Rapidly receding Arctic Canada glaciers revealing landscapes continuously ice-covered for more than 40,000 years
Rapidly receding Arctic Canada glaciers revealing landscapes continuously ice-covered for more than 40,000 years
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加拿大北极地区的冰川迅速消退，显露出四万多年来持续被冰雪覆盖的景观
DOI：
10.1038/s41467-019-08307-w
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发表时间：
2019
影响因子：
16.6
通讯作者：
R. Anderson
中科院分区：
文献类型：
--
作者：
S. Pendleton;G. Miller;N. Lifton;S. Lehman;J. Southon;S. Crump;R. Anderson
由于极地地区特有的强烈正反馈，北极气温的上升速度快于北方半球的平均水平。然而，最近北极变暖的程度是前所未有的，仍然存在争议。在加拿大北极地区，由于冰盖的消退，埋葬在生长位置的植物的年龄有助于解决这个问题，将最近的条件放在一个多千年的背景下。在这里，我们表明，在加拿大北极地区30个冰盖的边缘收集的植物的全新世前放射性碳年代表明，这些地方连续被冰覆盖超过40 kyr，但现在没有冰。我们使用原位14 C库存从9个地点的岩石，探讨在温暖的全新世早期短暂曝光的可能性。模拟原位14 C的演变证实，全新世暴露是不可能的，但在所有的网站之一。从格陵兰冰芯的温度记录来看，我们的结果表明，过去世纪的夏季温暖超过了115,000年来的任何世纪。不断缩小的加拿大北极冰盖揭示了保存完好的景观，其中包含过去冰川活动的记录。在这里，作者表明，这些景观中植物的14 C年龄和宇宙成因的14 C浓度表明，最近暴露的景观已经连续被冰覆盖了超过40，000年。
Arctic temperatures are increasing faster than the Northern Hemisphere average due to strong positive feedbacks unique to polar regions. However, the degree to which recent Arctic warming is unprecedented remains debated. Ages of entombed plants in growth position preserved by now receding ice caps in Arctic Canada help to address this issue by placing recent conditions in a multi-millennial context. Here we show that pre-Holocene radiocarbon dates on plants collected at the margins of 30 ice caps in Arctic Canada suggest those locations were continuously ice covered for > 40 kyr, but are now ice-free. We use in situ 14C inventories in rocks from nine locations to explore the possibility of brief exposure during the warm early Holocene. Modeling the evolution of in situ 14C confirms that Holocene exposure is unlikely at all but one of the sites. Viewed in the context of temperature records from Greenland ice cores, our results suggest that summer warmth of the past century exceeds now any century in ~115,000 years. Shrinking Arctic Canada ice caps are revealing preserved landscapes containing a record of past glacier activity. Here the authors show that 14C ages of plants and cosmogenic 14C concentrations from these landscapes indicate that recently exposed landscapes have been continuously ice covered for > 40,000 years.