The large-scale upwelling in the Southern Ocean provides a pathway for the deep and abyssal water masses of the global ocean to return to the surface, creating a mechanism for the exchange of carbon and heat between the deep ocean and the atmosphere. Despite the significance of the overturning circulation in the Southern Ocean for global climate, very little is known about the three-dimensional nature of the overturning pathways and of the associated meridional transports of heat and salt. We aim to map the longitudinal and vertical structure of the upwelling pathways in the Southern Ocean, using combined Lagrangian and Eulerian analyses. We will use a range of GFDL and CCSM4 model configurations and simulations and evaluate the modeled overturning pathways against observational velocity estimates constructed using data from the Argo array of profiling floats. Our model analyses will allow us to explore the degree of dynamical interconnection or separation between the pathways of the upper and abyssal overturning cells and the sensitivity of this to different climate forcing. The impact of changes in the Southern Ocean overturning circulation on heat and carbon uptake and sea level change will be diagnosed by comparing spatial patterns of temperature, salinity and carbon anomalies to changes in the three-dimensional structure of the overturning pathways, in addition to detailed heat and salt flux budget analyses.By comparing a hierarchy of model simulations with coarse to eddy-rich ocean resolution, and evaluating these models against a novel observational data set, the proposed research will provide valuable information to the scientific community’s model development efforts regarding the ocean resolution required to sufficiently simulate future climate change. This proposal is a collaborative effort between Princeton University, Los Alamos National Laboratory and the Geophysical Fluid Dynamics Laboratory/NOAA.