Nonlinear Processes in Oceanic and Atmospheric Flows


Transport and mixing in oceanic surface flows

Author: Irina I. Rypina, Woods Hole Oceanographic Institution (WHOI), Physical Oceanography (PO) department.

Names and affiliation of other authors:
Lawrence J. Pratt, Woods Hole Oceanographic Institution (WHOI), PO department
Michael G. Brown, Univerisy of Miami, RSMAS
Ilya A. Udovydchenkov, Woods Hole Oceanographic Institution (WHOI), AOPE department
Huseyin Kocak, Unversity of Miami, Departments of Computer Science and Mathematics

Oral or poster: Oral presentation

Theoretical results (the Kolmogorov-Arnold-Moser theorem, and results relating to stable and unstable manifolds and lobe dynamics) and numerical methods (especially the computation of Finite-Time Lyapunov Exponents) from dynamical systems theory are used to study mixing and transport in oceanic flows, with an emphasis on surface flows in the Adriatic Sea and in the Philippines region. Much of the work focuses on the role of transport barriers in nonsteady two-dimensional and incompressible flows, their dynamics and methods of their identification. Motivated by observations of surface drifters in the Adriatic Sea, transport in
a three-gyre system is studied in some detail. Particular attention is paid to the issue of intergyre transport. The velocity field is assumed to be two-dimensional and incompressible, and composed of a steady three-gyre background flow on which a time-dependent perturbation is superimposed. Two systems of this type are considered: 1) an analytical model of the Adriatic Sea; and 2) an observationally-based altimetry-derived model of the Adriatic Sea. It is shown that for a small perturbation to the steady three-gyre background flow two of the gyres exchange no fluid with the third gyre. When the perturbation strength exceeds a certain threshold transport between all three gyres occurs. This behavior is described theoretically, illustrated using the analytic model and shown to be consistent with the observationally-based model of the Adriatic Sea.

*Satellite images from NASA and ESA

Nonlinear Processes in Oceanic and Atmospheric Flows. July 2-4, 2008. Castro Urdiales, Cantabria, Spain.