A climatic reconstruction in historical times based on the freezing date records and sediment cores at Lake Suwa

在1996年夏天，我们提取了2米长（约800年）的沉积物岩心样品从Suwa湖使用活塞取样器。对湖泊沉积物样品每隔2.5cm进行切片，分析颜色质量、磁化率、比重、矿物组成以及碳、氮和硫的含量。结果表明，有机碳含量是反映气候变化的有效指标。因此，我们研究了近500年来湖泊沉积物柱样的有机碳含量与Suwa湖的冻结日期之间的关系，并试图根据Suwa湖冻结日期的长期记录，使用线性回归方程（r=0.80）来估计冬季温度。估计的冬季温度时间序列表明，17世纪初是最冷的时期，而1480年代和1540年代都相对温暖。18世纪50 - 60年代，日本气温呈上升趋势，饥荒频繁发生。

In the summer of 1996, we extracted 2m long (around 800 years) sediment core samples from Lake Suwa using a piston corer. Sampled lake sediments were sliced in every 2.5 cm to analyze the color quality, the magnetized ratio, the specific gravity, the mineral composition, and the content of carbon, nitrogen and sulfur. The results show that organic carbon content is an effective indicator of climatic variations. Thus we examine the relationship between the organic carbon content of Lake sediment cores and the freezing dates of Lake Suwa for the last 500 years.An attempt was made to estimate winter temperatures based on the long term record of the freezing dates of Lake Suwa using the linear regression equation (r=0.80). Estimated winter temperature time-series indicated that early 1600's was a coldest period, whereas both 1480's and 1540's were relatively warm. Temperature showed increasing trend from 1750's to 1860's, during which severe famine occurred frequently in Japan.