24th Pacific Science Congress (PSC-24)

The central Ross Sea slope (CRSS) is a critical region for water mass exchange, significantly influencing the physical and biological processes of the Ross Sea shelf and global overturning circulation. This study utilizes a high-resolution ocean-ice shelf-sea ice coupled model to investigate the mechanisms driving this exchange, involving the onshore transport of Circumpolar Deep Water (CDW) and the offshore transport of Dense Shelf Water (DSW). Combining numerical simulations and mooring observations, this work reveals high-frequency oscillations with a periodicity of ~32 hours in CDW transport induced by Topographic Rossby Waves and DSW transport induced by cyclonic eddies. These findings provide evidence for earlier theoretical work using idealized models that suggest such oscillations. Meanwhile, we found that the net cross-slope transport is dominated by the low-frequency processes, the contributions of which are quantified using momentum diagnostics. The DSW outflow is driven by bottom Ekman transport linked to the strong Antarctic Slope Current (ASC), as significant as interfacial form stress in previous studies. Sea surface height gradient, resulting from the displacement of less dense water by the DSW in the bottom layer, can drive the onshore transport of CDW. While such DSW-CDW transport relation bears similarity to that proposed by previous work focusing on continental troughs, we found that on the slope, the CDW onshore transport is also modulated by baroclinic pressure gradient resulting from density variations and by horizontal advection associated with the spatial variation of ASC. These findings enhance the accuracy of water mass exchange estimates across the CRSS.
 

Ross Sea,Circumpolar Deep Water,Dense Shelf Water