Multidecadal Changes in Southern Ocean Ventilation since the 1960s Driven by Wind and Buoyancy Forcing

Abstract Enhanced Southern Ocean ventilation in recent decades has been suggested to be a relevant modulator of the observed changes ocean heat and carbon uptake. This study focuses on midlatitude from 1960s 2010s. A global 1/4° configuration NEMO–Louvain-la-Neuve sea ice model, version 2 (LIM2), including inert tracer CFC-12 (a proxy ventilation) is forced with CORE, phase II (CORE-II), JRA-55 driving (JRA55-do) atmospheric reanalyses. Sensitivity experiments, where variability wind stress and/or buoyancy forcing suppressed interannual time scales, are used unravel mechanisms changes. Ventilation estimated by comparing interior inventories among different experiments. All simulations suggest multidecadal fluctuation ventilation, decrease until 1980s–90s subsequent increase. evolution related caused (often counteracting) effects forcing. Until 1980s, increased gains decrease, whereas increase was driven strengthened causing deeper mixed layers stronger meridional overturning circulation. Wind emerges as main driver changes, even though modulates its trend decadal variability. The three basins take up distinct density intervals but overall respond similarly suggests that expected long effect increasing Hemisphere overwhelms stratification.