HR: 14:00h
AN: PP53B-02 INVITED    [Abstracts]
TI: Rapid increase in global ice volume at the inception of the Last Glacial Maximum
AU: * Yokoyama, Y
EM: yokoyama@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Sciences, University of Tokyo, 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, 2-15 Natsushima, Yokosuka, 237-0061, Japan
AU: Naruse, T
EM: tatsuhiro.n@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Sciences, University of Tokyo, 7-3-1 Hongo, Tokyo, 113- 0033, Japan
AU: Ohkouchi, N
EM: nohkouchi@jamstec.go.jp
AF: Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, 237-0061, Japan
AU: Esat, T M
EM: tze@ansto.gov.au
AF: Institute for Environmental Research, Australian Nuclear Science and Technology Organization, New Illawarra Road, Lucas Heights, NSW, 2234, Australia
AU: Lambeck, K
EM: kurt.lambeck@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Milles Road, Canberra, 0200, Australia
AB: The timing and magnitude of global ice volume changes during the transition between Marine Isotope Stage (MIS) 3 to 2 (ie. LGM) is poorly constrained as relevant sea-level indicators are presently located underwater. Drill cores from buried coral terraces, dated by U-series nuclides, have provided some data, however, additional data are required to reconstruct a reliable global ice volume history for this period. Japan Sea is separated from the open ocean by shallow sills (water depth ranges from 15-135m) and its hydrology is affected by global sea-level changes. We obtained twenty AMS (Accelerator Mass Spectrometry) radiocarbon dates, 2 tephra layer chronologies, and planktonic foraminifera d18O stratigraphy for the last 50,000 years from a sediment core recovered from Oki ridge. Radiocarbon ages of the tephra layers indicate that the Japan Sea reservoir ages for the Holocene and the last glacial period were similar. Organic carbon and nitrogen isotopes were measured throughout the core with a temporal resolution as good as ca. 200 years. Carbon and nitrogen isotope ratios during the Holocene remained remarkably constant and the shift from the LGM towards the Holocene occurred at ca. 19 cal ka. Carbon isotopes during the LGM were also stable and the transition from 2 per mil heavier carbon to LGM values was evident at about 28 cal ka. A similar shift is present in the nitrogen isotopes and points to major environmental changes at this time. We have also measured oxygen isotopes in planktonic forams which show a freshening in the salinity of the Japan Sea, compared to present, during periods of low sea-level. The timing of the changes in d18O also correspond to the shifts in the C and N isotopes. Therefore, it is reasonable to assume that the cause of the observed environmental changes in the Japan Sea can be attributed directly to the rapid fall in sea-level from MIS-3 to the LGM. Our records, combined with global sea-level data, suggest that the LGM started at about 30 ka with almost 50m fall in sea-level in 2000 years. The timing and magnitude of the LGM inception is consistent with coral records from Huon Peninsula and Barbados.
DE: 0726 Ice sheets
DE: 1222 Ocean monitoring with geodetic techniques (1225, 1641, 3010, 4532, 4556, 4560, 6959)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1621 Cryospheric change (0776)
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting