Delayed build-up of Arctic ice sheets during 400,000-year minima in insolation variability
Delayed build-up of Arctic ice sheets during 400,000-year minima in insolation variability
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40万年日照变化最小值期间北极冰盖的延迟形成
DOI：
10.1038/nature11493
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发表时间：
2012-10-18
期刊：
影响因子：
64.8
通讯作者：
Guo, Zhengtang
中科院分区：
文献类型：
--
作者：
Hao, Qingzhen;Wang, Luo;Guo, Zhengtang
了解北方高纬度地区过去在天文学上与现在间冰期相似的气候变化，可能有助于我们了解未来的气候变化。不幸的是，在北方半球的冰盖变化的长期连续记录是稀缺的，因为记录的底栖18 O含量代表了在两个极地地区的冰量变化的综合信号。然而，北方冰盖的变化影响西伯利亚高压（一个大气压系统），所以东亚冬季风（EAWM）的变化-在中国黄土高原上的风尘沉积物记录-可以作为一个有用的代理北极气候变率的冰芯记录开始之前。在这里，我们提出了一个EAWM代理记录使用粒度变化在两个平行的黄土剖面代表整个中国黄土高原在过去90万年的序列。结果表明，在大约40万年间隔的低离心率和岁差变化期间，EAWM的粒度推断强度在间冰期夏季风活动和成壤作用结束后的2万年内仍然很弱。相反，在大多数其他间冰期结束后，EAWM迅速增加。我们的结论是，对于这两个40万年间冰期，弱EAWM风保持一个温和的，非冰川气候在高纬度北方比预期的更长的时间从传统的黄土和海洋氧同位素记录。在这段时间里，65° N（参考文献）的夏季日照最小值会抑制冰雪的积累，导致西伯利亚高压减弱，从而导致弱的EAWM风。
Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial may help to inform our understanding of future climate change. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic18O content represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)—as recorded in the aeolian dust deposits on the Chinese Loess Plateau—can serve as a useful proxy of Arctic climate variability before the ice-core record begins. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections representative of sequences across the whole of the Chinese Loess Plateau over the past 900,000 years. The results show that during periods of low eccentricity and precessional variability at approximately 400,000-year intervals, the grain-size-inferred intensity of the EAWM remains weak for up to 20,000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for both the 400,000-year interglacials, the weak EAWM winds maintain a mild, non-glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records. During these times, the less-severe summer insolation minima at 65° N (ref. ) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds.