Influence of the enhanced mixing within the Southern Ocean fronts on the overturning circulation

Observations indicate that turbulent mixing is enhanced in the major fronts of the Antarctic Circumpolar Current (ACC), penetrating through much of the water column. Here we employ a simple representation of this process in a global climate model to evaluate its potential impact on the ocean's overturning circulation. Two effects are obtained. First, the frontally-intensified mixing in the Southern Ocean increases the transformation of NADW to UCDW. Second, by intensifying the dense water upwelling in the south, the vertical mixing in the ACC fronts returns a fraction of the northward flowing AABW/LCDW as UCDW, consistent with recent observational results; the corresponding abyssal overturning weakens. The results are interpreted using a single-basin model.