| Climate change closely influences human production and life, and Human beings urgently want to know the future climate change under the background of global warming. Based on the theory of astronomical climatology and paleoclimatic records, Marine isotope stage11(MIS11:-362-423ka) has been considered to be a good candidate for the present and future climate change, and climate change trend and amplitude increasingly drawn the attention of scholars. Because of the similar orbitally driven insolation and comparable atmospheric greenhose gas concentrations during the MIS11and Holocene, the process and characteristic of climae variations during MIS11could help us understand current climate change and further predict the future climate change trend. At present, this scientific problem has aroused researchers a lot of interesting, and many works has been done in marine sediments, ice core and terrestrial record. And the results of the study show that the marine isotope stage11is a super-interglacial and represents a warmest and longest period during the past600ka. Moreover, the preceding period of MIS12is a very important glacial period which represents extremely coldest glacial. Generally speaking, the existence of warmest and longest MIS11is closely relevant to MIS12super glacial. In addition, The MIS12/11transition (Termination V) is the most strongly glacial-interglacial transition process, and the global ice-volume, marine highstand and terrestrial records all change significantly during this period.Comparing to marine and ice core records, the terrestrial record has higher resolution, but they also deposit discontinuous, chronology constraint difficult and easily disturbed by regional environment. It is difficult for MIS11and neighboring stages research because of these characteristics. Fortunately, the Chinese loess deposit continually, and it completely record the East Asian monsoon (EAM) variation during the past2.5Ma. So, it is a better archive for MIS11study. Be confined to lower-resolution and higher pedogenesis-rate in the central Chinese Loess Plateau (CLP), we cannot fully understand the specific process and detail characteristic about stage11until now. However, the Jingyuan basin which sites in the west Liupan Mountain has the highest-resolution loess-soil sequences, because of the rich source of material, unique topography and special climate patterns. Consequently, it is an idea postion for MIS11research. The S4soil, interpreted as equivalent to MIS11, was investigated to construct the climatic variability during the periods of MIS12-10with proxies of grain size (GS), magnetic susceptibility (MS), total organic carbon (TOC) and soil color index (L*a*b*). In this area, our results suggested that the L4-L5sequence in Jingyuan profile in western CLP is much thicker (～40m) than that is in the central CLP areas (～12m). Furthermore, the S4soil (～12.9m) is also thicker than that in the central CLP (such as Luochuan loess section just about ～4m). Thus, the huge thickness of Jingyuan loess section menas a high-resolution and may contain unusually detailed paleoclimatic and environmental information which is not recorded in the central CLP. Besides these, In order to get the global and regional climate pattern, we also study the climate records in different climate system during MIS11. According to our reseach, we get the following conclusion: Baed on the existing dating results of paleomagnetism (PL), optical stimulated luminescence (OSL) and thermoluminescence (TL), we established the initial chronology of Jingyuan loess since the upper L6loess. Then after comparing with LR04and65°N summer insolation we contructed the finial hronology by applying the orbital tuning method (OTS). The results show that the whole stratigraphy lasted about650ka from SO to L6upper, and the duration of S4development sustained about65ka. However, the truly maximum interglacial of MIS11lasted only about30ka which is mainly corresponding to oxygen isotope stage11.3or11c. This result has a good consistency with the recently published results of Luochuan (LC) and Xifeng (XF) loess section as well as Lake Baikal and the Janpanese Biwa record. Accordingly, we further concluded that the MIS11.3was lasted about30ka at least.The evolution of Jingyuan loess-soil sequences from SO to L6shows a good glacial-interglacial characteristic in the orbital scale. Based on the initial chronology, the analysis in time-domain reveals～106,40and20-23ka period exist which clearly corresponding to eccentricity (～100ka), obliquity (～41ka) and precession (～19-23ka). Moreover, there also exist about187,96,64,49,32and29ka period, and these periods may be relevant to nonlinear feedback effects in climate system. Furthermore, the significantly different in dominant cycle between East Asian winter monsoon (EAWM) and East Asian summer monsoon (EASM) also reflects the climate variation characteristic is notebly different. In addition, the analysis in the frequency-domain shows that the domain period is discrepency in different proxies and different time period. However, the signal of eccentricity is abnormal remarkable during the S4soil formation, and it may play an obvious modulation role in the evolution of MIS11period. Further research also found that the climate is exetrmely dry and hot during the S4soil formation process comparing with the SO soil formation period, which means the MIS11climate is more dry and hot than that in the Holocene.S4soil is a significant marker horizon of the loess-soil sequences in the western CLP and represents the EASM strengthened period in the classical loess section in the central CLP. According to our research, the MIS11is warmer and wetness over the whole period. However, the climate change is not the same as ever during the S4evoltionary process, and it can be divided into three distinct phases. In the early stage, the climate is extremely warm and wet, and then the climate begain oscillation and gradually cooling down as well as the final stage the climate is relatively dry and cold. Unlikely what marine δ18O record shows MIS11is extremely stable, and the climate is intablility in the Jingyuan loess section. Moreover, further study shows that four times apparently climate change happened at～411ka、～401ka、～390ka and～369ka respectively, reflecting the climate in this region underwent periods:extremely warm-humid, briefly cooling, warm and humid and relatively cool period. Especially two sub-soils developed during briefly cooling period (S4SS1and S4SS2), but the the thickness of the weak soil is thiner and thiner. And the finally stage of MIS11, we think the climate maybe very similar to the MIS10glacial and the mountain glaciers in the western China may also have developed greatly. In addition, among these three climate changes timing, the climatic events which happened at～411and390ka were also recorded in Lake Baikal and Japanese Biwa. This may indicate the climate is instability during the early part of MIS11around the East Asian area at least.The climate is colder and drier during the preceding stage of MIS12and subsequent stage of MIS10, and the glacial feature is especially apparent. However, the stage12climatic evolution do not seems to what early discussed in marine record:the MIS12represented an extremely coldest super-glacial and the polar ice-caps and mountain ice sheet largely developed, and the the marine highstand is also lowest during this cloldest glacial period. On the contrary, the development of L5loess shows that the climate is relatively warm and humid during the middle period of MIS12(corresponding to MIS12.3) in the Jingyuan loess section. Moreover, further research reveals that these climatic oscillations (-3-4ka) are largely similar to D/O or H events which happened in the last glacial period. These events also recorded in marine sediments both in north and south high latitudes, and reveals that sub-orbital scale clmate osicillation event is ubiquitous around the worldwide. Nevertheless, the L4loess which is equivalent to MIS10shows an obivious glacial feature and the EASM strengtheded events is not recorded which was revealed by LC and XF loess section in the eastern CLP. The feature of L4loess is similar in many aspects to the marine record.Based on our orbital tuning chronology, we compare the record of loess with that of ice core, marine sediments as well as lake sediment during MIS11period. The results show that the MIS11.3happening time is almost similiarly (-405ka). We suspected some global forcing controlled the climate change during the early part of MIS11(MIS11.3or MIS11c). However, the climate record is strikingly different from MIS11.24to MIS10in loess, ice-core, marine and lake sediment. And we concluded that the climate variability during this period may largely controlled by global and regional forcing at same time. Furermore, the pattern of climate change during MIS11is most likely forced by65°N summer insolation. For examble, the insolation is strong and the regional forcing is relatively weak dring the early part of MIS11(MIS11.3or11c), so the climate is almost similarly around the world. On the contrary, the insolation is decreased during the later part of MIS11, thus the regional forcing is relative increased and the climate may show more regional feature. In addition to these, the terrestrial records are more sensitive to marine and ic-core record. And as to the terrestrial record, althouth the lake record climatic oscillation in the late period of MIS11, the amplitude and scale is smaller than loess. We further conclude that the loess record may be more sensitive to climate change than lake record in East Asian area.Finaly, we analyzed the development of S4soil in the whole CLP area. The result show that only one soil developed in the central loess plateau (such as LC, XF and chagnwu loess section, which is single in the MS), but there are two to three sub-soil developed in the north and western CLP (such as shimao and Jingyuan loess section which is multimodal in the indicator of MS). On the one hand, this phenomenon reflects clearly regional feature in the CLP duing the MIS11period. On the other hand, it also reflects the western and north regions around CLP are more sensitive to the global climate change than that in the CLP. Especially, according to the duriation of MIS11.3is gradually decreased from southeast to northwest, there may exist a climate pattern in CLP. Based on the predecessors study and our research, we reasonably concluded this pattern may be similar to the current climate pattern:warm-humid in the southeast CLP and Semi-arid sub-humid in the northwest areas. |
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