Nonlinear Processes in Oceanic and Atmospheric Flows

Presentation

Identification of Cusp Catastrophe in Gap Leaping Western Boundary Current Problem

Author: Joe Kuehl, University of Rhode Island, Graduate School of Oceanography.

Names and affiliation of other authors:
Vitalii A. Sheremet
University of Rhode Island, Graduate School of Oceanography

Oral or poster: Poster

Downloadable poster file:

Identification of Cusp Catastrophe in Gap Leaping Western Boundary Current Problem

(nloa2008KS.ppt, 1692160 bytes)

Abstract:
The Luzon Strait is an example of a western boundary current which negotiates a gap in bathymetry. In the gap region, the currents can exhibit multiple steady states (leaping the gap or penetrating the gap) and hysteresis (dependence on past flow state). Laboratory experiments on such flows are presented in order to investigate the system behavior in a two-dimensional parameter space of varying flow rate and rotation rate of the platform. The experiments were preformed in a cylindrical tank on a one-meter rotating table. A semi-circular ridge with a gap was inserted over sloping bottom topography in the active region, and the flow was driven by pumping water through sponges. The flow was visualized with the Particle Image Velocimetry method. By varying the flow rate (strength of current), we were able to identify transitions between leaping and penetrating flow states. These transitions bound a region of multiple steady states where hysteresis is present. The dynamics of the system is shown to exhibit a cusp catastrophe classified as A3. The scaling dependencies of some critical properties of the flow were analyzed. This catastrophe may explain irregularities encountered when analyzing observational data of gap leaping flows. Preliminary results of two layer experiments indicate similar dynamics.

*Satellite images from NASA and ESA

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