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Stochastic methods to quantify the effect of environmental variability on plankton ecosystems
Cullen, J. J.
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The marine physical environment is often dominated by seasonal, annual or longer cycles of variability. Higher frequency events caused by local weather and mesoscale hydrodynamic processes also exist and invoke biological reactions. Physical models can resolve this high-frequency variability through time-dependent forcing, which may be derived from observations. The results from plankton models coupled to physical models that resolve high-frequency variability are specific to the exact forcing time series used. Recent application of Monte Carlo methods to marine ecosystem modeling quantify how environmental variability propagates to biological variability by fitting error statistics to simulation results. This talk presents the result of simulations of a plankton model forced with random realizations of a physical time series which contain a periodic signal and randomly generated noise. The results are presented in the form of probability distributions that evolve over the cycle of the periodic signal. Two major findings are reported. First, the average time series from all realizations does not equal the solution of the model forced with the average of the random time series. Second, the interaction of a nonlinear (biological) system with random environmental fluctuations and periodic forcing causes emergent behavior, which can not be derived from classical model analysis.
Lehmann, M., and J. J. Cullen. "Stochastic methods to quantify the effect of environmental variability on plankton ecosystems." 39th CMOS Congress 2005 - Sea to Sky, Vancouver, British Columbia (Canada), May 31 - June 3, 2005.