A lack of winter sampling in the Southern Ocean has resulted in large gaps in our understanding of
the seasonal variability of primary productivity and consequently of the oceanic biological carbon pump. There is only one reported winter time distribution of dissolved iron (dFe, < 0.2 μm fraction), an essential
micronutrient that limits primary productivity in this oceanic region. This deficiency in seasonal
observations restricts our understanding of how Fe is supplied to surface waters in spring, when it
fuels primary production. More than 99% of dFe may be complexed by organic ligands in oceanic
waters but no winter time measurements of organic Fe concentrations have been published in the
Southern Ocean. The identity of these organic ligands remains largely elusive. It has been recently
proposed that humic substances may account for the entire ligand concentration in some oceanic
regions. Despite their potential to be a major player in the iron cycle, very few measurements of these
ligand types exist, and no data has ever been reported for the Southern Ocean. Furthermore, very few,
including no winter time, particulate Fe (pFe, > 0.45 μm fraction) measurements in the Southern
Ocean have been published, even though particulate Fe exerts controls on the dFe pool through
dissolution, scavenging and aggregation processes. We propose within this project, to investigate for the first time, the oceanic distributions of dFe, pFe, Feorg and humic substances simultaneously in the Atlantic Sector of the Southern Ocean in Winter 2019; onboard the South African RV SA Agulhas II (collaboration with CSIR and Stellenbosch University, South Africa).
SeaTraM arose within the framework of the Laboratoire Mixte International ICEMASA (International Centre for Education, Marine and Atmospheric Sciences over Africa), which facilitated the emergence of French-South African research projects on Climate Change in the Southern Ocean and African margins. The objectives of SeaTraM are also linked to the themes developed by the international GEOTRACES program, iron being a core parameter of GEOTRACES.