『（Abstract）
　The environmental conditions of Earth, including the climate, are determined by physical, chemical, biological, and human interactions that transform and transport materials and energy. This is the “Earth system”: a highly complex entity characterized by multiple nonlinear responses and thresholds, with linkages between disparate components. One important part of this system is the iron cycle, in which iron-containing soil dust is transported from land through the atmosphere to the oceans, affecting ocean biogeochemistry and hence having feedback effects on climate and dust production. Here we review the key components of this cycle, identifying critical uncertainties and priorities for future research.』

（Introduction）
Climate effects on dust/iron fluxes
Dust/iron impacts on the ocean
Effect on climate of iron inputs to the oceans
Global iron connections
References and Notes
(Acknowledgements)

Table 1. Global iron fluxes to the ocean (in Tg of Fe year^-1). From Poulton and Raiswell (4), with modified atmospheric inputs from Fig. 2. "Authigenic fluxes" refer to releases from deep-sea sediments during diagenesis. We distinguish only separately dissolved and particulate for fluvial inputs, because it is clear that fluvial particulate iron, along with iron from coastal erosion and glacial sediment sources, does not reach the oceans, whereas authigenic, atmospheric, and hydrothermal iron all reach the oceans regardless of their phase.

Source	Flux
Fluvial particulate total iron	625 to 962
Fluvial dissolved iron	1.5
Glacial sediments	34 to 211
Atmospheric	16
Coastal erosion	8
Hydrothermal	14
Authigenic	5

Fig. 1. Schematic view of global iron and dust connections. Highlighted are the four critical components (clockwise from top): the state of the land surface and dust availability, atmospheric aerosol loading, marine productivity, and some measure of climatic state (such as mean global surface temperature). The sign of the connections linking these varies; where the correlation is positive (for example, increased atmospheric aerosol loading→increased marine productivity), the line is terminated with a solid arrowhead. Where the correlation is negative (for example, increased marine productivity→lower CO2 and a colder climate), the termination is an open circle. Connections with an uncertain sign are terminated with an open arrowhead. The mechanism by which the link acts (for example, the impact of a change in atmospheric CO2 is via the radiative forcing of climate) is displayed in italics. Finally, the "water tap" symbols represent a secondary mechanism modulating the effect of a primary mechanism; for instance, a change in global precipitation strength and distribution will alter the efficiency with which entrained dust is transported to the open ocean. If a path of successive connections can be traced from any given component back to itself, a closed or feedback loop is formed. An even number (including zero) of negatively correlated connections counted around the loop gives a positive feedback, which will act to amplify a perturbation and tend to destabilize the system. Conversely, an odd number of negative correlations gives a negative feedback, dampening any perturbation and thus stabilizing the system. For instance, atmospheric aerosol loading→marine productivity→climatic state→dust availability→atmospheric aerosol loading contains two negative and two positive correlations and thus is positive overall. In contrast, marine productivity looping back onto itself contains a single negative correlation and thus represents a negative feedback. 〔Jickells,T.D., An,Z.S., Andersen,K.K., Baker,A.R., Bergametti,G., Brooks,N., Cao,J.J., Boyd,P.W., Duce,R.A., Hunter,K.A., Kawahata,H., Kubilay,N., laRoche,J., Liss,P.S., Mahowald,N., Prospero,J.M., Ridgwell,A.J., Tegen,I. and Torres,R.(2005): Global iron connections between desert dust, ocean biogeochemistry, and climate. Science, 308, 67-71.から〕

Fig. 2. Dust fluxes to the world oceans based on a composite of three published modeling studies that match satellite optical depth, in situ concentration, and deposition observations (11, 14, 15). The models have been extensively compared to observations, and although individual models show strengths and weaknesses, this composite appears to match observations well. Total atmospheric dust inputs to the oceans = 450 Tg year-1. Percentage inputs to ocean basins based on this figure are as follows: North Atlantic, 43％; South Atlantic, 4％; North Pacific, 15％; South Pacific, 6％; Indian, 25％; and Southern Ocean, 6％. 〔Jickells,T.D., An,Z.S., Andersen,K.K., Baker,A.R., Bergametti,G., Brooks,N., Cao,J.J., Boyd,P.W., Duce,R.A., Hunter,K.A., Kawahata,H., Kubilay,N., laRoche,J., Liss,P.S., Mahowald,N., Prospero,J.M., Ridgwell,A.J., Tegen,I. and Torres,R.(2005): Global iron connections between desert dust, ocean biogeochemistry, and climate. Science, 308, 67-71.から〕

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