Diffusion of Circumpolar Deep Water Towards Antarctica

Abstract

Throughout the Antarctic Circumpolar Current (ACC), mesoscale eddies transport water masses across time-mean streamlines, comprising the adiabatic pathway of the global meridional overturning circulation (Cessi, 2019;Marshall & Radko, 2003). Isopycnal eddy diffusion is fundamental for the poleward heat flux across the ACC because bottom-enhanced diapycnal mixing (Kunze et al., 2006) and surface water transformation (Abernathey et al., 2016) are unlikely to penetrate the intermediate and deep layers. Recent observations have indicated that mesoscale eddies play a key role in bridging the Antarctic meridional overturning from deep ocean basins to continental shelves (e.g., Mckee et al., 2019;Yamazaki et al., 2021), but its regime transition and transporting flux from the ACC to the Antarctic Slope Current (ASC) largely remains unknown from an observational standpoint (Thompson et al., 2018).Circumpolar Deep Water (CDW), the primary source of heat and salt for the Antarctic coasts, is transported across the ASC predominantly by mesoscale eddies in the absence of large-scale zonal pressure gradients (Stewart &