Impact of paleocirculations on the silicon redistribution in the world ocean

A global biogeochemical ocean general circulation model with a representation of the marine silicon (Si) cycle including the bioturbated sediment zone is integrated into full equilibrium including for four different velocity fields: One preindustrial circulation under partial use of forcing data from an atmospheric model, one preindustrial circulation under use of climatological atmospheric forcing fields from measurements only, a circulation representing Last Glacial Maximum conditions, and one circulation reflecting the mid-Miocene ocean with an open Panama isthmus. Results of paleo-simulations are compared with a paleoceanographic sediment data base for opal. Marine Si budgets for the glacial and pseudo mid-Miocene oceans are presented under the same biogeochemical forcing. It turns out that the sediment distribution reacts sensitively to a switch between velocity fields while the overall budgets and fluxes between Si cycle compartments change only to a minor degree. This indicates that opal sediment has a considerable potential as a paleoceanographic tracer for ocean circulation and biological productivity.