大兴安岭北部满归泥炭孢粉重建的过去2100年古气候

大兴安岭地处季风气候的尾闾区,是一个研究全球变化的关键区域.但由于该地区古气候代用指标(树轮、孢粉、石笋等)获取比较困难,历史文献也缺乏,使得古气候研究受到了限制.本研究通过大兴安岭北部的漠河县满归镇附近一个厚88 cm的泥炭剖面的孢粉记录,根据831个表土样品的花粉数据和附近90个气象台站30年的地面观测数据,运用现代类比法( Modern Analogue Technique,简称MAT)重建了该地区过去2100年的年均温(Tann)、年降水量(Pann)、 1月均温(Tjan)和7月均温(Tjuly),结果表明Tann和Tjan的波动达到2. 4℃, Tjuly的波动为1. 7℃, Pann波动为28. 2 mm.该地区的气候变化分为3个阶段:阶段Ⅰ(150 BC^850 A.D.)温度和降水量相对较低,年均温比现代30年均值低约0. 5℃;阶段Ⅱ(850~1300 A.D.)以温度升高-降低的波动为特征,升温在1070~1170 A. D.期间最明显,年均温比现代 30 年平均值高 0. 2℃,这一时期相当于欧洲中世纪气候异常期( the Medieval Climate Anomaly,简称MCA);阶段Ⅲ(1300~2000 A.D.)早期(1300~1900 A.D.)以气温较低为特征,这一时期相当于小冰期(the Little Ice Age,简称LIA),年均温比现代30年平均值低0. 8℃,晚期(1900~2000 A.D.)呈现升温的趋势.

Pollen-based climate reconstruction during the past 2100 years from the MG peat profile in the northern Daxing'an Mountains

The past two millennia is a critical period for understanding the factors responsible for the variability of the global climate system.The reconstruction of high-resolution temperature and precipitation sequences during the past 2000 years in many regions of China has been carried out using climate proxy records, such as historical documents, tree rings, pollen, corals, lake sediments, stalagmites, ice cores, and so on.However only limited such studies have been restricted in the Daxing'an Mountains due to the lack of suitable climate proxy records, while this region is a key area for studying global climate changes given its location in boundary zone of the monsoon climate. This study is based on a pollen record of the 88-cm long MG peat profile located 20 km north of Mangui town in the northern Daxing'an Mountains (52°17'39.88"N, 122°08'40.07"E;665 m a.s.l).The modern meteorological parameters of the site are obtained by spatial interpolation of 30-year average meteorological data of nearby stations:annual mean temperature -4.6℃, annual precipitation 455.4 mm, January mean temperature-29.5℃, and July mean temperature 17.2℃.A total of 831 surface pollen samples and the 30-year ground observation data of 90 meteorological stations are used in the Modern Analogue Technique (MAT) to reconstruct the annual mean temperature (Tann), annual precipitation (Pann), January mean temperature (Tjan) and the July mean temperature (Tjuly) for the past 2100 years in this region.The results reveal regional climate change during the past 2100 years:the Tann fluctuates between-3.1℃ and-5.5℃ with the average value of-5.1±0.3℃;the Tjan fluctuates between-27.4℃ and-29.8℃ with the average value of-29.4±0.4℃;the Tjuly fluctuates between 15.9~17.6℃ with the average value of 16.4±0.2℃;the Pann varies between 471.3 mm and 499.5 mm with the average of 479.3±4.2 mm.The climate change of the past 2100 years can be divided into three stages.Stage I (150 BC^850 A.D.):the temperature and precipitation were relatively low, and the Tann was about 0.5℃ lower than the modern 30-year mean.Stage Ⅱ(850~1300 A.D.):temperature fluctuation occurred and marked temperature rose during the period 1070~1170 A.D.with the Tann of-4.4±0.2℃, which is about 0.2℃ higher than the modern 30-year mean.This stage is referred to the European medieval climate anomaly (MCA).Stage Ⅲ(1300~2000 A.D.):the period 1300~1900 A.D.correlating with the Little Ice Age (LIA) was characterized by lower temperature with the Tann of-5.4±0.2℃, which is about 0.8℃ lower than the modern 30-year mean.However the temperature show a warming trend since 1900 A.D.