Characterization of Physical and Biogeochemical Variability around the Kerguelen Plateau and across the Southern Ocean Frontal Zones: A Machine Learning Approach

The Kerguelen Plateau (KP) region in the Indian sector of the Southern Ocean is a hotspot for energetic dynamics, which contribute to the mixing and stirring of heat, salt, carbon and nutrients throughout the water column. Core and biogeochemical (BGC) Argo floats data are used to investigate the impact of KP on the spatial variability of the physical and BGC properties of the Antarctic Intermediate Water (AAIW) and Upper Circumpolar Deep Water (UCDW). Using an unsupervised classification method applied to temperature and salinity float data, each float profile is automatically organized into its most likely Southern Ocean frontal zone. The algorithm not only automatically classifies the profiles into their zone based on similar properties, but it is also useful to identify regions where larger mixing might occur, e.g. in the mode water formation region, in the Agulhas current, and along fronts. We find that at fronts, eddies facilitate the intrusion and mixing of different waters, which enhance the variability of AAIW and UCDW and modify their properties. In particular, AAIW and UCDW show a transition from west to east of KP, where turbulence associated with KP acts to homogenize these changes.