Dissolved Fe and Mn During the A16S CLIVAR Repeat Hydrography Transect in the South Atlantic

Shipboard dissolved Fe and Mn were determined on samples collected using a trace metal clean rosette as part of the US CLIVAR Repeat Hydrography program's A16S transect between 6 and 60˚S in the South Atlantic in Jan/Feb 2014. Elevated surface water concentrations of Fe and Mn in the equatorial region correspond to regions of elevated aerosol deposition, and subsurface values for both elements are also highest in this region. Further south both surface and subsurface concentrations of these elements decrease. Between 37 and 39˚S, concentrations of both parameters increase, coincident with the ship's track crossing the recirculating arm of the Brazil current as it heads east across the basin. South of this feature, surface and sub-surface Mn values drop rapidly while the vertically cycled biologically active Fe concentrations decline more slowly. At 48˚S, the Subantarctic Front, there is a large drop in the Mn concentrations but a somewhat lesser gradient in Fe. The island mass of South Georgia at 53-55˚S imprints a shallow maximum on the Mn and a smaller input of Fe.