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Abstract

Antarctic Bottom Water (AABW) composes the lower limb of the meridional overturning circulation regulating the Earth's climate, carbon cycle and marine biological productivity. Recent studies have reported changes in AABW across the Southern Ocean, including freshening, warming and contraction of the AABW layer. Due to Antarctica's remoteness and harsh conditions, in-situ observations are limited and do not provide enough spatial and temporal coverage to fully reconstruct the circulation and variability of AABW. In contrast, the global ocean model ACCESS-OM2 provides high-resolution data and, unlike earlier models, represents the AABW formation more realistically. With a focus on the Australian-Antarctic Basin and varieties of AABW formed in the Ross Sea and near the Adelie Land coast, we investigate AABW export pathways and their variability in ACCESS-OM2 with a 0.1-degree horizontal resolution. We use the concentration and horizontal fluxes of passive dye tracers to determine the location of the pathways. Ross Sea Bottom Water is characterised by westward flow confined between 2000- and 3000-m isobaths with a downslope leakage around 135E and is traced as far west as 105E. Adelie Land Bottom Water is traced at the same depth but between 145E and 100E, with numerous downslope plumes along its westward flow. In addition, we study seasonal and inter-annual variability of AABW and its varieties in the Australian-Antarctic Basin to fill the gaps in observations. Quantifying the pathways from different AABW formation regions will help to identify the processes driving changes in the AABW layer observed in recent decades.