The Spatial Structure of the 128 ka Antarctic Sea Ice Minimum

We compare multi-ice core data with δ¹⁸O model output for the early last interglacial Antarctic sea ice minimum. The spatial pattern of δ¹⁸O across Antarctica is sensitive to the spatial pattern of sea ice retreat. Local sea ice retreat increases the proportion of winter precipitation, depleting δ¹⁸O at ice core sites. However, retreat also enriches δ¹⁸O because of the reduced source-to-site distance for atmospheric vapor. The joint overall effect is for δ¹⁸O to increase as sea ice is reduced. Our data-model comparison indicates a winter sea ice retreat of 67, 59, and 43% relative to preindustrial in the Atlantic, Indian, and Pacific sectors of the Southern Ocean. A compilation of Southern Ocean sea ice proxy data provides weak support for this reconstruction. However, most published marine core sites are located too far north of the 128,000 years B.P. sea ice edge, preventing independent corroboration for this sea ice reconstruction.