福建漳浦六鳌海岸沙丘记录的近300年气候环境演变

通过对福建漳浦六鳌海岸沙丘剖面（CD2）粒度特征成因分析,阐明了该剖面沉积具有典型海岸风成砂特点,其粒度参数记录了海岸带风力作用的变化.根据海岸变迁历史分析,并以敏感组分粒级含量变化曲线与国内外具有精确时标的气候曲线进行对比,初步建立了所研究剖面的年代学标尺.在此基础上,采用粒级-标准偏差方法提取敏感粒度组分,作为海岸带风力作用强度变化的替代指标,建立了约300年来福建东南沿海气候环境演变序列.结果显示：1）1690-1790年,冬季风较强,总体呈现缓慢减弱的趋势,气候表现为冷干的特点;2）1790-1900年,冬季风不断减弱,气候表现为暖湿的特征;3）1900-1960年,冬季风快速增强,显示快速增温的气候特点.通过与甘肃万象洞石笋δ^18O曲线振幅和波动特点细节对比,CD2剖面海岸风沙沉积记录的小冰期以来的气候不稳定性更为突出,这或许表明,我国南亚热带季风边缘对全球气候变化的响应具有一定程度的放大效应.

The Climatic and Environmental Evolution of the Coastal Dunes Since 300 Years Ago in Liuao Island,Zhangpu County,Fujian Province

Based on the analysis of the causes of grain size parameters in Zhangpu of Fujian, we find that the CD2 profile has typical characteristics of coastal aeolian sands. Therefore, the change of its grain-size parameters is likely to record the range ability of coastal wind force. According to the historical changes of coastline and the comparison of sensitive grain-size curve of coastal dunes with at home and abroad climate curves which have precise time scale, we establishes the CD2 profile＇ s geochronology scale. On this basis, we get sensitive grain size group in CD2 profile by using grain size-standard deviation method. Then by taking it as a surrogate marker of the winter monsoon, we have reconstructed the record of climatic and environmental evolution since about 300 years ago in the southeast coast of Fujian Province. The results indicate that： （1）1690-1790AD, winter monsoon was strong and its whole trend was weakening, the climate was cold-dry;（2）1790-1900AD, the winter wind was dwindling and the climate was warm and humid; （3）1900- 1960AD, the winter monsoon was weakening quickly and the climate was warming rapidly as well. By comparing the sensitive grain-size curve of coastal dunes with the δ^18O curve＇ s details of stalagmite in Wanxiang Cave of Gansu, we can found that the instability of coastal dunes in CD2 profile is more prominent when characterizing the wave of climate since the Little Ice Age. which may indicate a certain degree of amplification effect of the edge of the south subtropical monsoon zone response to global climate change in our country.