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

根据Nojiri湖钻探的湖泊沉积物，详细地重建了过去6万年的古气候。总有机碳（TOC）和总氮（TN）是研究古气候和花粉分析的新指标。这些数据的平均间隔约为50年，可以提供东亚地区末次冰期和后冰期的标准气候变化之一。长野市高野组钻孔沉积物长54.5米，由均质粉质粘土组成，并嵌有许多层状体。几种分布广泛的标志岩的辐射年龄为沉积物的年龄估计提供了关键。TOC和TN的测定间隔为1cm，平均值约为26年。TOC和TN含量的垂直剖面与海洋^<18>O同位素曲线和格陵兰冰芯^<18>O同位素曲线在16 ~ 40000年的变化一致。这是日本陆地地区首次详细重建古气候。这些重建是日本及其周边地区时间分辨率和覆盖范围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，因为它们可以通过标记温度与其他地区进行对比。另一方面，我们试图阐明湖泊沉积物TOC和TN含量反映气候变化的过程。对1982 ~ 2002年日本中部木崎湖沉积物TOC含量、湖水生物生产力和气象因子的现代关系进行了研究。研究表明，冬季温度，即寒冷季节的持续时间，控制着湖泊水体的年生物生产力，从而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.