Marine Isotope Stage (MIS) 5e (130–116 ka) represents a “laboratory” for evaluating climate model performance under warmer-than-present conditions. Climate model simulations for MIS 5e have previously failed to produce Southern Ocean (SO) sea-surface temperatures (SSTs) and sea-ice extent reconstructed from marine sediment core proxy records. Here we compare state of the art HadGEM3 and HadCM3 simulations of Peak MIS 5e SO summer SSTs and September sea-ice concentrations with the latest marine sediment core proxy data. The model outputs and proxy records show the least consistency in the regions located near the present-day SO gyre boundaries, implying the possibility that model simulations are currently unable to fully realize changes in gyre extent and position during MIS 5e. Including Heinrich 11 meltwater forcing in Peak MIS 5e climate simulations improves the likeness to proxy data but it is clear that longer (3–4 ka) run times are required to fully test the consistency between models and data. © 2023. The Authors.

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