Uplift rates up to 40 mm yr⁻¹ are measured by GNSS in the southern Patagonian Icefield, a remainder of the Patagonian Ice Sheet that covered the Andes in the Last Glacial Maximum (LGM) at 26 ka. Using numerical modelling, we estimate an increase of 150 to 200 °C of the asthenospheric temperature due to the slab window under southern Patagonia, and we show that post-glacial rebound, after the long-term LGM and the short-term Little Ice Age (400 a), contributed to the modern uplift rate budget.