HR: 14:55h
AN: PP13B-06    [Abstracts]
TI: Sea-surface and deep-sea temperatures and seawater d18O in the Southern Ocean over the last 440,000 years
AU: * Tripati, A
EM: atri02@esc.cam.ac.uk
AF: Earth Sciences, University of Cambridge Downing Street, Cambridge, CB2 3EQ United Kingdom
AU: Greaves, M
EM: mg109@esc.cam.ac.uk
AF: Earth Sciences, University of Cambridge Downing Street, Cambridge, CB2 3EQ United Kingdom
AU: Elderfield, H
EM: he101@esc.cam.ac.uk
AF: Earth Sciences, University of Cambridge Downing Street, Cambridge, CB2 3EQ United Kingdom
AU: Hall, I
EM: n/a
AF: Earth Sciences, University of Cardiff, Wales, XXXXX United Kingdom
AU: Barker, S
EM: n/a
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 00000 United States
AB: The circulation of Antarctic Bottom Water is one of the controlling factors in the Earth's heat budget, and therefore Southern Ocean paleoceanography is critical to understanding glacial-interglacial climate change. Ocean Drilling Program (ODP) Site 1123 (3290 m water depth) on Chatham Rise (41ø 47.15' S, 171ø 28.94' W) is located just north of the present-day Subtropical Convergence, below the Pacific Deep Western Boundary Current, within the depth range of Antarctic Bottom Water. The recovered sedimentary sequence from ODP Site 1123 contains a record of Southern Ocea, hydrographic variations over several glacial-interglacial cycles: We present a 440,000 year record of surface and deepwater hydrographic variability based measurements of Mg/Ca and stable isotope ratios in planktic and benthic foraminifera. Planktic Mg/Ca-based temperatures indicate a maximum glacial-interglacial temp. change of 7.5øC. The planktic record shares many features in common with a record from a shallower site located just south of the Subtropical Convergence excepth that temp. changes across Termin. 1 and 2 aren't seen at Site 1123. Possible reasons for this include hydrographic differences between sites, foraminiferal habitat, and dissolution artifacts. Glacial-interglacial benthic Mg/Ca differences are variable through the record, with coldest temperatures inferred for Stages 8 and 10. Deep-water temps. based on Mg/Ca indicate LGM values of -0.8øC (calibration of Martin et al. 2002) and a seawater d18O of 1.0 per mil (VSMOW), similar to the porewater-based reconstruction at this site (Adkins et al. 2002).
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting