2:30 PM - 2:45 PM
[MIS10-15] Pliocene Western Antarctic Ice History: Diatoms at Site U1532 in Amundsen Sea and its implications
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.
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.