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

根据从野尻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）是新的古气候和孢粉分析数据的优良指标。这些资料的平均间隔约为50年，可以提供东亚地区末次冰期和冰后期气候变化的标准资料之一。长野市高野组钻孔沉积物长54.5m，由均匀的粉质粘土组成，夹有许多火山灰层。几个分布广泛的标志火山岩的放射性年龄为沉积物的年龄估算提供了依据。TOC和TN含量每隔1cm测定一次，约26年平均。TOC和TN含量的垂向变化与海洋^<18>O同位素曲线和<18>格陵兰冰芯16 ~ 4万年的^ O同位素曲线一致。这是首次对日本陆地地区的古气候进行了详细的重建，这些重建是日本及其周边地区在时间分辨率和覆盖范围方面最好的古气候数据之一。这些数据可以作为日本古气候的一个标准，因为它们可以通过火山灰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。从1982年到2002年，研究了日本中部木崎湖沉积物中TOC含量、湖水生物生产力和天气因素之间的现代关系。研究表明，冬季温度即寒冷季节的持续时间，控制着湖泊水体全年的生物生产力，导致有机质的积累量。

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.