HR: 09:45h
AN: PP21A-06 INVITED     [Abstracts]
TI: Variability in surface and thermocline temperatures of the Eastern Equatorial Pacific during the last glacial period
AU: * Cacho, I
EM: icacho@ub.edu
AF: GRC Geociencies Marines, Universitat de Barcelona, C/Mart¡ Franques s/n, Barcelona, 08024 Spain
AU: Ferretti, P
EM: patrizia00@esc.cam.ac.uk
AF: Godwin Laboratory, University of Cambridge, Pembroke Street, Cambridge, CB2 3SA United Kingdom
AU: Pena, L
EM: lpena@ub.edu
AF: GRC Geociencies Marines, Universitat de Barcelona, C/Mart¡ Franques s/n, Barcelona, 08024 Spain
AU: Shackleton, N
EM: njs5@cam.ac.uk
AF: Godwin Laboratory, University of Cambridge, Pembroke Street, Cambridge, CB2 3SA United Kingdom
AB: Here we present results from ODP Core Site 1240 (Leg 202, 0 ° 01.31'N, 86° 27.76'W, 2921 mbsl) located in the Eastern Equatorial Pacific (EEP), under the northern edge of the so-called "Cold Tongue". This frontal system separates the cold, salty waters of the Peru Current from warmer and fresher tropical waters of the Northern Hemisphere. This study is based on paired stable isotopes (δ¹⁸O, δ¹³C) and trace elements (Mg/Ca) from planktonic foraminifera. Multiple species with different dwelling preferential depths were studied to reconstruct both surface and thermocline characteristics. Core-top Mg/Ca inferred temperatures are in good agreement with current mean annual sea surface temperature (SST) and deep thermocline temperatures (DTT) as recorded from available data from hydrographical stations. Our reconstruction covers the last glacial period at centennial-time resolution. Age model has been constructed in base to eight AMS ¹⁴C dates for the last 20 kyr interval. The older section of Site 1240 has been dated after visual correlation of the δ¹⁸O record measured in the deep thermocline dwelling foraminifer N. dutertrei and the Deuterium record from the Antarctic. The resemblance of both records is very remarkable, as is confirmed by the high correlation coefficient (R=0.92) estimated for the tied interval. Results reveal the occurrence of several rapid oscillations of about 1-2° C are observed during MIS 3 in both, SST (G. ruber) and DTT (N. dutertrei) records. Apparently, most of the Heinrich Events correlate with short warming phases although they are not particularly large within the record. N. dutertrei record indicates a long term shallowing of the thermocline across the glacial period and the occurrence of some millennial events of deepening. These events correlate with intervals of relatively high salinity in the surface layer. These changes are likely to reflect short term oscillations in the ITCZ in relation to high latitude millennial-scale oscillations.
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2005 Joint Assembly