Seminar: The Southern Ocean Circulation and Climate: The Localizing Effect of Topography

Abstract

The Southern Ocean plays a major role in the global carbon dioxide balance; it draws down a disproportionally-large portion of human-caused carbon dioxide emissions. To understand this carbon budget, we investigate the vertical transport in the Southern Ocean because it fluxes tracers (like carbon) 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 theory. We address this gap by using an idealized Southern Ocean-like channel numerical model, with particle tracking in a circulation mathematically-equivalent to the full three-dimensional flow. This allows us 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 currently used to sample the Southern Ocean). 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, in order to fully understand the global carbon budget.