| 其他摘要 | The Western Tropical Pacific plays a critical role in global water vapor and heat transport. Many studies had shown the strong correlation between tropical climate and high latitude climate variability, in particular, the Intertropical Convergence Zone (ITCZ) migration. But there is still little known about how they cooperate with each other. In this work, we studied the top 320cm gravity core at site KX97322-4 (00°01'S, 159°14'E, water depth 2362m) at 2cm steps, which was recovered from the Ontong-Java Plateau in the Western Equatorial Pacific (WEP), the center of the Western Pacific Warm Pool (WPWP), where now the annual average temperature is more than 29℃. The age model is based on the correlation of the planktonic foraminiferal δ18O record with the LR04 reference benthic stack and the last occurrence(~120ka B.P.) of Globigerinoides ruber (pick)[35]. The bottom age could be ~188ka B.P.(MIS 6). By combining planktonic foraminifera G. ruber calcite Mg/Ca and δ18O, we obtained the local Sea Surface Temperature (SST) and Salinity (SSS) over the past 200ka. In general, the WPWP SST swift culminated in deglacial then declined until the next deglacial. During the last two glacial (MIS 2~5d, MIS 6), the Western Tropical Pacific SST cooling could be 3.3℃ and 3.6℃ respectively. During MIS 2~4, the SST was 26~28℃ and got it’s minimum value 25.9℃ in 67.3ka BP. During MIS 6 SST was warming multisteply and attended its maximum value 30.17℃ in MIS 5e. In the Last Glacial Maximum (LGM), the SST minimum value in the center of WPWP was 26.2℃, about 2.9±0.7℃ cooler than now. We use the sea water δ18O (δ18Osw) value minus the global mean δ18Osw to remove the influence from ice volume change to get the local precipitation history. The maximum and the minimum value of the δ18Osw is 1.76‰ and 0.35‰, respectively in the MIS 6 and MIS 5e. By comparing the SST records of WEP with the Eastern Equatorial Pacific (EEP) since MIS 6, we find that the Tropical Pacific was more likely in the phase of El Niño-like during Terminations and warming stage in glacial stage (MIS 6). Meanwhile, more water vapor and heat had been transported to dipolar areas. During the Terminations, when the globe was warming, the zonal gradient of tropical pacific and global ice volume decreased. In the warming stage of MIS 6, the zonal gradient was lower, whereas the global ice volume sustained growth, maybe the heat was not enough to promote the melting of glacier at this moment, but the water vapor transport contributed to the glacier building in polars. Due to numerous factors can influence the salinity change, with the results of the comparation of the δ18Osw between the WEP and EEP, we can not draw out the precipitation difference. By comparing the WEP precipitation records from KX97322-4 and MD05-2920 with Chinese cave stalagmite records, we find that the tropical pacific was bound up with the ITCZ changes and even could influence East Asia Monsoon precipitation. When the isolation became stronger, the globe was warming and the WEP precipitation declined and evaporation enhanced, the ITCZ with more moisture shifted from the near equator to the temperate latitude, then the East Asia precipitation was strengthened. Our finding provide new evidence to the relationship between the WEP sea surface water variation and the East Asia precipitation, the Tropical Pacific zonal variation during the global warming and the ITCZ change during the past 200ka.
|
; 李铁刚
修改评论