HR: 0800h
AN: PP51F-1373    [Abstracts]
TI: Surface and Thermocline Variability of the Eastern Equatorial Pacific During the Last 80,000 yr: Results from ODP Site 1240
AU: * Cacho, I
EM: icacho@ub.edu
AF: GRC Geociencies Marines, Universitat de Barcelona, C/Marti Franques s/n, Barcelona, 08028 Spain
AU: Pena, L D
EM: lpena@ub.edu
AF: GRC Geociencies Marines, Universitat de Barcelona, C/Marti Franques s/n, Barcelona, 08028 Spain
AU: Ferretti, P
EM: patrizia00@esc.cam.ac.uk
AF: Godwin Laboratory, University of Cambridge, Pembroke Street, Cambridge, CB2 3SA United Kingdom
AU: Shackleton, N
EM: njs5@esc.cam.ac.uk
AF: Godwin Laboratory, University of Cambridge, Pembroke Street, Cambridge, CB2 3SA United Kingdom
AB: Recent hypothesis consider low latitudes as the source region for past global rapid climatic changes. In this sense, the Eastern Equatorial Pacific (EEP) is an area with great potential to trigger global changes due to its active role in the El Ni¤o-Southern Oscillation (ENSO). Here we present results obtained from ODP 1240 (Leg 202, 0§ 01.31'N, 86§ 27.76'W, 2921 mbsl) on paired stable isotopes (d18O, d13C) and trace elements (Mg/Ca) on 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 80 kyr, including the entire last glacial period, the glacial-interglacial transition and the Holocene. Chronostratigraphy is currently in progress, but initial results evidence strong changes in sedimentary rates. Higher accumulation rates are recorded during the glacial time and deglaciation, likely reflecting changes in the intensity of the upwelling system (cold tongue expansion). In general, sedimentation rates are relatively high for the region (8-15 cm/kyr) which makes Site 1240 particularly valuable for the study of rapid climatic variability. Results are still preliminary but several rapid oscillations of about 1-2C are observed during MIS 3 in both, SST (G. ruber) and DTT (N. dutertrei) records. Thermocline structure also changed in relation to these oscillations. Last deglaciation is seen as a SST (G. ruber) warming of about 4§C, while lower DTTs (N. dutertrei) increase only about 2§C. This early warming preceded the isotopic depletion of the last deglaciation. A middle deglaciation abrupt cooling event of about 3§C (SST) and 1§C (DTT) interrupted the gradual warming and nearly returning to full glacial conditions. During the Holocene two main periods are easily distinguishable in both d18O and Mg/Ca records. Early Holocene is characterized by higher Mg/Ca and relatively high d18O values whereas Late Holocene presents lower Mg/Ca and lower d18O levels.
DE: 4267 Paleoceanography
DE: 1065 Trace elements (3670)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting