2026-02-04 ヒューストン大学（UH)
＜関連情報＞
- https://www.uh.edu/news-events/stories/2026/february/02042026-researcher-collects-ancient-antarctic-sediment.php
- https://www.pnas.org/doi/10.1073/pnas.2508341122
鮮新世におけるスワイツ氷河とパイン島氷河（西南極）の内陸部への大規模な後退の繰り返し Repeated major inland retreat of Thwaites and Pine Island glaciers (West Antarctica) during the Pliocene
Keiji Horikawa, Masao Iwai, Claus-Dieter Hillenbrand, +10 , and Expedition 379 Science Party
Proceedings of the National academy of Sciences Published:December 22, 2025
DOI:https://doi.org/10.1073/pnas.2508341122
Significance
Significant melting of the Thwaites and Pine Island glaciers in the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) threatens its stability. The WAIS state during the Pliocene, a period mirroring potential future climate warming, provides key insights into its behavior under a warmer climate. To constrain the Pliocene state of the WAIS, we analyzed geochemical provenance data on a sediment core located off the Amundsen Sea Embayment. Our reconstruction of the Pliocene configuration of the Amundsen Sea sector reveals repeated, major ice-sheet retreat events, demonstrating the WAIS’s vulnerability to warm conditions. Our findings highlight the risk of partial or even complete collapse of the WAIS under current global warming, which would cause meter-scale global sea-level rise.
Abstract
The stability of the West Antarctic Ice Sheet (WAIS), crucial for predicting future sea-level rise, is threatened by ocean-forced melting in the Pacific sector of the Southern Ocean. While some geological records and ice-sheet models suggest WAIS retreat during past warm periods, reliable data constraining the extent of retreat are lacking. Detrital Nd, Sr, and Pb isotope data of sediments recently drilled at International Ocean Discovery Program (IODP) Site U1532 on the Amundsen Sea continental rise manifest repeated alternations in sediment provenance during glacial–interglacial cycles of the Pliocene (5.33 to 2.58 Mya), a time warmer than present. The variations reflect large fluctuations in WAIS extent on the Antarctic continent. A unique high Pb/low εNd signature of sediments found at the onset of glacial intervals (3.88, 3.6, and 3.33 Ma) is attributed to the supply of detritus sourced from plutonic rocks located in the West Antarctic interior. Its isotopic signature at Site U1532 indicates major inland retreat of the WAIS during the preceding interglacials. During peak interglacials, the ice margin had retreated inland, and icebergs rafted and deposited inland-sourced detritus over 500 km across the Amundsen Sea shelf. Subsequent readvance of grounded ice then “bulldozed” these inland-derived fine-grained sediments from the shelf down to the continental slope and rise, resulting in a high Pb/low εNd peak in the rise sediments. Our continuous Pliocene records provide conclusive evidence for at least five major inland retreat events of the WAIS, highlighting the significant vulnerability of the WAIS to ongoing warming.
