lerici, Italy, June 13-17, 2005