HR: 1330h
AN: PP32A-0277    [PDF]
TI: Temperature changes in tropical oceans over the last 140.000 years based on $\delta$ $^{44}$Ca, Mg/Ca and $\delta$ $^{18}$O: Warming predates melting at glacial-interglacial transitions
AU: * Hippler, D
EM: hippler@geo.unibe.ch
AF: Institute of Geological Sciences, University of Bern Erlachstrasse 9a, Bern, 3012 Switzerland
AU: Mueller, A
EM: amueller@gm.ufz.de
AF: UFZ Environmental Research Centre Halle-Leipzig Ltd, Brueckstr. 3a, Magdeburg, 39114 Germany
AU: Eisenhauer, A
EM: aeisenhauer@geomar.de
AF: Marine Environmental Sciences, GEOMAR Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Naegler, T F
EM: naegler@geo.unibe.ch
AF: Institute of Geological Sciences, University of Bern Erlachstrasse 9a, Bern, 3012 Switzerland
AB: Here we present a refinement of the current $\delta$ $^{44}$Ca-temperature calibration (Naegler et al. 2000) based on modern and fossil planktonic foraminifera {\it Globigerinoides sacculifer} demonstrating the high potential of Ca isotopes as an SST-proxy. Ca isotope measurements performed on modern specimen of {\it G. sacculifer} result in a quantitatively resolvable $\delta$ $^{44}$Ca change per degree Celcius defined by a linear regression. The SST(Mg/Ca)-cross-calibrated thermometer based on fossil {\it G. sacculifer} from sediment core GeoB1112 (tropical East Atlantic) supports the refined calibration in slope and absolute temperatures. The slope of the observed temperature dependence is also identical to the published calibration based on cultured specimen. However, there is an offset of approximately $3.5\deg$C. The refined $\delta$ $^{44}$Ca-thermometer tend to predict lower sea surface temperatures than the published $\delta$ $^{44}$Ca-thermometer. The most probable reason is that cultured samples are biased. Extending a multi-proxy approach, application of this independent method to fossil {\it G. sacculifer} covering the past 140.000 years of sediment core GeoB 1112 from tropical East Atlantic confirms known changes in SST reflecting glacial-interglacial cycles. Pronounced changes of $\delta$ $^{44}$Ca are found at Terminations I (Holocene-LGM) and Termination II (MIS 5e-6). According to the refined temperature calibration the glacial-interglacial amplitude of the record is $3.0-3.5\deg$C for Termination I and slightly higher for Termination II with $4.0-4.5\deg$C, respectively. Interglacial MIS 5e is characterised by a double peak in SST. Both independent proxies ($\delta$ $^{44}$Ca, Mg/Ca) indicate that for both terminations the increase in SST predates ice melting as reflected by the oxygen isotope record by several thousend years. This is in line with previously published data for the Pacific. Additionally we will present first results of tropical temperature changes in the south-western Indo-Pacific Warm Pool. References: Naegler, T. F. et al. (2000) G3, 1, 2000GC000091.
DE: 1040 Isotopic composition/chemistry
DE: 4267 Paleoceanography
DE: 9325 Atlantic Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting