Orbital- and millennial-scale variations in Asian dust transport path to the Japan Sea
Orbital- and millennial-scale variations in Asian dust transport path to the Japan Sea
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DOI：
10.1016/j.palaeo.2006.11.027
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发表时间：
2007-04
期刊：
影响因子：
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通讯作者：
K. Nagashima;R. Tada;Hiroyuki Matsui;T. Irino;A. Tani;S. Toyoda
中科院分区：
文献类型：
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作者：
K. Nagashima;R. Tada;Hiroyuki Matsui;T. Irino;A. Tani;S. Toyoda
亚洲季风的轨道和千年尺度变化及其与Dansgaard-Oeschger（D-O）循环的可能联系已经被以前的研究所证实。然而，人们对这种变化的起源和性质知之甚少。日本海位于欧亚大陆干旱地区的下风处，因此接收了大量的风尘。因此，日本海的半远洋沉积物可能记录了一个连续的风尘堆积，这可能提供了亚洲季风过去变化的信息。为了了解亚洲季风的空间变化，利用日本海北方和南方的沉积物柱样，对沉积物中风尘的粒度、通量和物源进行了研究。由于在日本海的半远洋沉积物中的碎屑物质的粉粒部分主要由风成尘，粒度，通量和粉粒部分的来源进行了检查。根据石英的电子自旋共振（ESR）信号强度和结晶度，将塔克拉玛干黄土高原和西伯利亚东北地区确定为日本海沉积物中风尘的可能源区。此外，还根据ESR信号强度和石英结晶度估算了各源区风尘的相对贡献。在南部站点的两个源区的风沙通量进行了估计。6月北方观测站的沙尘颗粒大小和通量以及南方观测站的两个源区的沙尘通量均表现出与30° N太阳辐射变化相一致的轨道尺度变化。这些结果表明，在塔克拉玛干黄土高原和西伯利亚-东北地区，干旱区的范围和/或沙尘暴频率的轨道尺度变化，并建议向南西风急流轴向北移动，（减弱）冬季季候风，减少西伯利亚-中国东北地区冬季降水增加，或6月30° N低（高）日射期间夏季风界限向东南（西北）移动。除了这些轨道尺度的变化，千年尺度的变化可能与D-O循环中观察到的粒度记录在这两个网站的风尘。通过与轨道尺度变化的类比，认为这些千年尺度的变化反映了西风急流轴位置的千年尺度变化以及冬季风强度、冬季降水量和夏季风边界位置的变化。我们的研究结果表明，在西风急流和夏季风的限制，和冬季风的强度在轨道和千年的时间尺度上的变化的南北振荡。
Orbital- and millennial-scale variations in the Asian monsoon and its probable association with the Dansgaard–Oeschger (D–O) Cycles have been demonstrated by previous studies. However, the origin and nature of such variations are poorly understood. The Japan Sea is located down wind of the arid areas of the Eurasian continent, and thus receives significant amounts of aeolian dust. Consequently, the hemipelagic sediments of the Japan Sea are expected to record a continuous aeolian dust accumulation, which may provide information about the past variations in Asian monsoon. Grain size, flux, and provenance of aeolian dust in the sediments were examined using two sediment cores obtained from the northern and southern parts of the Japan Sea in order to understand the spatial variability of Asian monsoon. Since the silt fraction of the detrital materials in hemipelagic sediments of the Japan Sea is composed predominantly of aeolian dust, the grain size, flux, and provenance of the silt fraction were examined. The Taklimakan Desert–Loess Plateau and Siberia–Northeast China areas were identified as possible source areas of aeolian dust in the sediments of the Japan Sea based on the Electron Spin Resonance (ESR) signal intensity and crystallinity of quartz. Moreover, the relative contribution of aeolian dust from each source area was estimated based on the ESR signal intensity and crystallinity of quartz. Aeolian dust fluxes from the two source areas at the southern site were then estimated. Grain size and flux of eolian dust at the northern site, and fluxes of aeolian dust from two source areas at the southern site show orbital-scale variations in harmony with the insolation change at 30° N in June. These results indicate orbital-scale changes in the extent of the arid area and/or frequency of dust storms in the Taklimakan Desert–Loess Plateau and Siberia–Northeast China areas, and suggest that southward (northward) shifts of the westerly jet axis occurred together with either intensified (weakened) winter monsoon, decreased (increased) winter precipitation in the Siberia–Northeast China area, or southeastward (northwestward) shifts of summer monsoon limit during periods of smaller (larger) insolation at 30° N in June. In addition to these orbital-scale variations, millennial-scale variations possibly associated with the D–O Cycles are observed in the grain size record of aeolian dust at the two sites. Based on analogy with orbital-scale variations, these millennial-scale variations are considered to reflect millennial-scale changes in the position of the westerly jet axis together with the changes either in winter monsoon intensity, winter precipitation, or position of summer monsoon limit. Our results suggest N–S oscillations in the westerly jet and summer monsoon limit, and changes in the intensity of the winter monsoon on orbital and millennial timescales.