Response of the Wilkes Subglacial Basin Ice Sheet to Southern Ocean Warming During Late Pleistocene Interglacials

The growth and decay of marine ice sheets act as important controls on regional and global climate and sea level. The Wilkes Subglacial Basin ice sheet appears to have undergone thinning and ice discharge events during recent decades, but its past dynamics are still under debate. The aim of our study is to investigate ice margin retreat of the Wilkes Subglacial Basin ice sheet during late Pleistocene interglacials with the help of new high-resolution records from the TALDICE ice core. Here we present a multiproxy approach associated with modelling sensitivity experiments.

The novel high-resolution δ¹⁸O signal reveals that interglacial periods MIS 7.5 and 9.3 are characterized by a unique double-peak feature, previously observed for MIS 5.5 (Masson-Delmotte et al., 2011), that is not seen in other Antarctic ice cores. A comparison with our GRISLI modelling results indicates that the Talos Dome site has probably undergone elevation variations of 100-400 m during past interglacials, with a major ice thickness variation during MIS 9.3, likely connected to a relevant margin retreat of the Wilkes Subglacial Basin ice sheet. To validate this elevation change hypothesis, the modelling outputs are compared to the ice-rafted debris record (IBRD) and the neodymium isotope signal from the U1361A sediment core (Wilson et al., 2018), which show that during MIS 5.5 and especially MIS 9.3, the Wilkes Subglacial Basin ice sheet has been subjected to ice discharge events.

Overall, our results indicate that the interglacial double-peak δ¹⁸O signal could reflect decreases in Talos Dome site elevation during the late stages of interglacials due to Wilkes Subglacial Basin retreat events. These changes coincided with warmer Southern Ocean temperatures and elevated global mean sea level, confirming the sensitivity of the Wilkes Subglacial Basin ice sheet to ocean warming and its potential role in sea-level change.