Large scale nutrient fronts of the world ocean: impacts on biogeochemistry.

This chapter identifies and describes the large-scale nutrient fronts that span the width of basins and explores the processes that maintain these fronts and those that act against them. In particular, we investigate the nutrient fronts that ring the subtropical gyres and propose that exchange across these fronts represents a critical pathway for nutrients to enter the gyres. However, these biogeochemical fronts most often coincide with dynamical fronts or jets, which are often considered barriers to exchange. Therefore, our view of ocean fronts as nutrient gateways must be reconciled with their tendency to act as barriers to exchange. Ekman transport is one mechanism that allows for nutrient transport across the surface of the fronts and is shown to be a leading term in the subtropical nutrient budgets. Ring formation and mixing beneath the core of jets are other mechanisms that can mediate cross-frontal exchange and have intriguing implications for nutrient budgets and their variability.