Fluxes of nutrients in a three-dimensional meander structure of the Antarctic Polar Front

The horizontal and vertical advection and the vertical diffusion of two plant nutrients (nitrate and silicate) are estimated at the Antarctic Polar Front (APF) in the Atlantic sector using quasi-synoptic, high-resolution physical and chemical measurements. Our results suggest that the routes of nutrient supply are more complex than indicated by existing large-scale views. The vertical advection associated with mesoscale upwelling events is shown to be between two and three orders of magnitude larger than the diffusion, and to potentially amount to the phytoplankton uptake rate locally. Averaged over the survey area, however, the vertical nutrient transport is downward and concords with the front acting as a barrier to the northward export of surface nutrients by the Ekman drift. This poses significant constraints on the global cycles of nutrients and may have an impact in the sediment record.