Transition of Glacial Regimes Recorded at IODP Site U1524 in the Ross Sea, Antarctica, Over the Last 800 Thousand Years

Abstract

Reconstructing past interactions between the West Antarctic Ice Sheet (WAIS) and changing environmental conditions in the Ross Sea region can help determine long‐term WAIS stability. Existing sedimentary records reveal changes to oceanography, sea ice and ice sheet extent over the glacial‐interglacial cycles of the last ∼800 kyr. There are, however, few high‐resolution, ice‐proximal records extending to before the Last Glacial Maximum. Here, we examine a broad suite of lithological, biogenic, physical property and geochemical data from International Ocean Discovery Program (IODP) Site U1524 from the continental rise in the central Ross Sea. An age model spanning the last ∼800 kyr is established within constraints provided by biostratigraphy, palaeomagnetism and foraminifera amino acid racemization. Lithofacies analysis reveals the pattern of glacial advance and interglacial retreat. Enhanced delivery of ice rafted debris and preservation of radiolaria occurs during deglacial and interglacial periods, with fine‐grained diatom‐bearing to diatom‐rich sediments deposited during glacial periods. Foraminifera are preserved during the latest parts of the Marine Isotope Stage (MIS) 11 and 9 interglacials. Proxy data apparently suggest higher productivity during glacial periods, which is explained by reworking and redeposition of older detritus from the continental shelf. A change in the character of glacial period sediments after MIS 7 (∼200 kyr ago) suggests there was a less extensive grounded ice sheet during the last two glacial periods. Together, these results provide a detailed reconstruction of mid‐ to late‐Pleistocene ocean–ice sheet interactions, improving understanding of how the Ross Sea region may respond to ongoing climate change.