Exploring iron control on global productivity: "FePSi", an inverse model of the ocean's coupled phosphate, silicon and iron cycles

Abstract

“FePSi” is the first data-constrained mechanistic inverse model coupling the iron (Fe), phosphorus (P), and silicon (Si) oceanic cycles. The nutrient cycling is embedded ina data-assimilated steady global circulation. Biological nutrient uptake is parameterized in terms of nutrient, light, and temperature limitations on growth for 3 classes of phytoplankton that are not transported explicitly. A sparse matrix formulation of the discretized nutrient tracer equations allows for efficient numerical solutions using Newton’s method, which facilitates the objective optimization of the key biogeochemical parameters. The optimization minimizes the misfit between modeled and observed nutrients and chlorophyll fields. We explore the nonlinear, counterintuitive and asymmetric responses of the biological pump and nutrient cycles to changes in the aeolian iron supply for a variety of scenarios. Specifically, Green-function techniques are employed to quantify in detail the pathways and timescales with which those perturbations are propagated throughout the world oceans, determining the global teleconnections that mediate the response of the global ocean ecosystem.

Benoît Pasquier

Research Associate

My research interests include mathematics, oceanography, and computer science.