Stable water isotope signals in inland Antarctic ice cores have provided wealth of information about past climates. This study investigated atmospheric circulation processes that influence precipitation isotopes in inland Antarctica associated with atmospheric circulations in the southern mid-latitudes during the Last Glacial Maximum (LGM, ~21 000 year ago). We simulated this climate period using circulation model (MIROC5-iso) forced with different sea surface boundary conditions. Our results showed a steepened meridional sea surface temperature gradient in the southern mid-latitudes associated with a strengthening of the southern westerlies. This change in the atmospheric circulation enhanced the intrusion of warm and humid air from low latitudes that contributes to precipitation events, inducing heavy isotope precipitation inland East Antarctica. Our results suggest that the representation of past southern westerlies can be constrained using water isotopic signals in Antarctic ice cores.