North American ice-sheet dynamics and the onset of 100,000-year glacial cycles
North American ice-sheet dynamics and the onset of 100,000-year glacial cycles
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DOI：
10.1038/nature07158
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发表时间：
2008-08-14
期刊：
影响因子：
64.8
通讯作者：
van de Wal, R. S. W.
中科院分区：
文献类型：
--
作者：
Bintanja, R.;van de Wal, R. S. W.
北半球大约 270 万年前 (1) 爆发的主要冰川作用很可能是由上新世晚期的气候变冷引起的 (2,3)。这些冰川作用期间，北半球冰盖相继扩张和后退，叠加在这种长期气候趋势上，并与地球轨道参数的变化有关(4)。与轨道驱动的冰川循环相关的一个有趣的问题是从 41,000 年到 100,000 年的气候循环的转变，这种转变在日照强迫没有明显变化的情况下发生(5)。人们提出了几种假设来解释这种转变，包括和排除冰盖动力学(6-10)。为这个古气候问题找到决定性答案的困难与缺乏足够长的冰盖体积或海平面记录有关。在这里，我们使用综合冰盖模型和简单的海洋温度模型（11）从海洋底栖氧同位素中提取了三百万年相互一致的表面气温、冰量和海平面记录（12）。尽管由于古气候限制的可用性有限，这些记录及其相对阶段受到相当大的不确定性，但结果表明，10万年周期的逐渐出现可归因于合并的北美冰盖承受日照最大值并达到大陆规模大小的能力增强。超大的湿基冰盖可能通过增加基底滑动而快速变薄来响应随后的最大日照量(13,14)，从而启动冰川终止。根据我们对各个冰川期间气温和冰量随时间变化的评估，我们证明了冰动力学和冰-气候相互作用在建立十万年冰川周期中的重要性，其中北美冰盖生长增强和随后冰盖的合并是关键因素。
The onset of major glaciations in the Northern Hemisphere about 2.7 million years ago(1) was most probably induced by climate cooling during the late Pliocene epoch(2,3). These glaciations, during which the Northern Hemisphere ice sheets successively expanded and retreated, are superimposed on this long-term climate trend, and have been linked to variations in the Earth's orbital parameters(4). One intriguing problem associated with orbitally driven glacial cycles is the transition from 41,000-year to 100,000-year climatic cycles that occurred without an apparent change in insolation forcing(5). Several hypotheses have been proposed to explain the transition, both including and excluding ice-sheet dynamics(6-10). Difficulties in finding a conclusive answer to this palaeoclimatic problem are related to the lack of sufficiently long records of ice-sheet volume or sea level. Here we use a comprehensive ice-sheet model and a simple ocean-temperature model(11) to extract three-million-year mutually consistent records of surface air temperature, ice volume and sea level from marine benthic oxygen isotopes(12). Although these records and their relative phasings are subject to considerable uncertainty owing to limited availability of palaeoclimate constraints, the results suggest that the gradual emergence of the 100,000-year cycles can be attributed to the increased ability of the merged North American ice sheets to survive insolation maxima and reach continental-scale size. The oversized, wet-based ice sheet probably responded to the subsequent insolation maximum by rapid thinning through increased basal-sliding(13,14), thereby initiating a glacial termination. Based on our assessment of the temporal changes in air temperature and ice volume during individual glacials, we demonstrate the importance of ice dynamics and ice-climate interactions in establishing the 100,000-year glacial cycles, with enhanced North American ice-sheet growth and the subsequent merging of the ice sheets being key elements.