Refining Estimates of Polar Ice Volumes during the MIS11 Interglacial Using Sea Level Records from South Africa

Peak eustatic sea level (ESL), or minimum ice volume, during the protracted marine isotope stage 11 (MIS11) interglacial at similar to 420 ka remains a matter of contention. A recent study of high-stand markers of MIS11 age from the tectonically stable southern coast of South Africa estimated a peak ESL of 13 m. The present study refines this estimate by taking into account both the uncertainty in the correction for glacial isostatic adjustment (GIA) and the geographic variability of sea level change following polar ice sheet collapse. In regard to the latter, the authors demonstrate, using gravitationally self-consistent numerical predictions of postglacial sea level change, that rapid melting from any of the three major polar ice sheets (West Antarctic, Greenland, or East Antarctic) will lead to a local sea level rise in southern South Africa that is 15%-20% higher than the eustatic sea level rise associated with the ice sheet collapse. Taking this amplification and a range of possible GIA corrections into account and assuming that the tectonic correction applied in the earlier study is correct, the authors revise downward the estimate of peak ESL during MIS11 to 8-11.5m.