Marine Isotope Stage 31 (MIS-31) is one of the major interglacials of the early Pleistocene approximately 1.08 to 1.06 Ma. Data from proximal sediment cores around several sectors of Antarctica indicate strong sea surface warming and ice shelf and sea ice retreat. Benthic deep-sea-core delta (super 18) O values at this time are some of the lowest of the Pleistocene, indicating both deep sea warming and reduced global ice volume. A coeval alignment of orbital parameters produces one of the strongest high-latitude summer insolation anomalies of the last several million years. Here we use a 3-D ice sheet-shelf model to simulate the evolution of Antarctic ice sheets through the event, and a global climate model to simulate temperatures and sea ice during peak Antarctic warmth. The ice model predicts nearly complete collapse and subsequent recovery of marine ice in West Antarctica, and the ice and climate model results agree well with proximal sediment core data in the Ross Embayment recovered by the ANDRILL and Cape Roberts drilling projects. The dominant forcing is found to be variations in sub-ice-shelf oceanic melting, with insignificant surface melting of terrestrial ice flanks even during peak warmth. Implications are noted in light of other observations and theories of Pliocene-Pleistocene Antarctic ice sheet variability that do involve surface melt. Abstract Copyright (2012) Elsevier, B.V.