HR: 0800h
AN: OS31B-1443    [Abstracts]
TI: Multi-Proxy Approach to the Atlantic-Indian Water Interchange Along the Last Three Glacial-Interglacial Cycles
AU: * Martínez Méndez, G
EM: gema.martinez@uab.es
AF: Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Edifici Cn, Campus Bellaterra, Cerdanyola, E-08193 Spain
AU: Zahn, R
EM: rainer.zahn@uab.es
AF: Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Edifici Cn, Campus Bellaterra, Cerdanyola, E-08193 Spain
AU: Zahn, R
EM: rainer.zahn@uab.es
AF: Instituciò Catalana de Recerca i Estudis Avancats i Institut de Ciència i Tecnologia Ambientals, Edific Cn, Campus Bellaterra, Cerdanyola, E-08193 Spain
AU: Hall, I
EM: Hall@cardiff.ac.uk
AF: School of Earth, Oceans and Planetary Sciences, Cardiff University, Park Place, Cardiff, CF10 3YE United Kingdom
AU: Rickaby, R
EM: Rosalind.Rickaby@earth.ox.ac.uk
AF: Department of Earth Sciences, Oxford University, Parks Road, Oxford, OX1 3PR United Kingdom
AB: Multi-centennial mean grainsize (SS), paired planktonic ( G. bulloides) and benthic foraminifera ( C. wuellerstorfi ) stable isotope and trace element records of IMAGES core MD96-2080 are used to document surface and deep interchange of waters between the Atlantic and Indian oceans. The core is from the western slope of the Agulhas Bank, off the southern tip of Africa, within the main gateway of Atlantic-Indian ocean interbasin exchange. At a water depth of 2488 m it is currently located within the southern extension of NADW bounded above and below by Upper and Lower CDW. The records display prominent orbital modulation and faster sub-orbital variability that is linked to climate variability seen in marine records at high southern latitudes, and in Antarctic ice core records. Departures from the orbitally modulated pattern occur in benthic C-13 along MIS 5 suggesting an alternation between water masses with similar C-13 signature. Low C-13 levels during glacial periods point to a substitution of NADW by CDW, while flow speeds are increased as indicated by high values of SS. The pattern mimics that seen at a mid-depth SW Pacific core site (Hall et al., 2001) suggesting a hemisphere-wide significance for the southern hemisphere oceans. The combined benthic C-13 and Cd/Ca patterns are used to discriminate between water masses and to separate preformed from THC-related signals contained in the glacial-interglacial and millennial patterns. The data profiles show significant differences in the rate of change of ice volume (O-18), chemical ventilation (C-13) and physical circulation (SS) during glacial to interglacial transitions and interglacial to glacial transitions that suggest a large inertia of ocean physics but also confirm the significance of Southern Ocean THC water mass formation for changing deep ocean ventilation. Coherency between the planktonic and benthic isotope records points to the existence of a direct connection between Agulhas leakage and deep outflow from the South Atlantic. The paleotemperature and paleonutrient records provide a valuable tool to assess Agulhas leakage and its linking with the vigour of MOC.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4924 Geochemical tracers
DE: 4962 Thermohaline
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005