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The Localization by Topography of the Three-Dimensional Overturning Circulation of the Southern Ocean and Its Implications
  • Madeleine K. Youngs,
  • Glenn R. Flierl
Madeleine K. Youngs

Corresponding Author:my2368@nyu.edu

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Glenn R. Flierl
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The Southern Ocean plays a major role in the global air-sea carbon fluxes, with some estimates suggesting it contributes to up to 40\% of the oceanic anthropogenic carbon dioxide uptake, despite only comprising 20\% of oceanic surface area. Thus the Southern Ocean overturning transport, the circulation that transports tracers between the surface and the interior, is particularly important for climate. Recent studies show 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 and localized nature of the overturning, splitting the flow into three main drivers of the transport. The first component is a wind-driven Ekman pumping into or out of a density layer; it is primarily but 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. Localization of the vertical flow shows the necessity of careful modeling these specific regions in the Southern Ocean to understand the transport, carbon export, and the connection with the oceans to the north.