Seasonal Meandering of the Polar Front Upstream of the Kerguelen Plateau

The location of the Antarctic Polar Front (PF) is mapped in the Southern Indian Ocean bydecomposing the shape of temperature and salinity profiles into vertical modes using a functional PrincipalComponent Analysis. We define the PF as the northernmost minimum of temperature at the subsurface andrepresent it as a linear combination of the first three modes. This method is applied on an ocean reanalysisdata set and on in situ observations, revealing a seasonal variability of the PF latitudinal position that ismost pronounced between the Conrad Rise and the Kerguelen Plateau. This shift coincides with variationsin the transport across the Northern Kerguelen Plateau. We suggest that seasonal changes of the upperstratification may drive the observed variability of the PF, with potentially large implications for thepathways and residence time of water masses over the plateau and the phytoplankton bloom extendingsoutheast of the Kerguelen Islands.