This study uses evaporitic carbonates to understand how and when locations across Antarctica experienced surface melting over the past 100,000 years. We use the isotopic composition of thin layers of carbonate that formed on rocks across Antarctica, which form when snow melts, evaporates, and concentrates salts in waters to the point of saturation for the mineral calcite. By dating these carbonate layers and analyzing their isotopes, we show that melting was triggered by periods of intense solar radiation caused by Earth’s changing orbit—specifically, during times when Earth’s precession drove an increase in the amount of solar energy reaching the South pole. This suggests that small changes in solar radiation can tip the balance toward melting, especially on dark rocky surfaces that absorb heat. These findings help understand the mechanisms through which evaporative carbonates can form on the surface in polar environments and how ice sheets can experience melting under cold conditions, which improves our understanding of how Earth's orbital cycles affect global ice volume through time.