Seasonal and interannual variability of Antarctic Bottom Water
Polina Sholeninova
Antarctic Bottom Water (AABW) is a cold, dense water mass formed around Antarctica that ventilates the global abyssal ocean. While recent studies have reported widespread warming, freshening, and thinning of AABW, its seasonal and interannual variability beyond the shelf remains poorly constrained due to sparse and infrequent observations. We address this gap using the high-resolution ocean–sea ice model ACCESS-OM2-01, which realistically captures AABW pathways and variability. Dye-like passive tracers are released in four key source regions: the Weddell and Ross Seas, Adélie Land, and Prydz Bay. Seasonal variability is strongest in AABW from narrow-shelf Adélie and Prydz regions, while interannual variability dominates in AABW from the Ross and Weddell Seas. Only variability from Adélie and Prydz-sourced AABW penetrates into the abyss, while variability of AABW from the Ross and Weddell Seas remains largely confined to their along-slope pathways. Advective timescales also differ: Adélie and Prydz-sourced AABW descends to the abyss within 1–2 years, while Weddell and Ross-sourced AABW follow the continental slope for 2–3 years before descending. These findings provide new context for interpreting deep-ocean changes, helping to ensure that observed trends are robust to natural variability and to the spatial and temporal limitations of historical sampling.
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