High-Frequency Fluctuations in Antarctic Bottom Water Transport Driven by Southern Ocean Winds

Northward flow of Antarctic Bottom Water (AABW) across the Southern Ocean comprises a key component of the global overturning circulation. Yet AABW transport remains poorly constrained by observations and state estimates, and there is presently no means of directly monitoring any component of the Southern Ocean overturning. However, AABW flow is dynamically linked to Southern Ocean surface circulation via the zonal momentum balance, offering potential routes to indirect monitoring of the transport. Exploiting this dynamical link, this study shows that wind stress (WS) fluctuations drive large AABW transport fluctuations on time scales shorter than similar to 2 years, which comprise almost all of the transport variance. This connection occurs due to differing time scales on which topographic and interfacial form stresses respond to wind variability, likely associated with differences in barotropic versus baroclinic Rossby wave propagation. These findings imply that AABW transport variability can largely be reconstructed from the surface WS alone.

Automated summary

The transport of Antarctic Bottom Water is influenced by wind stress fluctuations, which drive fluctuations in transport on time scales shorter than 2 years, mainly due to differences in response time scales of topographic and interfacial form stresses to wind variability. This implies that the transport variability of Antarctic Bottom Water can largely be reconstructed from surface wind stress alone.