Abstract

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 uses a dynamically self-consistent ocean state estimate (ECCOV4r4) to show that wind stress fluctuations drive large AABW transport fluctuations on time scales shorter than ~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 vs. baroclinic Rossby wave propagation. These findings imply that AABW transport variability can largely be reconstructed from the surface wind stress alone.