过去对北非和中国干旱区140 ka BP来环境演化的初步对比表明,两地的干旱度在万年时间尺度上基本同步。这种关系是否也适用于全新世百年尺度的干旱事件,仍是有待研究的问题。本文对撒哈拉地区569个地表淡水指示物和我国北方干旱区158个...过去对北非和中国干旱区140 ka BP来环境演化的初步对比表明,两地的干旱度在万年时间尺度上基本同步。这种关系是否也适用于全新世百年尺度的干旱事件,仍是有待研究的问题。本文对撒哈拉地区569个地表淡水指示物和我国北方干旱区158个古土壤和湖泊沉积的^(14)C年代数据进行了时空频数统计分析,揭示出两地沙漠在全新世期间至少经历了三次同时性的、百年—千年尺度的干旱事件,叠置于季风气候对地球轨道变化响应的总体趋势上;沙漠在纬向上的进退主要受控于季风前沿的伸缩幅度,说明两个季风系统的短尺度变化可能受统一因素控制。最为显著的干旱事件发生于约4 ka BP。两地干旱区在过去认为的6 ka BP前后的全新世气候适宜期并没有表现为稳定的湿润环境。我国过去发现的该时期不少的干旱证据被解释为高温所导致的强烈蒸发作用所致。但全新世中期的干旱期在热带的存在及其与冰心记录中低甲烷事件的吻合难以用蒸发来解释,而应与夏季风环流的减弱有关。展开更多
This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water disch...This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales： 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.展开更多
Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka...Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka B. P. could correspond to the onset of the 100 ka cycle during the glacial and interglacial periods. This abrupt change in the 100 ka cyclicity at 600 ka B. P. occurred also in the magnetic susceptibility signal that is obtained from and paleosol sequences of the China Loss Plateau. The larger amplitude and stronger cyclicity in the susceptibility signal after 600 ka B. P. reflect the prominent change in the intensity of the monsoon, induced by an enhancement of the momsoon circula- tion. Stronger seasonality during the glacial period in the South China Sea, resulted from strengthening of winter monsoon, might lead to the changes in the radiolarian composition at 600 and 120 ka B. P. It can be suggested that only species adapted to a broader temperature range might have been able to live in this environment. Therefore, the abrupt changes in radiolarian composition at 600 and 120 ka B. P. could be attributed to the stronger so differences between summer and winter that were caused by the striking change in the intensity of the monsoon circulation.展开更多
利用1959~2016年海河流域57个站点的降水资料,采用最小二乘趋势拟合、Mann-Kendall非参数检验和Morlet小波等方法,分析了海河流域降水的趋势、突变及周期特征。结果表明:近60年来,海河流域降水总体呈减少趋势,线性倾向率为?0.57 mm a-2...利用1959~2016年海河流域57个站点的降水资料,采用最小二乘趋势拟合、Mann-Kendall非参数检验和Morlet小波等方法,分析了海河流域降水的趋势、突变及周期特征。结果表明:近60年来,海河流域降水总体呈减少趋势,线性倾向率为?0.57 mm a-2;海河流域降水空间的总趋势是由中北部平原区分别向西北和东南两侧减少;没有检测到明显的突变过程;海河流域降水量存在2.5年、4.9年显著周期(P <0.05),以及9.8年、16.5年和23.4年非显著性周期。显著性周期主要发生在1959~1976年和1986~2005年。根据近60年降雨规律,2005~2016年海河流域处于降水偏少期,预测未来几年很有可能向降水充沛期过渡。展开更多
文摘过去对北非和中国干旱区140 ka BP来环境演化的初步对比表明,两地的干旱度在万年时间尺度上基本同步。这种关系是否也适用于全新世百年尺度的干旱事件,仍是有待研究的问题。本文对撒哈拉地区569个地表淡水指示物和我国北方干旱区158个古土壤和湖泊沉积的^(14)C年代数据进行了时空频数统计分析,揭示出两地沙漠在全新世期间至少经历了三次同时性的、百年—千年尺度的干旱事件,叠置于季风气候对地球轨道变化响应的总体趋势上;沙漠在纬向上的进退主要受控于季风前沿的伸缩幅度,说明两个季风系统的短尺度变化可能受统一因素控制。最为显著的干旱事件发生于约4 ka BP。两地干旱区在过去认为的6 ka BP前后的全新世气候适宜期并没有表现为稳定的湿润环境。我国过去发现的该时期不少的干旱证据被解释为高温所导致的强烈蒸发作用所致。但全新世中期的干旱期在热带的存在及其与冰心记录中低甲烷事件的吻合难以用蒸发来解释,而应与夏季风环流的减弱有关。
基金National Natural Science Foundation of China, No.41271026
文摘This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multi-scale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The Mann-Kendall test, order clustering, power-spectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at inter-annual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales： 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, large-scale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.
基金This project was supported by the National Natural Science Foundation of China under contract! Nos 49946011 and 49999560 by
文摘Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka B. P. could correspond to the onset of the 100 ka cycle during the glacial and interglacial periods. This abrupt change in the 100 ka cyclicity at 600 ka B. P. occurred also in the magnetic susceptibility signal that is obtained from and paleosol sequences of the China Loss Plateau. The larger amplitude and stronger cyclicity in the susceptibility signal after 600 ka B. P. reflect the prominent change in the intensity of the monsoon, induced by an enhancement of the momsoon circula- tion. Stronger seasonality during the glacial period in the South China Sea, resulted from strengthening of winter monsoon, might lead to the changes in the radiolarian composition at 600 and 120 ka B. P. It can be suggested that only species adapted to a broader temperature range might have been able to live in this environment. Therefore, the abrupt changes in radiolarian composition at 600 and 120 ka B. P. could be attributed to the stronger so differences between summer and winter that were caused by the striking change in the intensity of the monsoon circulation.
文摘利用1959~2016年海河流域57个站点的降水资料,采用最小二乘趋势拟合、Mann-Kendall非参数检验和Morlet小波等方法,分析了海河流域降水的趋势、突变及周期特征。结果表明:近60年来,海河流域降水总体呈减少趋势,线性倾向率为?0.57 mm a-2;海河流域降水空间的总趋势是由中北部平原区分别向西北和东南两侧减少;没有检测到明显的突变过程;海河流域降水量存在2.5年、4.9年显著周期(P <0.05),以及9.8年、16.5年和23.4年非显著性周期。显著性周期主要发生在1959~1976年和1986~2005年。根据近60年降雨规律,2005~2016年海河流域处于降水偏少期,预测未来几年很有可能向降水充沛期过渡。
