Abstract:

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 it fluxes tracers between the depth and the surface. Recent work shows that this vertical transport preferentially occurs downstream of bottom topography, but this localized transport is not well described by the existing two-dimensional overturning theory. We address this gap by using an idealized Southern Ocean-like MITgcm channel and particle tracking in the thickness-weighted circulation to develop a new mechanistic understanding of the three dimensional-nature of the overturning. In addition, we run this model with simple biogeochemistry to investigate how the localized transport affects the carbon budgets. We find that air-sea carbon flux is enhanced over the topography, but is poorly sampled using Lagrangian floats (like those used in the Argo float program). The localization of the transport of carbon shows the necessity of careful modeling and sampling of these undersea ridges for a complete picture of carbon budgets and their variability.