The file contains Southern Hemisphere winter (September) sea ice concentration (sic) from a simulation performed using the isotope-enabled HadCM3 climate model forced with early last interglacial boundary conditions, centred approximately 128,000 years ago. The resulting sic represents a reduction in winter sea ice area of approximately 54% relative to pre-industrial and is proposed as the best explanation for the Antarctic ice core data from 128,000 years ago. The spatial pattern of sea ice retreat was determined using a large ensemble of model experiments and a pattern search optimization approach to match the last interglacial ice core isotope peak. Further details can be found in the published manuscript (https://doi.org/10.1002/2017GL074594). This work was funded by NERC grants NE/P009271/1, NE/P013279/1, and NE/K004514/1.

The text file (.csv) contains d18O changes simulated at six Greenland deep ice cores (NEEM, NGRIP, GRIP, GISP2, Camp Century and DYE3) from 69 simulations performed using the isotope-enabled HadCM3 climate model forced with mid last interglacial boundary conditions, centred at 125,000 years ago. HadCM3 is used to reproduce the d18O response to 69 modified Last Interglacial (LIG) Greenland Ice Sheet (GIS) morphologies at the ice-core sites. To parameterise the set of 69 GIS morphologies, we undertake a Principal Component Analysis (PCA) approach. The text file also contains the 8PC coefficients for each of the 69 morphologies. The netcdf file (.nc) contains the 8PC shapes and the average shape. To obtain any of the 69 GIS morphologies: (1) store the 8 PC coefficients of a specific GIS morphology and, (2) take a linear combination of the PC shapes (according to those coefficients) and add the average shape. Funding was provided by the following grants: EPSRC-funded Past Earth Network (Grant number EP/M008363/1); NERC funding through grants NE/P009271/1, NE/P013279/1, NE/J004804/1, and Irene Malmierca''s PhD studentship.