Reconciling glacial Antarctic water stable isotopes with ice sheet topography and the isotopic paleothermometer

Climate-related variabilities in the Styx-M ice core record from northern Victoria Land, East Antarctica, during 1979-2014

The historical climate variability in East Antarctica inferred from ice cores remains under debate owing to the vastness and complexity of the region. This study evaluates the potential climate variabilities in the Styx-M ice core records (δ18O, d-excess, and snow accumulation) from northern Victoria Land adjacent to the Ross Sea sector of East Antarctica during 1979-2014. Results show that the primary moisture source in this area is the Pacific Ocean sector. Although the annual mean δ18O values was limited to directly indicate the temperature changes, a weak relevance between the average δ18O values and the temperature signal during the austral summer season is detectable. δ18O, d-excess, and snow accumulation correlate with sea surface temperature and sea ice extent in the Ross Sea sector. A coupled influence of the SAM, ASL, and ENSO climate indices is expected, because the oceanic environment in this region is influenced by them. The pronounced intrusion of oceanic moisture coupled with atmospheric circulation patterns over the Ross Sea region makes the Styx-M ice core a promising record of the local oceanic conditions, with the snow accumulation rate being a direct proxy. Additionally, the analysis of trace elements from 1979 to 1999 revealed the presence of crustal dust sourced from the Transantarctic Mountains, as well as non-crustal sources, both intricately linked with atmospheric transport. These results demonstrate that the contributions of-and variations in-oceanic conditions associated with atmospheric circulation changes are detectable and dominant in the Styx-M ice core. This study serves as a basis for interpreting longer parts of the Styx-M ice core.

Multiple episodes of ice loss from the Wilkes Subglacial Basin during the Last Interglacial

The Last Interglacial (LIG: 130,000-115,000 years ago) was a period of warmer global mean temperatures and higher and more variable sea levels than the Holocene (11,700-0 years ago). Therefore, a better understanding of Antarctic ice-sheet dynamics during this interval would provide valuable insights for projecting sea-level change in future warming scenarios. Here we present a high-resolution record constraining ice-sheet changes in the Wilkes Subglacial Basin (WSB) of East Antarctica during the LIG, based on analysis of sediment provenance and an ice melt proxy in a marine sediment core retrieved from the Wilkes Land margin. Our sedimentary records, together with existing ice-core records, reveal dynamic fluctuations of the ice sheet in the WSB, with thinning, melting, and potentially retreat leading to ice loss during both early and late stages of the LIG. We suggest that such changes along the East Antarctic Ice Sheet margin may have contributed to fluctuating global sea levels during the LIG.

Wilkes subglacial basin ice sheet response to Southern Ocean warming during late Pleistocene interglacials

The response of the East Antarctic Ice Sheet to past intervals of oceanic and atmospheric warming is still not well constrained but is critical for understanding both past and future sea-level change. Furthermore, the ice sheet in the Wilkes Subglacial Basin appears to have undergone thinning and ice discharge events during recent decades. Here we combine glaciological evidence on ice sheet elevation from the TALDICE ice core with offshore sedimentological records and ice sheet modelling experiments to reconstruct the ice dynamics in the Wilkes Subglacial Basin over the past 350,000 years. Our results indicate that the Wilkes Subglacial Basin experienced an extensive retreat 330,000 years ago and a more limited retreat 125,000 years ago. These changes coincide with warmer Southern Ocean temperatures and elevated global mean sea level during those interglacial periods, confirming the sensitivity of the Wilkes Subglacial Basin ice sheet to ocean warming and its potential role in sea-level change.

Antarctic surface temperature and elevation during the Last Glacial Maximum

Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations.