雁荡山湖泊沉积物记录的中国东部季风区小冰期以来气候干湿变化

Climate change in the monsoon region of eastern China since the Little Ice Age(LIA)recorded from Lacustrine sediments in Yandang Mountain

中国东部季风区过去千年降水变化特征已有大量研究并取得重要进展,但多数研究集中在中国北方和中部地区,南方地区重建记录相对较少.本文对浙江雁荡山雁湖沉积物的总有机碳、色度和粒度等多指标进行分析,重点探讨小冰期以来研究区域的降水变化,结果显示:1)1400-1600 AD,湖区集水发育,研究区气候偏湿润;2)1600-1650 AD,降水量减少,气候偏干旱;3)1650-1750 AD,气候偏湿润;4)1750-2000 AD,研究区气候处于干旱状态,其中1500-1650 AD期间的干湿变化与历史文献记录的雁湖水位有良好的对应关系.在年代误差范围内,雁湖沉积物与浙江天目山泥炭、福建仙山泥炭以及湖光岩玛珥湖沉积物等记录的干湿变化同步,指示了小冰期期间中国东南地区气候波动的一致性.另外,中国东部南、北地区古气候记录反映的降水变化趋势相反,表明在百年时间尺度上,中国东部南北地区降水存在着"南涝北旱"和"北涝南旱"的空间特征.通过与太平洋年代际振荡(PDO)的对比,显示PDO对中国东部地区小冰期期间出现的南-北"偶极型"空间降水特征可能具有重要影响.

Numerous studies have been conducted to investigate precipitation variation in the monsoon region of eastern China during the past millennium,however,most of them have mainly focused on the records from northern and central China,thus lacking of precipitation records from southern China.In the present study,we carried out multi-proxy analyses of lacustrine sediments from Yandang Mountain in Zhejiang Province of southern China,including total organic carbon(TOC),chromaticity,and grain size,to reconstruct past hydroclimatic changes since the Little Ice Age(LIA).The results show that:1)during 1400-1600 AD,the lake expanded and the climate was relatively humid;2)during 1600-1650 AD,precipitation decreased and the climate was drier;3)during 1650-1750 AD,the climate became wetter;4)during 1750-2000 AD,the climate remained relatively dry.It is noteworthy that during the period from 1500 to 1650 AD,humidity reconstruction from this study corresponds well with historical documents.Within uncertainties of the age calibrations,changes in our record are similar to those in the peat records from the Tianmu Mountain in Zhejiang Province,the Xianshan Mountain in Fujian Province,and the lacustrine records from Huguangyan Maar Lake,indicating the consistency of climate fluctuations in southeast China.In addition,the paleoclimate records of northern and southern regions in eastern China have the opposite trend of precipitation.It is suggested that,on the centennial scale,the precipitation variations in eastern China were characterized by the asynchronous pattern of moisture variations between northern and southern regions,i.e."dry in northern China and wet in southern China"or"wet in northern China and dry in southern China".The comparison with the Pacific Decadal Oscillation(PDO)shows that PDO plays an important role in the spatial precipitation characteristics of the"south-north"dipolar mode during the LIA in eastern China.