Input and cycling of iron in the Gulf of Aqaba, Red Sea

The Gulf of Aqaba, northern Red Sea, is an ideal natural laboratory for studying the impact of atmospheric dry deposition of iron to the ocean surface. We have measured atmospheric iron deposition weekly for 18 months, and dissolved and total dissolvable iron concentrations in the stratified summer (August) and well-mixed winter (March) water column. Concentrations of dissolved and total dissolvable iron remain roughly constant with depth in March. In August, there is a strong surface enrichment of iron. The accumulation of iron at the surface during the rain-free summer can be simulated by a one-dimensional model including atmospheric iron flux and estimates of iron scavenging, biological uptake and dissolution. An overall dissolution of 2% of dry deposited aerosol iron produces the best fit to the observations. A residence time of half a year for dissolved iron in surface waters with respect to scavenging is calculated for this region.