[M-IS15] 南大洋・南極氷床が駆動する全球気候変動

[MIS15-06] Cross-check of dust-magnetic correlation and oxygen isotope stratigraphy in the Southern Ocean

*松井 浩紀¹、池原 実¹、菅沼 悠介^2,3、関 宰⁴、奥野 淳一^2,3、大藪 幾美²、川村 賢二^2,3 (1.高知大学海洋コア総合研究センター、2.国立極地研究所、3.総合研究大学院大学 複合科学研究科極域科学専攻、4.北海道大学低温科学研究所)

キーワード：南大洋、年代学、酸素同位体比層序、風成塵-磁気記録対比

Southern Ocean (SO) marine core chronology forms the basis of understanding the past SO climates. Since the traditional oxygen isotope stratigraphy has difficulty in the SO due to general lack of calcareous foraminifera, dust-magnetic correlation is a promising way for chronology. However, the reliability of the circum-Antarctic dust-magnetic correlation was not fully confirmed, even beyond the last 100 kyrs. Here we show dust-magnetic correlation coupled to oxygen isotope stratigraphy at the marine core in the Indian sector of the SO, and compile the available sites in the Atlantic and Pacific sectors of the SO in order to validate the dust-magnetic correlation. The oxygen isotope stratigraphy confirmed that dust-magnetic correlation is applicable in the SO at least through the last 450 kyrs but revealed non-negligible difference between the two age models. The dust age models tended to be a few thousand kyrs older than the oxygen isotope stratigraphy especially at the glacial terminations. We conducted the phase analysis to show that sedimentation process cannot fully account for the observed difference between the two age models. We then compared, based on dust age models, SO oxygen isotope records with the global benthic stack curve and found that SO oxygen isotope changes earlier than the stack curve. Thus, the early rise in SO bottom water temperature and late response of ice sheet volume would be responsible for the differences between the two age models.