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Abstract

The lower limb of the Meridional Overturning Circulation fills the abyssal ocean across much of the globe with Antarctic Bottom Water (AABW). However, this abyssal overturning cell only outcrops in the Southern Ocean; it depends upon rapid water mass transformation that occurs in a small number of distinct sites near the Antarctic continent, coupled with export of dense water from the Antarctic continental shelf. This strong dependence on local processes has compromised the fidelity of global models in representing the abyssal overturning - particularly for low-resolution climate models. Recent advances in high-resolution global ocean-sea ice models has led to significant improvements in model representation of AABW processes and has allowed deeper investigation into the dynamics of the lower cell of the MOC. In this presentation I will review recent progress in using high-resolution models to understand the dynamics of dense water export from the Antarctic, the sensitivity of dense water formation and the abyssal MOC to surface forcing, the variation of the AABW export and the pathways of AABW throughout the deep ocean. These advances help to constrain future potential changes in the lower overturning cell, and suggest methods to diagnose change from observations.