Japan Geoscience Union Meeting 2024

Presentation information

[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS10] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

Fri. May 31, 2024 1:45 PM - 3:00 PM 105 (International Conference Hall, Makuhari Messe)

convener:Kazuya Kusahara(Japan Agency for Marine-Earth Science and Technology), Takeshige Ishiwa(National Institute of Polar Research), Ikumi Oyabu(National Institute of Polar Research, Research Organization of Information and Systems), Osamu Seki(Institute of Low Temperature Science, Hokkaido University), Chairperson:Kazuya Kusahara(Japan Agency for Marine-Earth Science and Technology), Takeshige Ishiwa(National Institute of Polar Research), Ikumi Oyabu(National Institute of Polar Research, Research Organization of Information and Systems), Osamu Seki(Institute of Low Temperature Science, Hokkaido University)


2:30 PM - 2:45 PM

[MIS10-15] Pliocene Western Antarctic Ice History: Diatoms at Site U1532 in Amundsen Sea and its implications

*Masao IWAI1, Keiji Horikawa2 (1.Marine Core Research Institute, Kochi University, 2.Toyama University)

Keywords:Warm Pliocene, Amundsen Sea, diatom, Western Antarctic Ice Sheet

The West Antarctic Ice Sheet along the Amundsen Sea is most sensitive against modern warming and remarkable decreasing has been observed, and it has been pointed out that WAIS may have collapsed many times in the past (Gohl et al., 2019). We have investigated fossil diatoms in samples taken from Pliocene section at the IODP Site 379-U1532 (3962m water depth) on the continental drift, where the estimated linear sedimentation rates up to 20-60 cm/k.y., higher than any other previous drilled sites, to assess details of a highly dynamic WAIS during the warm Pliocene.
A total of 528 processed slides were examined for a quantitative diatom analysis, with sampling intervals up to every 5cm for biosiliceous sediments. Diatoms were detected from 489 samples and recognized more than 120 taxa with 49 Genera.
Our detail analysis suggests that the diatom abundance peak of MIS Gi1 near the Gauss-Gilbert boundary (3.596Ma, GMT2020) were more clear and higher than that of Wilkes Land site (Armbrecht et al., 2018). Careful correlation suggests that WAIS had been collapsed slightly earlier than EAIS, at least in this horizon. In addition, reworked diatom that assemblages are slightly different within each greenish interval suggest it is a potential indicator to show how WAIS was retreated.
Comparing to the modern diatom ecological information (Armand et al., 2005; Crosta et al., 2005), summer SST during Pliocene interglacial was mild (1-5 deg-C) during 3.4-3.7Ma, warmer (up to 5 deg-C) at 3.9Ma and 4.3Ma, and colder (~1 deg-C) during 4.5-4.7Ma. Reworked diatom assemblage profile suggest, that the WAIS was retreeted rather than modern ice sheet during the warmer Pliocene during 3.4-3.7Ma.