"What Controls the Surface Ocean Iron Distribution? A Modeling Study".

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

ABSTRACT OCE- 0350672 There is an increasing awareness of the key role of iron in ocean biogeochemical cycles, limiting primary production and potentially limiting export and nitrogen fixation. Due to increasing knowledge of distribution and speciation of oceanic iron, and of the processes that control it, it is timely to develop and examine numerical models of the ocean iron cycle. Numerical models provide one means by which to encapsulate the communities understanding of biogeochemical cycles and examine if this understanding is consistent with the available data (i.e. can the model reproduce the key features of the data). Such models may also be used to explore the sensitivities of the system to changes in forcing, parameterizations or parameter values. In this study, researchers at the Massachusetts Institute of Technology will continue the preliminary model studies by further developing, constraining, and exploring numerical models of the ocean iron cycle with the framework of a three-dimensional ocean GCM. The team of scientists will perform sensitivity tests to determine which are the most significant processes and how they respond to changing physical and biogeochemical forcing. Specifically, five chemical, physical and biological questions will be addressed: what are the optimal conditional stability constants and scavenging rates which bring the complexation based iron model into consistency with observed data; can the effects of surface photochemistry, the formation of colloids, and precipitation of iron be parameterized; do these processes have a significant role in setting the distribution and availability of iron; what is the impact of regionally varying availability (or solubility) of iron of aeolian origin; how sensitive is the surface distribution of iron and phosphorus to the veracity of the modeled ocean circulation; is the distribution of iron sensitive to details of the interactions of the ecosystem and multiple potentially limiting nutrients. As the culmination of this study a "best-shot" circulation and iron biogeochemistry model will be used to examine the role of time-varying physical and biogeochemical forcing and boundary conditions in modulating the ocean iron cycle. Finally, the team of scientists will examine the consequences for ocean biogeochemistry and air-sea gas fluxes.