Matter of glacial origin and its fate in the ocean: a case study at Kerguelen – MARGO

In the Southern Ocean, insufficient supplies of nutrients such as iron or silicon can affect the functioning of the biological carbon pump with large consequences on climate. Material of glacial origin (MGO) provided by the melting of ice caps represents one of the sources of these nutrients. But the role of MGO remains poorly studied in the Southern Ocean, both qualitatively (involved processes) and quantitatively (fluxes). Considering the accelerated melting of the sub-Antarctic and Antarctic ice caps, a better understanding of the fate of MGO is critical. MARGO aims to provide new fundamental knowledge on the main processes controlling the fluxes of MGO and their impact in the Southern Ocean by proposing an integrated study along the glacier-ocean continuum. The exceptional multidisciplinary knowledge that exists at Kerguelen and the accessibility of the sites make this region an ideal site for a first integrated study to characterize the origin, fate and impact of MGO in the Southern Ocean. MARGO is based on an ambitious multidisciplinary approach (glaciology, physics, geochemistry, microbiology) combining data acquisition (on land and at sea) and modelling. The modelling of the ice cap melting combined with geochemical measurements will allow to quantify the fluxes of MGO reaching the ocean at different time scales. Process studies dedicated to the determination of the bioavailability of MGO to marine microorganisms will allow to quantify the fraction of MGO that can actually impact the biological activity of the Southern Ocean. A lagrangian transport model will be used to study its transport and dispersion in the ocean and to compare the role of MGO to other sources at different spatial scales.