Physical Modeling of Nutrient Upwelling

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Phytoplankton receive energy from the sun (from above), and nutrients from the water column (from below). Molecular diffusion proceeds so slowly that primary producers in the euphotic zone would deplete their nutrient resources over a time scale which is well below what is observed through experiments. They must, therefore, depend sensitively on the replenishment of nutrients through upwelling processes. There are large nutrient stocks at depth due to the constant death and decomposition of organisms that populate the euphotic zone. Thus a reliable model of phytoplankton population dynamics must incorporate an accurate physical model for the upwelling process. While work on this physical component has been undertaken by a small number of researchers, the general consensus among ocean biologists is that considerable work remains to be done. For instance, Bleck et al (1988) have shown the importance of fronts to the upwelling process using the MYCOM isopyncnal vertical grid model. For coastal upwelling, a "hybrid" version may be more suitable. However, the physics component must be supplemented by a suite of biological considerations such as the adaptivity of diatoms to variations in light; the role of zooplankton in limiting the phytoplankton populations; and the mobilities of nutrients, phytoplankton, and zooplankton. This biological component is currently beyond the PI's realm of expertise, and it is through collaboration with Dr. Gary Hitchock at the Rosenstiel School that useful predictive models will be forged. This IGMS project is jointly supported by the MPS Office of Multidisciplinary Activities (OMA) and the Division of Mathematical Sciences (DMS).