Presenter: Madeleine Youngs (NYU)

Description:
The Southern Ocean plays a major role in the global air-sea carbon fluxes, with some estimates suggesting it takes up 40\% of the oceanic anthropogenic carbon dioxide. Understanding the Southern Ocean overturning transport is particularly important because the overturning transport fluxes tracers between the depth and the surface.  Recent work shows that this vertical transport preferentially occurs downstream of bottom topography, but there is further work to understand how this relates to the theory of overturning circulation. This study uses an idealized Southern Ocean-like MITgcm channel and particle tracking in the thickness-weighted circulation to develop a new understanding of the three dimensional-nature of the overturning.  This study evaluates the overturning transport by splitting the flow into three main driving forces behind the transport.  First, is a wind-driven Ekman transport which is spread out throughout the domain and only leading order in the upper overturning cell, although not entirely zonally-symmetric due to the meandering nature of the flow. The remaining two components are standing eddies and transient eddies both of which are localized near the topography. The existence of the ridge weakens the response of the overturning to changes in wind, especially in the lower cell.  The localization of the vertical flow shows the necessity of careful modeling of these specific regions in the Southern Ocean to understand the transport and carbon export.