HR: 1330h
AN: PP22A-1203    [PDF]
TI: Orbital-scale El Ni\~{n}o/Southern Oscillation-Like Variability During the Last Glacial-Interglacial Cycle
AU: * Yamamoto, M
EM: myama@ees.hokudai.ac.jp
AF: Graduate School of Environmental Earth Science, Hokkaido University, Kita-10, Nishi-5, Kita-ku, Sapporo, 060-0810 Japan
AU: Oba, T
EM: oba-tad@ees.hokudai.ac.jp
AF: Graduate School of Environmental Earth Science, Hokkaido University, Kita-10, Nishi-5, Kita-ku, Sapporo, 060-0810 Japan
AU: Shimamune, J
AF: Graduate School of Environmental Earth Science, Hokkaido University, Kita-10, Nishi-5, Kita-ku, Sapporo, 060-0810 Japan
AU: Ueshima, T
EM: ueshima@ees.hokudai.ac.jp
AF: Graduate School of Environmental Earth Science, Hokkaido University, Kita-10, Nishi-5, Kita-ku, Sapporo, 060-0810 Japan
AB: How have the changes in the Earth's orbit have driven glacial-interglacial climate changes? Recently, a new hypothesis has been proposed that the tropical Pacific ocean-atmosphere interactions have a strong influence on global climate changes on an orbital timescale (Cane, 1998; Clement et al., 1999; Lea et al., 2000). Nevertheless, the orbital-scale changes in the tropical interactions are less clear, and their impacts on a global climate have not yet been proven. Our study was aimed at understanding whether or not and how the long-term tropical El Ni\~{n}o-Southern Oscillation (ENSO)-like variability has a global impact on orbital-scale climate changes. We generated continuous records of the alkenone sea surface temperature (SST) at the western and eastern margins of the mid-latitude North Pacific (MD012421 and ODP1014) during the last 145,000 years. We found that the difference between the SSTs of the NE and NW Pacific margins ($\Delta$SST) reflected an orbital-controlled ENSO-like variability, and the $\Delta$SST can be used as an indication of the long-term ENSO. The variation of $\Delta$SST was large and pronounced at the 23-kyr cycle during 0-60 ka (MIS-1 to MIS-3) and 120-145 ka (MIS-5e to MIS-6), which agreed well with the long-term ENSO behavior predicted by the Zebiak-Cane ENSO model (Clement et al., 1999), as regards both the timing and frequency. In contrast, the variation was relatively small and pronounced at the 41-kyr cycle during 60-120 ka (MIS-4 to MIS-5d), which disagreed with the model prediction. Our observation also demonstrated that a strongly El Ni\~{n}o-like SST pattern prevailed in the mid-latitude North Pacific during the last two deglaciations. The synchronous warming of the Antarctica (Petit et al., 1999) and the tropical Pacific (Lea, 2000; Koutavas et al., 2002; Visser et al., 2003) prevailed within these strongly El Ni\~{n}o-like intervals during deglaciations. These findings are concordant with Cane (1998)'s hypothesis that a long-term El Ni\~{n}o must have resulted in global heating. Both meridional heat transport and pCO$_{2}$ increases might have been accelerated under a strongly El Ni\~{n}o-like condition during the last two deglaciations. These new findings suggest that a strongly El Ni\~{n}o-like condition was essential to the global warming that induced glacial terminations.
DE: 1055 Organic geochemistry
DE: 1620 Climate dynamics (3309)
DE: 4516 Eastern boundary currents
DE: 4522 El Ni¤o
DE: 4576 Western boundary currents
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting