Observations indicate that Antarctic Bottom Water (AABW) has contracted in volume due to ice sheet melting. As a key component of the global ocean overturning circulation, this contraction is expected to be accompanied by global circulation adjustments. However, climate model simulations show that overturning responses to Antarctic meltwater input are largely confined to the high-latitude subpolar region. To uncover the dynamics associated with this overturning adjustment, we use an idealized configuration of MITgcm to conduct a suite of process-oriented simulations. Our results show that the overturning adjustment is strongly constrained by bottom topography, which supports coherent isopycnal adjustment through wave propagation. The deepening of isopycnals along meridional boundaries drives a slow-down of abyssal overturning, which weakens toward low latitudes to balance basin-scale isopycnal deepening. In the Antarctic Circumpolar Current (ACC) region above major topography, enhanced transient eddy transport compensates for the weakening of ACC meandering, thereby suppressing upper-ocean responses. These results highlight the role of topography in constraining overturning circulation responses to changes in surface forcing.
 

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