High resolution reconstruction of paleoclimate around the Japanese alpine area based on lake sediments analyses

根据诺吉里湖钻探的湖泊沉积物，详细重建了过去6万年的古气候。总有机碳(TOC)和总氮(TN)可作为古气候和孢粉分析的新的优良指标。这些数据平均间隔约50年，可以提供东亚地区末次冰期和冰后期的标准气候变化之一。长野市高野组钻探的沉积物长54.5m，由均匀的粉质粘土组成，并夹杂着许多Tephra层。几种广布标志物的放射性年龄为沉积物年龄估算提供了关键。TOC和TN的测定间隔为1 cm，平均为26年。16万~4万年间，TOC和TN含量的垂直分布与海相和格陵兰冰芯的~(18)O同位素曲线一致。这是首次详细重建日本陆地地区的古气候，在时间分辨率和覆盖率方面是日本及其周边地区最好的古气候数据之一。这些数据可以作为日本古气候的标准，因为它们可以通过Tephra型标志物与其他地区进行对比。另一方面，我们试图阐明湖泊沉积物中TOC和TN含量如何反映气候变化的过程。1982-2002年，对日本中部奇崎湖沉积物中总有机碳含量与湖水生物生产力和气候因子之间的现代关系进行了研究。研究表明，冬季温度控制着湖水的年生物生产力，导致有机质的积累，冬季温度是指冷季持续时间。

The paleoclimate during the last 60,000 years have been reconstructed in detail, based on the drilled lake sediments from Lake Nojiri. Total organic carbon (TOC) and total nitrogen (TN) are used as new excellent proxies of paleoclimate as well as pollen analysis data. These data have about 50 years interval in average, and can provide one of standard climate changes around East Asia in the Last Glacial and Post-glacial periods.The drilled sediments of Takano Formation in Nagano City, 54.5 meters long, is composed of homogenous silty clay, and are intercalated with many tephra layers. Radiometric ages of several wide-spread marker tephras offers keys of age estimation of sediments. TOC and TN contents are measured in 1cm interval, about 26 years average. The vertical profile of TOC and TN contents varies concordantly with marine ^<18>O isotope curve and also with ^<18>O isotope curve of Greenland ice cores from 160,000 years to 40,000 years age. This result is the first detailed reconstruction of paleoclimate of Japanese land area.These reconstructions are one of best paleoclimate data in and around Japan in time resolution and long coverage. These data can be a standard of paleoclimate in Japan, because they can be correlated with other areas by the means of marker tephra.On the other hand, we have tried to clarify the process how TOC and TN contents in lake sediments reflect climate change. The modern relationship among TOC contents in sediment, biological productivity of lake water and weather factors in Lake Kizaki, central Japan were examined from 1982 to 2002. The study have revealed that winter temperature which means duration of cold season, control annual biological productivity in lake water, resulting in the amount of accumulated organic matters.