Investigation on trigger of Asian monsoon intesities by using lake, shallow-sea and loess sediments

在西欧的马尔湖和日本的咸水湖中，往往有保存完好的变异沉积物。利用这些阀进行了末次冰期以来气候和古环境变化的高分辨率重建的许多年代学和沉积学研究。特别是意大利Lago Grande di Monticchio （Zolitschka and Negendank, 1999）和日本Suigetsu湖（Kitagawa and Van der Plicht, 1998; Fukusawa, 1999） 45000年以来，利用碎屑沉积物重建的准确年代学和高分辨率古环境变化，成为第四纪研究的热点。我们希望研究海洋和大气环流对全球气候变化的触发因素和诞生地。因为全球气候系统是地球科学领域的几个重大问题。其中一个问题是“气候系统在哪里引发了第一次影响？”Blunier et al. (1998) sh . More揭示了格陵兰岛和南极洲冰芯数据之间的相互关系。末次冰期南极冰芯的气候突变似乎先于格陵兰（Blunier et al., 1998）。目前，全球气候变化研究的主要研究地点有以下三个：北大西洋是海洋输送带的诞生地，南极洲是冰量生成区，西太平洋低纬度地区是暖池。我们的研究将为探讨西太平洋暖池是否是诞生地提供许多信息。因为亚洲季风的强度受冬季西太平洋低纬度地区和喜马拉雅/青藏高原冰雪覆盖地区的海温大小的控制。通过对东亚不同湖泊沉积物通量（mg/cm 2yr）的检测，将为解决我们的问题提供许多信息。在水越湖阀计数的基础上，精确、高分辨率地计算了沉积速率。根据不同沉积物的风成伊利石和石英通量，中国黄土高原等沙源区自15500年以来由于植被扩张导致沙尘通量减少。而水越湖夏季层状水团形成于14000年BP，主要原因是铁矿物的主要成分由富锰的维氏铁矿向菱铁矿转移。此外，自约16000年BP以来，由于地表水初级产量的增加，有机碳通量有所增加。这些事实表明，在水越湖初级生产增加之前，亚洲内陆地区的植被扩大了。四个古气候记录大致相似，但不详细。除前寒武纪外，日本风沙通量在沸腾暖期开始时的急剧下降速度快于GISP2 δ 180变化的增加速度，在新仙女木期开始时的下降速度也更快。自16000年BP以来，尽管水越湖水体变暖，但浮游植物初级生产的有机碳通量有所增加。这些证据为我们提供了三个重要的古气候信息：1) 16000年以来，亚洲夏季风引起的温暖湿润气候由日本列岛向中国内陆地区扩展。2)亚洲大陆内部气候变暖的突变速度比GISP2冰芯更快，时间滞后超过1000年。③全球气候变化的触发点位于格陵兰冰盖周围的低纬度地区，而不是高纬度地区，因为低纬度地区的气候变化先于高纬度地区存在。第三个证据支持王玲珑教授（Wang et al., 1999）关于气候对全球变化影响的诞生地理论。他的理论认为，西太平洋暖池的变化对全球变化产生了最初的影响。少

There are often well-preserved varved sediments in maar lakes of western Europe and brackish-water lakes of Japan. Many chronological and sedimentological studies for high-resolution reconstruction of climatic and paleoenvironmental changes since Last Glacial have been carried out by using these varves. In particular, accurate chronology and high-resolution changes of the paleoenvironment reconstructed by using varved sediments since 102,000 yrs BP at Lago Grande di Monticchio, Italy (Zolitschka and Negendank, 1999) and since 45,000 yrs BP at Lake Suigetsu, Japan (Kitagawa and Van der Plicht, 1998 ; Fukusawa, 1999) has attracted scientific attention in Quaternary research.We hope to investigate triggers and birth place of global climatic changes on ocean and atmospheric circulations. Because there are several big questions on global climatic system in earth science field. One of these questions is "Where have given first impact to climatic system as a trigger?" Blunier et al. (1998) sh … More ows interrelationships among ice core data in Greenland and Antarctica presenting. Abrupt climatic changes during Last Glacial in Antarctica ice core seem to go ahead of those in Greenland (Blunier et al., 1998). Now, place of dispatch on global climatic change are presumed 3 main sites by many researchers as follows ; North Atlantic as birth place of ocean belt conveyor, Antarctica as ice volume product area, and low latitude area of West Pacific as warm pool. Our research will give many information to discuss whether warm pool of western Pacific is birth place or not. Because Asian monsoon intensity are controlled by magnitude of sea surface temperature in low latitude area of West Pacific and of snow covered area on the Himalayan / Tibetan Plateau in winter season. Research of varved lacustrine sediments in East Asia will give many information to solve our questions through detection of Sediment flux (mg/cm 2yr). We calculated accurate and high-resolution sedimentation rate on the base of varve counting in Lake Suigetsu varve. According to eolian illite and quartz fluxes in varved sediments, decreasing of dust flux due toexpansion of vegetation in dust source area such as Chinese Loess Plateau occurred since 15,500 years BP. However, stratified water massin summer at Lake Suigetsu appeared since 14,000 years BP, because main componets of iron minerals transported from Mn-rich vivianaite to siderite. Also, Organic carbon flux due to increasing primary production in surface water have increased since about 16,000 years BP. These facts indicate that vegetation in the inland area of Asia expanded before primary production increased in Lake Suigetsu. Four paleodimate records are roughly similar, but not in detail. Abrupt decreasing of eolian dust flux occurred in varve sequence of Japan was more quickly than increasing of delta 1 80 changes in GISP2 in the onset of the Boiling warm period except Pre-Boreal, and also decreasing rate was more quickly in the onset of the Younger Dryas period. Organic carbon flux originating from primary productions by phytoplankton increased since 16,000 years BP, though warming in water mass of Lake Suigetsu. These evidences give us three important paleoclimatic information as follows ; 1)Warm and humid climate by Asian summer monsoon expanded from Japanese Islands to the inland area of China since 16,000 years BP. 2) Abrupt onset of warming climate in inner area of Asian Continent occurred more quickly than that of GISP2 ice core with time lags more than 1,000 years. 3) Trigger of global changes was located at low latitudes rather than high latitudes around Greenland ice sheet because of existence of climatic changes at low latitudes prior to at high latitudes. Also, third evidence supports Prof. Wang Linglang's theory (Wang et al., 1999) about birth place of climatic impact to global changes. His theory suggests that changes of warm pool in West Pacific gave initial impact to global changes. Less