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 regimes is used in a simple model to calculate the annual amount of dust deposited to the surface ocean. Calculated values range from 0.015 to 9.9 g dust m(-2) yr(-1). Comparison of these calculated dust depositions with independent dust deposition estimates obtained from direct measurements, suspended atmospheric dust loads, or sediment traps show remarkably good agreement over approximately 3orders of magnitude. In regions where the agreement between the model and other estimates is weakest, it is anticipated that local scaling of model parameters such as mixed layer depth and surface water residence time, will lead to improved agreement. Since surface water Al concentrations appear to be driven primarily by dust deposition, the distribution of dissolved Al in surface waters can be used to investigate the systematics of the delivery of other biologically important trace elements, for example, Fe, to the surface of the remote ocean by this route. In addition, temporal variations in surface water Al concentrations can be used to investigate the biogeochemical consequences to the surface ocean of large-scale changes in atmospheric dust loads driven by decadal-scale climatic variations.