HR: 0800h
AN: C21B-1087    [Abstracts]
TI: Rapid fluctuations of West Antarctic Ice Sheet during the last deglaciation recorded in the sediment cores from off the Antarctic Peninsula
AU: * Yokoyama, Y
EM: yokoyama@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, SciBldg#1, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: * Yokoyama, Y
EM: yokoyama@eps.s.u-tokyo.ac.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, 237-0061 Japan
AU: Noumi, M
EM: masahiro.n@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, University of Tokyo, SciBldg#1, 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Miura, H
EM: miura@nipr.ac.jp
AF: National Institute of Polar Research, 1 chome Kaga, Itabashi, Tokyo, 173-8515 Japan
AU: Ohkouchi, N
EM: nohkouchi@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, 237-0061 Japan
AU: Matsuzaki, H
EM: hmatsu@malt.rcnst.u-tokyo.ac.jp
AF: Research Center for Nuclear Sciecne and Technology, University of Tokyo, 2-11-16 Yayoi, Tokyo, 113-0032 Japan
AB: Far-field sea-level observations and glacio-hydro-isostatic analyses have indicated that considerable amount of ice was stored in Antarctica during the Last Glacial Maximum (LGM), and has been melted during the last 20 ka (Nakada and Lambeck, 1989; Yokoyama et al., 2001). Particular interest for our study is to reveal behavior of the ice sheet during the 2 major rapid ice melting events during the last deglaciation. One is the post-LGM MWP (Melt Water Pulse) at 19 ka (Yokoyama et al., 2000: Clark et al., 2004) and the other is the MWP1a event (Fairbanks, 1989; Bard et al., 1990). Recent observations and modeling results show that Antarctic ice sheet was melted during the MWP1a (Clark et al., 1995; Bassett, et al., 2005) yet the timing and magnitude of waxing and waning of the Antarctic Ice Sheet is still under debate. Direct evidence of ice melting events in the past could be preserved in the sediment cores as the peaks of the IRD (ice rafted detritus) and we have investigated 11 deep sea cores retrieved around the Antarctic Peninsula. Sediment composition reflects their origin and core top radiocarbon results further confirm the source of the icebergs. Radiocarbon dating on sediments together with the assemblage of radiolaria was used to reconstruct the chronology in the cores. We detected 2 major peaks of the IRD respectively at LGM and about 14 ka among the cores. The first peak is corresponding to the expansion of the ice margin around the Antarctic Peninsula during the LGM whereas the latter may be corresponding to the timing of the MWP1a. Considering our results as well as other previous studies suggested that the Antarctic ice sheet, at least in this region, contributed the rapid rise in global sea-level known as MWP1a.
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4219 Continental shelf and slope processes (3002)
DE: 4556 Sea level: variations and mean (1222, 1225, 1641)
DE: 9310 Antarctica (4207)
SC: Cryosphere [C]
MN: Fall Meeting 2005