Katja Curtin: Understanding Southern Ocean heat and carbon ventilation to improve climate projections
The Southern Ocean is responsible for the largest fraction of anthropogenic heat and carbon uptake by the global oceans and has therefore played a vital role in moderating the effects of climate change over the past century. The transfer of heat and carbon from the surface to the ocean interior, through a process called ‘ventilation’, is critical to understanding future climate trajectories. Southern Ocean ventilation is controlled by a chain of interconnected mechanisms, including localised subduction, eddy-driven isopycnal mixing, lateral transport from subtropical gyre circulation, and meridional overturning (Morrison et al., 2022). However, projections of future Southern Ocean heat uptake, and the relative contributions from each ventilation mechanism remain highly uncertain. Utilising a suite of perturbation experiments with Australia’s latest ocean/sea-ice model, ACCESS-OM3, this research aims to develop a new fundamental understanding of the interconnected ocean processes that constrain carbon and heat transfer from the surface to the deep ocean. Four experiments are designed to perturb each ocean mechanism respectively, and thus offer insights into their connectivity. Ventilation is quantified using spatially uniform, surface-released passive dye tracers. The preliminary results from this study are particularly relevant to those interested in the development of ACCESS-OM3 for mid-latitude Southern Ocean research. By identifying the relative impact of each ventilation mechanism on mode water formation, this study seeks to explain how circulation, mixing, and subduction processes interact to govern Southern Ocean ventilation.