Powell, T. A. University of California, zackp@socrates.berkeley.edu

THE EFFECT OF REALISTIC OCEAN MIXING ON NPZ OSCILLATIONS

The dynamics of spatially extended, diffusively coupled predator-prey models have long been known to exhibit chaotic dynamics (e.g., Pascual, 1993) but such effects within even simple NPZ models have not been demonstrated. We investigate the possibility of such complex nonlinear dynamics using the Franks and Walstad (1997) NPZ model and parameters appropriate for microzooplankton as opposed to larger grazers. Under these conditions, the model exhibits limit-cycle behavior which, when coupled to a 1-dimensional ocean model, exhibits spatio-temporal chaos. The patterns are strongly dependent on the magnitude of the vertical mixing. For very weak magnitudes of mixing (<10^-5 m^2/s), the system displays complex and quasi-periodic behavior. However, for realistic ocean values at and above the background internal wave level, the cycles become phase-locked over depth, the system reflects a low-order dimensionality, and does not show chaos. The stabilizing effect of diffusion using more conventional macrozooplankton parameters will also be discussed.

Day: Monday, Feb. 1

Time: 02:15 - 02:30pm

Location: Sweeney Center

Code: SS01MO0215S