Geochemical Earth Reference Model -- GERM
The Purpose of GERM

The Earth is a dynamic planet and its current state is the product of a balance of chemical fluxes between terrestrial reservoirs, both large and small. These fluxes, and changes in them, established the "System Earth" over its 4.5 Gyr history and sustain its current habitability. Current and future changes of chemical fluxes in this system, therefore, may have a direct impact upon society.

Short-term climatic cycles are superimposed on and partly controlled by long-term, "geological" processes (0.1-5 Gyr). While the models of the former are reasonably mature, planetary geochemical models of the Earth relevant to geological time scales are still at relatively early stages of development. Such models are needed to provide a perspective and context for understanding shorter term changes, both natural (e.g., Milankovich cycles) and anthropogenic (e.g., greenhouse gases).

In the past, pathways between terrestrial reservoirs (e.g., crust, ocean mantle) have been studied only for specific aspects, such as the isotopic and trace element evolution of the mantle, crustal growth, etc., and often address only a specific time, e.g., the Cenozoic. Nevertheless, significant progress has been made in our understanding of the System Earth and has led to major international programs, such as ODP and (inter-)RIDGE.

Much is yet to be gained by integrating these models and inventories into truly planetary ones, and by promoting interaction between scientists working on different aspects of this problem. Only this can help us uncover discrepancies, gaps, and inconsistencies and identify research priorities. Discrepancies discovered this way should in turn both lead to improved model conception and trigger a reassessment of fluxes and transfer mechanisms between reservoirs. These considerations all converge on the need for establishing a Geochemical Earth Reference Model, analogous to geophysical reference models. Such a GERM, however, can only be established through a consensus amongst a diverse group of earth scientists that focuses on a physical and chemical aspects of the pathways between major terrestrial reservoirs.

This project aims to clarify the present status of global models and flux measurement projects. The specific objectives of this effort are to:

• Incorporate of our best understanding of the physics of transport into integrated reference models of long-term geochemical pathways.
• Establish "best estimates" of the chemical inventories of reservoirs and fluxes between them.
• Evaluate the sensitivity of models to uncertainties in fluxes.
• Evaluate and provide guidance to existing global flux research programs and to develop new initiatives.
• Explore the dynamics of linkages between components of a GERM.

A more comprehensive discussion of the goals and structure of this effort can be found on the GERM Initiative web page.