河北坝上地区湖泊沉积物记录的中全新世干旱气候

根据位于典型草原带的河北坝上地区白诺尔及毗邻的内蒙古乌兰诺尔湖泊沉积物的K、Na、Ca、Mg等化学元素组成、总有机碳(TOC)与氧同位素(δ¹⁸O)的分析,以(K+Na+Ca+Mg)/(Fe+Mn)值指示干旱度,1δ8O值指示夏季风的强弱,TOC值指示湖区植被状况,探讨了该地区¹⁴C测年9.8~5.3 ka B.P.以来的气候变化与环境变迁。结果表明:两个剖面所记录的气候变化趋势相近,¹⁴C测年7.0~5.7 ka B.P.为偏干期。反映夏季风强弱的氧同位素指标与干旱程度的变化没有明显的对应关系,说明夏季风引起的降水量变化不是气候干湿变化的主要影响因子,温度升高导致的蒸发加强可能对气候干旱化的影响更加明显。

Mid-Holocene Dry Climate Recorded by Lacustrine Sediments in Bashang Region of Hebei Province

Based on the analyses of chemical elements(K,Na,Ca,Mg,etc.),total organic content(TOC) and oxygen isotope(δ¹⁸O) of two lacustrine sediment sequences from Bashang area of Hebei Province and its surrounding,(K+Ca+Na+Mg)/(Fe+Mn) was demonstrated to well indicate aridity change.δ¹⁸O and TOC were adopted as proxies of intensity of summer monsoon and vegetation cover respectively.Climatic changes of this area during 9.8-5.3 ka B.P.were reconstructed.It is shown that climate changes of both sequences were quite similar and an arid stage from 7.0-5.7 ka B.P.was detected.However,the intensity of summer monsoon did not necessary correspond with the changes of aridity,implying that precipitation brought by summer monsoon in the study area was not the major factor of aridity change.On the other hand,evapotranspiration in the marginal area of Pacific monsoon,also called summer monsoon,was deterministic to the climatic aridity.