On the use of dissolved aluminum in surface waters to estimate dust deposition to the ocean

The concentration of dissolved Al in surface waters from various oceanic re gimes is used in a simple model to calculate the annual amount of dust depo sited to the surface ocean. Calculated values range from 0.015 to 9.9 g dus t m(-2) yr(-1). Comparison of these calculated dust depositions with indepe ndent dust deposition estimates obtained from direct measurements, suspende d atmospheric dust loads, or sediment traps show remarkably good agreement over approximately 3orders of magnitude. In regions where the agreement bet ween the model and other estimates is weakest, it is anticipated that local scaling of model parameters such as mixed layer depth and surface water re sidence time, will lead to improved agreement. Since surface water Al conce ntrations appear to be driven primarily by dust deposition, the distributio n of dissolved Al in surface waters can be used to investigate the systemat ics of the delivery of other biologically important trace elements, for exa mple, Fe, to the surface of the remote ocean by this route. In addition, te mporal variations in surface water Al concentrations can be used to investi gate the biogeochemical consequences to the surface ocean of large-scale ch anges in atmospheric dust loads driven by decadal-scale climatic variations .