Late Pliocene to early Pleistocene climate dynamics in western North America based on a new pollen record from paleo-Lake Idaho
Late Pliocene to early Pleistocene climate dynamics in western North America based on a new pollen record from paleo-Lake Idaho
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DOI：
10.1007/s12549-020-00460-1
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发表时间：
2021-01
影响因子：
1.4
通讯作者：
Frederik J. Allstädt;A. Koutsodendris;E. Appel;W. Rösler;T. Reichgelt;Stefanie Kaboth‐Bahr;A. Prokopenko;J. Pross
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文献类型：
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作者：
Frederik J. Allstädt;A. Koutsodendris;E. Appel;W. Rösler;T. Reichgelt;Stefanie Kaboth‐Bahr;A. Prokopenko;J. Pross
以高纬度地区冰盖扩张为标志的北半球冰川作用的增强，在~ 2.7 Ma的上新世/更新世过渡时期是晚新近纪气候演化的一个关键时期。迄今为止，由于缺乏连续的、高分辨率的陆地记录，对那段时间北美气候变化的特征及其对植被的影响仍然知之甚少。本文基于国际大陆钻探计划（ICDP）取心活动中获取的美国西蛇河平原古爱达荷湖湖层序的花粉记录，对北美西北部上新世晚期和更新世早期（约2.8-2.4 Ma）的植被动态进行了评估。我们的数据表明，森林生态系统对冰川/间冰期变率的敏感响应是以轨道倾角为速度的，并且还强调了在更新世第一次强冰期（即海洋同位素阶段100）可能发生的明显的草原元素扩张。孢粉资料记录了约2.6 Ma时的主要森林生物群系变化，其标志是由针叶林为主的森林转变为开放的混交林。基于花粉的定量气候估计表明，这种森林重组与上新世晚期至更新世早期降水的增加有关。我们将这种转变归因于从亚北极太平洋到北美的水汽输送增强，从而证实了海洋环流变化有助于北半球冰川作用增强的假设。
Marked by the expansion of ice sheets in the high latitudes, the intensification of Northern Hemisphere glaciation across the Plio/Pleistocene transition at ~ 2.7 Ma represents a critical interval of late Neogene climate evolution. To date, the characteristics of climate change in North America during that time and its imprint on vegetation has remained poorly constrained because of the lack of continuous, highly resolved terrestrial records. We here assess the vegetation dynamics in northwestern North America during the late Pliocene and early Pleistocene (c. 2.8–2.4 Ma) based on a pollen record from a lacustrine sequence from paleo-Lake Idaho, western Snake River Plain (USA) that has been retrieved within the framework of an International Continental Drilling Program (ICDP) coring campaign. Our data indicate a sensitive response of forest ecosystems to glacial/interglacial variability paced by orbital obliquity across the study interval, and also highlight a distinct expansion of steppic elements that likely occurs during the first strong glacial of the Pleistocene, i.e. Marine Isotope Stage 100. The pollen data document a major forest biome change at ~ 2.6 Ma that is marked by the replacement of conifer-dominated forests by open mixed forests. Quantitative pollen-based climate estimates suggest that this forest reorganisation was associated with an increase in precipitation from the late Pliocene to the early Pleistocene. We attribute this shift to an enhanced moisture transport from the subarctic Pacific Ocean to North America, confirming the hypothesis that ocean-circulation changes were instrumental in the intensification of Northern Hemisphere glaciation.