Origin of the middle Pleistocene transition by ice sheet erosion of regolith
Origin of the middle Pleistocene transition by ice sheet erosion of regolith
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DOI：
10.1029/97pa02660
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发表时间：
1998-02-01
期刊：
影响因子：
--
通讯作者：
Pollard, D
中科院分区：
文献类型：
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作者：
Clark, PU;Pollard, D
δ(18)O深海岩心记录中更新世中期（类似于0.9 Ma）在基本相同的轨道强迫下从相对低幅度、高频（41 kyr）到高幅度、低频（100 kyr）冰体积变化的转变可归因于从全软层劳伦泰冰盖到混合硬软层劳伦太德冰盖的变化。 冰川侵蚀厚厚的风化层，导致未风化的结晶基岩暴露。一维冰盖和基岩模型（包括冰下沉积物变形引起的沉积物和冰的运输）表明，广泛变形的沉积物层在转变之前保持薄冰盖，其对主要（23 和 41 kyr）轨道强迫呈线性响应。沉积物层的逐渐去除最终导致向更厚的冰盖过渡，其主要变化时间尺度（100 kyr）反映了非线性的冰消过程。在过去 3 Ma 的模型模拟中，在没有冰和均匀的 50 m 沉积层的情况下初始化，冰体积和范围的时间序列在几个重要方面与观测记录一致。
The transition in the middle Pleistocene (similar to 0.9 Ma) seen in delta(18)O deep-sea-core records from relatively low-amplitude, high-frequency (41 kyr) to high-amplitude, low-frequency (100 kyr) ice volume variations under essentially the same orbital forcing can be attributed to a change from an all soft-bedded to a mixed hard-soft bedded Laurentide ice sheet through glacial erosion of a thick regolith and resulting exposure of unweathered crystalline bedrock. A one-dimensional ice sheet and bedrock model which includes transport of sediment and ice by subglacial sediment deformation demonstrates that a widespread deforming sediment layer maintains thin ice sheets before the transition which respond linearly to the dominant (23 and 41 kyr) orbital forcing. Progressive removal of the sediment layer eventually causes a transition to thicker ice sheets whose dominant timescale of change (100 kyr) reflects nonlinear deglaciation processes. In model simulations over the last 3 Ma initialized with no ice and a uniform 50 m sediment layer the time series of ice volume and extent agree in several important aspects with the observed records.