【作者】 徐丽娜；

【导师】 邵晓华；

【作者基本信息】 南京信息工程大学 ， 自然地理学， 2011， 硕士

【摘要】 轨道及千年尺度上中国南方石笋δ18O的变化多被认为指示了与夏季降水有关的夏季降雨量或夏季水汽源变化,也可能包含了冬季气温变化的信息,短尺度(年代际-百年)石笋δ18O波动的气候意义也被解释为夏季降雨量或水汽源变化。本文利用气象观测数据及同时段的石笋δ18O资料来检验短尺度上降雨量、水汽源或温度变化对中国南方石笋δ18O的波动的影响。中国南方同一洞穴或不同洞穴石笋氧同位素序列具有较好的重复性,在与气象观测数据长度重叠的时段(近50年)中都呈现了偏正的趋势,可能是受记录分辨率差异的影响,偏正的速率并不一致,整体变化趋势的一致性仍然表明：应该是来自岩溶系统外部的相同机制控制了南方石笋δ180年代际至百年际尺度的波动。通过分析这些洞穴附近气象站点的降水数据,本文发现近50年和尚洞和董歌洞所在区域的夏季降水量和夏季降水占全年降水比例均呈增大趋势,仅考虑夏季降水量的变化,那么这些地区降水δ18O的长期趋势应是偏负。研究区夏季大气降水方程和区内七个GNIP站点夏季降水δ18O数据的逐月相关性分析结果表明：中国南方绝大部分区域夏季降水来自西南通道输送的海洋气团。利用1951-2000年NCAR/NCEP再分析资料计算的中国南方水汽通量结果进一步说明近50年西南通道一直是中国南方夏季水汽输送的最主要通道,因此夏季水汽源的变化也不能解释石笋618O的偏正趋势。两个洞穴附近气象站点温度数据显示洞穴所在区域年均温的变率在+0.03℃/10a～+O.15℃/10a之间,若仅考虑年均温对降水δ18O的影响,那么本文所计算的温度增加可引起降水8180的偏正速率为+0.012‰～+0.105‰/10a,石笋δ18O近50年的偏正速率与这一结果相符。由此本文认为,石笋δ180年代际-百年尺度波动很可能反映了大气温度的变化。更多还原

【Abstract】 Variability in oxygen isotope ratios collected from speleothems in the caves located in southern China is often interpreted as a proxy for variability of summer precipitation (the ratio of summer to winter precipitation), or the summer water vapor source. Some researchers argue that the winter temperature change also has strong impact on caveδ18O. Here we use the observed meteorological data and the contemporary stalagmiteδ18O records to test whether the decadal-centennial variability ofδ18O cave over southern China can be related to changes in climate. Recently published stalagmiteδ18O records from Heshang cave and Dongge cave in southern China all display gradually enriched trends during the last 50 years. During the period examined, the amount of summer precipitation and the ratios of summer to annual precipitation exhibit positive trends over the region where the caves are located. If the same seasonal moisture sources and transport pathways have prevailed in the past 50 years, a positive liner trend of the amount of summer rainfall (the ratio of summer to annual precipitation) should lead to a negative liner trend of stalagmiteδ18O values. And the results of correlation analysis between monthly summer precipitationδ18O data from seven GNIP stations indicate that most of the region’s precipitation is from southwesterly water vapor fluxes for 1986-1992. The annual summer transport of water vapor to southern China is evaluated using the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis for 1951-2000. Results indicate that the same seasonal moisture sources and transport pathways have prevailed over southern China during the last 50 years. Thus, neither the change of the amount of summer precipitation, nor the variability of summer water vapor source plays an important role on the long-term increasing trend of precipitationδ18O data during the last 50 years. We calculated the linear trend through the last 50 years of temperature data for eight stations near the two caves. The results show generally positive trends (+0.03℃per decadal to+0.15℃per decadal), which may induce a positive trend in precipitation of+0.012%o per decadal to+0.105%o per decadal, consistent with the trend in stalagmiteδ18O records during the last 50 years. The enriched trend recorded in stalagmite records from southern China during the last 50 years, also expressed by the other Chinese and Oman stalagmite records, may be controlled by global warming.更多还原