The Stalagmite Record Of Wanxiang Cave During The Transition Episode Of MIS3/2, In Eastern Qinghai-Tibetan Plateau

In palaeo-climate study, the last glaciation period was characterized by abrupt, millennial-scale climate change, existing a series of abrupt events and transformation progress. The abrupt events have been discovered and recorded by global documents, which have become the hotspot and focus of palaeo-climate research. With the reporting of geological record in different regional, extreme climate events are more and more obvious in regional area. There are debates about the internal structure, duration, conversion model of abrupt events, which leading different opinions about the mechanism levels of abrupt climate events. In addition, regional climate differences are very obvious in the climate transition zone, which is important time interval for exploring phrase change and drive factors in different regions. The Asian monsoon system is an important part of the global climate system, which connects the westerly belt to the north and the low-latitude over-equator monsoon system to the south, actively carries the meridional and zonal climatic signals transportation, in the capacity of a ligament of the high latitude ice caps-ocean system-atmosphere circulation. Meanwhile, the monsoon effected area load supporting a majority of population of our country, the advance and retreat of the monsoon which links to the precipitation variation relatives to national economy and the people’s livelihood. Hence, the research about the Asian monsoon system have an important and crucial scientific and reality significance.The climate of the eastern Qinghai-Tibetan Plateau Plateau,linking Qinghai-Tibetan Plateau of loess Plateau,is significant because it is under the influence of the East Asian monsoon system, an important component of the global climate system. Wanxiang Cave locates on the margin of modern summer monsoon effect area, northwest of China, the climate is semi-Arid, sensitively to the variation of the monsoon intensity. The climatic and hydrologic patterns in this region are very complex, and thus difficult to model, hence more accurate and detailed proxy climate data are necessary. Moreover, in this region, still lack of exactly dated high resolution climate records during the last glaciation. Hence, stalagmite records from Wanxiang Cave during this time period have an important scientific significance. In this paper, we choose a stalagmite from Wanxiang Cave, grown during the late time of last glaciation as our study object,11high precision230Th dating data,1033carbon and oxygen isotope pares were obtained and a10-yr resolution precipitation and vegetation evolution time series were established.Our research were to discuss the carbon and oxygen isotopes records during the late MIS3growth in the early MIS2, reconstructing the change of the monsoon and the vegetation status evolutionary sequences for the10years resolution during23-28.3kaBP on the base of wanxiang cave precipitation stable isotopes record features. Through the data analysis and comparison with other climate records(the record of the Asian monsoon change, the northern Greenland, the Antarctic ice core and the equator Marine records), got the main conclusions as bellow:To study the variations of δ D and δ18O in precipitation,32samples were sampled from Jan2002to Dec2002near Wan xiang cave, Gan su province, China. The δ D and δ18O values ranged from-64.7%o to-18.4%o and-18.4%o to-3.7%o, respectively. This wide range indicated that stable isotopes in precipitation were controlled by different condensation mechanisms as a function of air temperature and varying sources of moisture.δ18O in precipitation had a close positive relationship with the air temperature, clear temperature effect existed in this area. At a monthly scale, no precipitation amount effect existed. On the other hand, a weak precipitation effect still accrued at precipitation events scale. An observed strong seasonal influence occurred in the D-excess values. The results of backward trajectory of each precipitation day near wan xiang cave showed that the moisture of the precipitation in cold season (October to March) mainly originated from the westerly while the moisture source was more complicated in warm season (April to September)A10-year resolution cxygen isotope record from the Wanxiang Cave, based on6precise230Th dates and616oxygen isotopic measurements provide a detailed history of the Asian Monsoon from28.3to23ka B.P.A high-resolution oxygen isotopic record reveals decadal-centural oscillations in air temperature in the East Asian monsoon climate area during the early time of Marine isotope stadial2(MIS2). The most conspicuous feature in the oxygen isotopic record in the period is the particular cold event synchronized with the penultimate Heinrich event (H2) in the northern Atlantic deep-sea records. This particular cold event, beginning at24.6ka B.P, δ18O record demonstrates that the event lasted1200years with gradually cooling, which is different with δ18O record from Hulu cave and Tian e cave---a gradually cooling tendency after the remarkable cooling down. However, the δ O record from Wanxiang cave match well with δ18O record from Jin tan wan,Hunan province;The cooling event recorded in wanxiang cave also is consistent with δ18O record in GRIP. We believed that this unique pattern of event recorded in the stalagmite δ18O might be controlled by various factors including solar radiation, expanding of ice raft debrise in the northern Atlantic and sea surface temperature.The particular location of the Wanxiang cave makes the stalagmite δ18O easily affected by Asian winter monsoon and westly which correlated with Polar climate.Based on wavelet analysis and tranditional spectral analysis, the δ13C records of WX40D stalagmite have been analyzed during23～28.3ka B.P., which was sampled from Wanxiang cave located at the East of Qing hai-Tibetan plateau and the West of Chinese loess plateau in Wudu Country, Gansu province, China. The results show that major cycles of813C record of WX40D stalagmite is200a,148a,102a and the weak cycle is512a,254a on frequency scale using wavelet coefficient transformation technique. The time-frequency distribution of wavelet transform coefficient of δ13C record indicate10energy focus centers:which show the palaeo-vegetation bearing5remarkable transitions reflecting a clear palaeo-vegetation evolution history and its jump-points.The odd centers with negative δ13C record indicate high C3/C4responding to wet and warm climate conditions; Conversely the even centers always suggest dry and cold climate conditions.The wavelet transformation also shows that the δ13C record of stalagmite WX40D has multi-scale change characters. One big-scale cycle usually contains several small-scale cycles variation. The wavelet transform can effectively deal with the overlying palaeo-climate inform-ation, reduce artificial errors.The stalamites of the Wanxiang cave recorded the thousand and sub-thousand scale of climate extremely events, which is sensitive to temperature in high latitude of the north Atlantic area. Climate change which came from westerly zone and the northern high latitude have a strong effect in this area during the period of the monsoon recession. With the ice caps melting, the high-latitude climate system recession, and achieve the forces from sea level gradually rising, low latitude monsoon system gradually strong, the process of enhancing the effect gradually in the loess plateau in western China, stalagmite of wanxiang cave witness the transform of low and high latitude monsoon climate system. The monsoon record is strong related to solar radiation, indicating the monsoon climate in low latitude synchronously presents tele-connection with Northern Atlantic climate in higher latitude.