Mid-Brunhes Transition caused by Antarctic ice sheet melting during MIS11c

Interglacial intensity in past 800 kyr is characterized by a transition, about 430 kyr ago, between the older ones, which were relatively cool and low sea level, and the more recent ones, which were relatively warm and high sea level. This transition, as identified in Antarctic ice core and benthic calcite d¹⁸Oc records, corresponds to the so-called mid-Brunhes Transition (MBT). However, its origin and underlying dynamics remain elusive. Here we show, based on a start-of-art, stable water isotope enabled climate model, that additional ice volume to the present-day levels should be considered in order to reproduce the systematic enrichment in interglacial d¹⁸Oc before the MBT. This extra ice of ~18 e.s.l.m. likely exists in the Antarctic, which in turn weakens vertical mixing in Southern Ocean, potentially accounting for the low interglacial atmospheric CO₂ levels prior to the MBT. Our results further indicate that during MIS11c the unique climate background leads to extra Antarctic ice sheet melting, eventually giving rise to a systematic change in interglacial climate and hence accounting for the MBT.