Natural Variability of Antarctic Bottom Water in the Pre-Industrial CESM-HR simulation

Antarctic Bottom Water (AABW) plays a crucial role in the intensity and variability of the Global Overturning Circulation (GOC). AABW formation sustains the lower cell of the GOC, fundamentally regulating the storage and transport of heat and carbon, key properties influencing Earth’s climate. Changes in AABW have far-reaching implications for the stability of the GOC. However, the mechanisms governing the variability and potential changes in the strengthening of the AABW cell remains uncertain. Understanding the variability of AABW is crucial for projecting changes in ocean circulation and assessing associated climate impacts. This study aims to use the outputs of the high-resolution Community Earth System Model (CESM-HR) pre-industrial run to explore AABW natural variability and water mass transformation processes governing its formation. By analyzing the pre-industrial run, we aim to characterize baseline dynamics in the absence of anthropogenic forcing, focusing on how atmospheric variability drives changes in AABW properties and transport. Additionally, we investigate the role of surface cooling and salinization in shaping AABW characteristics through a water mass transformation framework. While small-scale processes are not fully resolved, CESM-HR offers an improved perspective on large-scale patterns and variability compared to coarser-resolution models. This study aims to provide insights into the baseline state of AABW dynamics under pre-industrial conditions. The results are expected to provide an enhanced understanding of AABW variability, offering insights into anthropogenic impacts and underscoring the need for complementary observational and modeling efforts to refine our understanding of AABW formation.