As the densest water mass in the abyssal ocean, Antarctic Bottom Water (AABW) occupies more than one-third of the global ocean volume and constitutes the lower limb of the global meridional overturning circulation. The production and properties of AABW are largely determined by Dense Shelf Water (DSW) that is formed by intense sea ice formation and brine rejection in coastal polynyas around Antarctica. As the precursor water mass, DSW cascades down the continental slope after crossing the shelf break, entrains ambient deep water, and ultimately transforms into AABW. Beyond driving abyssal circulation, these dense water masses also play a major role in the transport and long-term storage of heat, carbon, oxygen, nutrients, and other biogeochemical tracers in the abyss, and further modulate the productivity of marine ecosystems and biogeochemical cycles. Exploring the dynamics and variability of DSW and AABW is essential to improve our understanding of the global heat distribution, carbon budgets, and long-term climate variability.
Observational evidence has revealed a widespread contraction in AABW volume across global abyssal waters. At the same time, changes in DSW and AABW properties are not spatially uniform around Antarctica, highlighting substantial uncertainty in their future evolution. This session aims to advance a comprehensive and process-based understanding of AABW, bridging gaps between DSW and AABW transport, formation, transformation, and variability mechanisms, and corresponding impacts on climate variability and change and biogeochemical cycles. To encourage broad participation, we welcome contributions based on in-situ observations, remote sensing, and numerical simulations covering the full pathway from DSW formation and export to AABW transformation and spreading, with an emphasis on Ross Sea-originated DSW and AABW.