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Abstract Antarctic bottom water (AABW) forms through the descent of dense shelf waters (DSW) into the abyssal ocean, with tides playing a key role in DSW transport and entrainment. Previous studies suggest that tides can suppress the net overflow entrainment, favoring the formation of denser AABW. However, how tidal effects on AABW formation and associated material sequestration vary with a changing climate remains unclear. In this study, an idealized numerical model is used to investigate potential climatic influences on tidally influenced AABW properties. Experiments are conducted with varying ambient stratifications and rates of DSW supply, inspired by projected future changes over the Antarctic continental shelf. The results show that tidal advection and associated V‐shaped front can modify the vertical diffusivity and the exchanges between DSW and its ambient waters, thereby altering the properties of AABW. For a future warm and salty shelf, AABW will become warmer and saltier accordingly, with the effects of the V‐shaped front weakening significantly. Conversely, for a future cold and fresh shelf, AABW formation is nearly nonexistent due to the stronger dilution of DSW, and the tidal effects become much weaker. Additionally, tidal suppression of overflow mixing is only significant for large DSW fluxes (thickness) and becomes negligible for small DSW fluxes. These findings suggest that the contribution of tides to DSW descent will weaken under global warming, thereby accelerating the slowdown of AABW formation. 

Abstract Antarctic Bottom Water is primarily formed via overflows of dense shelf water (DSW) around the Antarctic continental margins. The dynamics of these overflows therefore influence the global abyssal stratification and circulation. Previous studies indicate that dense overflows can be unstable, energizing topographic Rossby waves (TRW) over the continental slope. However, it remains unclear how the wavelength and frequency of the TRWs are related to the properties of the overflowing DSW and other environmental conditions, and how the TRW properties influence the downslope transport of DSW. This study uses idealized high-resolution numerical simulations to investigate the dynamics of overflow-forced TRWs and the associated downslope transport of DSW. It is shown that the propagation of TRWs is constrained by the geostrophic along-slope flow speed of the DSW and by the dynamics of linear plane waves, allowing the wavelength and frequency of the waves to be predicted a priori. The rate of downslope DSW transport depends nonmonotonically on the slope steepness: steep slopes approximately suppress TRW formation, resulting in steady, frictionally dominated DSW descent. For slopes of intermediate steepness, the overflow becomes unstable and generates TRWs, accompanied by interfacial form stresses that drive DSW downslope relatively rapidly. For gentle slopes, the TRWs lead to the formation of coherent eddies that inhibit downslope DSW transport. These findings may explain the variable properties of TRWs observed in oceanic overflows, and they imply that the rate at which DSW descends to the abyssal ocean depends sensitively on the manifestation of TRWs and/or nonlinear eddies over the continental slope.