Extended Data Figure 3: Effect of Southern Ocean warming on Antarctic surface air temperatures and the ice sheet at 128 kyr ago.

a–c, January (warmest monthly mean) differences in 2-m surface air temperature at 128 kyr ago, relative to a preindustrial control simulation (top row). GHG, greenhouse gas; SST, sea surface temperature. d, e, Ice-sheet thickness (m) after 5,000 model years, driven by the corresponding climate in a–c. a and d, Without climate–ice sheet coupling (present-day ice extent and surface ocean temperatures in the RCM), and prescribed 5 °C sub-surface ocean warming felt only by the ice sheet. b and e, With asynchronous coupling between the RCM atmosphere and ice sheet, and prescribed 5 °C sub-surface ocean warming felt only by the ice sheet. c and f, With asynchronous coupling between the RCM atmosphere and ice sheet, prescribed 3 °C sub-surface ocean warming felt by the ice sheet, and ~2 °C surface ocean warming felt by the RCM atmosphere. c shows the locations of East Antarctic ice cores (EDC, EPICA Dome C; V, Vostock; DF, Dome F; EDML, EPICA Dronning Maud Land) indicating warming early in the interglacial²⁹ and previously attributed to WAIS retreat⁸⁰; this warming is similar to that simulated in c from a combination of ice-sheet retreat and warmer Southern Ocean temperatures, supporting the notion that the timing of LIG retreat was largely driven by far-field ocean influences, rather than local astronomical forcing.