Testing the presence of the climate mode warmer than present based on the paleoenvironmental analysis

在本项目的最后一年，我们对秋田附近的MD-2408岩心进行了最近160个月(27m以上)的烯酮和主元素分析，并对秋田附近的PC-5岩心进行了高分辨率的粒度分析，覆盖了海相同位素阶段5和6。通过结合第二年我们在老脊和秋田附近获得的数据，我们重建了过去160年来烷烃类化合物SST(海表面温度)和风尘尘埃粒度南北梯度的时间变化。结果表明：1)秋田附近PC-5冰芯记录的风尘颗粒大小变化具有明显的千年尺度变化，这与格陵兰冰芯记录的Dansgaard-Oeschger旋回(DOC)的千年尺度变化一致。此外，在MIS5e期间，PC-5岩心的风尘颗粒大小变化也表现出类似于GRIP记录的千年尺度变化。握住d^lt；18&gt；O Recor…MIS5E期间的更多数据因其可能的干扰而一直存在争议。然而，我们新的风尘沙尘粒度记录有力地支持了MIS5E期间GRIP记录的可靠性，并表明在间冰期存在气候突变。2)N-S对近130年风尘沙尘粒度的比较也表明，在北方夏季太阳活动较高的时期夏季风加强。在此基础上叠加了千年尺度的变化和夏季风的加强，这表明千年尺度的气候跃变与夏季风锋的N-S跃变有关。3)5E期间日本海的烷酮SST比现在的千年尺度海温高出约5℃，在对马暖流持续影响的冲之脊，海温的变化不明显，而由于对马暖流的间断影响，海温与DOC表现出明显的千年尺度变化。较少

In the last year of this project, we conducted alkenone and major element analysis of MD-2408 core off Akita covering the last 160 kys (upper 27m), and high-resolution grain size analysis of PC-5 core further off Akita covering the MIS (Marine Isotope Stage) 5 and 6. By combining the data from Old Ridge and off Akita that we obtained in the second year, we reconstructed temporal variations of the north-south gradients of alkenone SST (Sea Surface Temperature) and eolian dust grain size during the last 160 kys. The results are as follows.1) The eolian dust grain size variation during the last 100 kys recorded in PC-5 core off Akita shows distinct millennial-scale variability that faithfully follows the millennial-scale variability of d^<18>O record of Greenland ice (GRIP) core known as Dansgaard-Oeschger Cycles (DOC). In addition, eolian dust grain size variation in PC-5 core shows similar millennial-scale variation during the MIS 5e similar to d^<18>O record of GRIP. GRIP d^<18>O recor … More d during the MIS 5e has been controversial because of its possible disturbance. However, our new eolian dust grain size record strongly support the reliability of the GRIP record during the MIS 5e and suggest the presence of abrupt climatic changes during interglacial periods.2) N-S comparison of the eolian dust grain size during the last 130 kys also suggests intensification of the summer monsoon during the periods of higher northern summer insolation. Superimposed on this are millennial-scale changes with intensified summer monsoon during the interstadials of DOC, suggesting millennial-scale climatic jump is associated with N-S jump of the summer monsoon front.3) Alkenone SST of the Japan Sea during MIS 5e was approximately 5 C higher than the present Millennial-scale variability of the SST is not distinct at Oki Ridge where influence of the Tsushima Warm Current was continuous, whereas the SST shows distinct millennial-scale variation in association with DOC due to the intermitted influence of the Tsushima Warm Current. Less