Melting of the Antarctic ice sheet and its surrounding ice shelves is accelerating, however most coupled climate models do not simulate this increasing freshwater flux, neglecting important climate impacts. To address this gap, the Southern Ocean Freshwater Input from Antarctica (SOFIA) Initiative established a coordinated multimodel framework to quantify the impacts of Antarctic meltwater. To date, the SOFIA community has implemented a standardised, idealised freshwater forcing across 13 coupled climate models. Multimodel analyses demonstrate that the impacts of Antarctic meltwater extend from the deep ocean to the stratosphere, and from high latitudes to the tropics. Surface freshening increases Southern Ocean stratification, driving surface cooling, an expansion of Antarctic sea ice, and subsurface warming that could accelerate ice shelf mass loss in East Antarctica. This enhanced stratification also suppresses Southern Ocean deep convection and Antarctic Bottom Water formation. The climatic consequences extend far beyond the high-latitude ocean: increased sea ice drives a tropospheric cooling and stratospheric warming, while oceanic and atmospheric teleconnections cool the equatorial Pacific. Collectively, the SOFIA simulations underscore the critical need to incorporate an interactive ice sheet into climate models to improve the accuracy of future global climate projections.