Recent numerical model results focussed on the Southern Ocean meridionaloverturning support the observationally derived formation rate of denseAntarctic Bottom Water (AABW) of the order of 10 Sv, mainly confined tothe Atlantic sector of the Southern Ocean. The numerically derived ratedoubles if a slightly lighter component of the Indian-Pacific (IP) sector isincluded, supporting the hypothesis that the sources in the southern andnorthern hemisphere contribute equally to the ventilation of the worldocean abyss. Most of the estimates based on observations, however,repesent long-term means which do not reflect the seasonal andinterannual variability inherent to the bottom water formation process.