Dissolved Al in the A16S CLIVAR Repeat Hydrography Section and Its Implication for Aerosol Deposition in the South Atlantic

It has long been suggested that the Patagonian plateau is a source of enhanced mineral aerosol to the surface waters of the South Atlantic. The CLIVAR repeat hydrography A16S section provided an opportunity to examine this hypothesis by sampling water using a trace metal clean rosette from the upper 1,000 m between ~6˚- 60˚S in the Atlantic Ocean. The concentration of dissolved Al in the surface waters along this transect has been used in a simple box model to estimate aerosol deposition to these waters. The results show that atmospheric deposition in this region is fairly low, ranging from ~1.5 g m^-2 yr^-1 in the Saharan dust influenced equatorial region, to less than 0.1 g m^-2 yr^-1 at 47˚S. Subsurface dissolved Al values indicate a significant source from subducted equatorial waters and a region of enhanced concentrations centered at 36˚S coinciding with a minimum in potential vorticity, suggesting a sub-tropical mode water source. As seen elsewhere, there is a large decrease in concentrations at the subantarctic front. South of South Georgia, concentrations throughout the water column rise significantly, indicating additional sources to the Scotia Sea. The data set shows no evidence of correlation between dissolved Si and Al.