Understanding the effects of climate change on planktonic ecosystems requires the synthesis of large, diverse data sets of variables that often interact in nonlinear ways. One fruitful approach to this synthesis is the use of numerical models. Here, we describe how models have been used to gain understanding of the physical-biological couplings leading to decadal changes in the southern California Current ecosystem. Moving from basin scales to local scales, we show how atmospheric, physical oceanographic, and biological dynamics interact to create long-term fluctuations in the dynamics of the California Current ecosystem.