Biogeochemistry of iron in Australian dust: From eolian uplift to marine uptake

Abstract

Dust is an important vector for iron supply to the ocean, which subsequently impacts ocean productivity, atmospheric CO2 concentrations, and hence global climate. Here, we synthesize the processes influencing the biogeochemistry of Australian dust and compare them with those from other Southern Hemisphere dust sources. Our observations range from soil and dust physical properties to abrasion and cloud chamber chemistry experiments to dust storms and their dispersion and deposition. We then present satellite observations of the impact of episodic dust deposition events on the productivity of low-iron oceanic waters north (i.e., low-nitrate, low-chlorophyll (LNLC)) and south (i.e., high-nitrate, low-chlorophyll (HNLC)) of Australia. Dust deposition from the largest dust storm in over 40 years did not result in iron-mediated algal blooms in either oceanic region. A comparison of Australia with other Southern Hemisphere source regions reveals that the relatively well sampled Australian system is a poor generic model. Furthermore, there are marked distinctions between Southern and Northern Hemisphere iron/dust biogeochemistry that must be recognized by modelers and included in future simulations. Better information is required on the relative role of the atmosphere and ocean on influencing iron biogeochemistry and how their relative influences might change in the future due to climate change.