Exploring the relationship between vertical mixing, overturning circulation, AABW volume, and ventilation age during the last glacial maximum

One interpretation of Last Glacial Maximum (LGM) paleo-environmental data is the expansion of poorly ventilated Antarctic Bottom Water (AABW) coinciding with weakened AABW overturning, which is reflected in few modelling efforts. This research addresses the relationship between vertical mixing, AABW volume, overturning circulation, and ventilation age using the UVic Earth System Climate Model with five vertical mixing parameterizations that differ in the value of diapycnal diffusivity in the deep ocean. In all simulations AABW volume and overturning strength increases during the LGM relative to pre-industrial (PI), with small differences between mixing schemes. All mixing schemes yield older bottom water during the LGM relative to PI, indicating that a decrease in overturning strength is not required to decrease ventilation age. Our results offer insights into the relationship between AABW overturning, volume, and ventilation, with little impact based on mixing scheme.