The Marine Isotope Stage 12 pollen record from Lake Ohrid (SE Europe): Investigating short-term climate change under extreme glacial conditions
The Marine Isotope Stage 12 pollen record from Lake Ohrid (SE Europe): Investigating short-term climate change under extreme glacial conditions
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DOI：
10.1016/j.quascirev.2019.105873
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发表时间：
2019-10-01
影响因子：
4
通讯作者：
Pross, Joerg
中科院分区：
文献类型：
--
作者：
Koutsodendris, Andreas;Kousis, Ilias;Pross, Joerg
以北半球大陆冰盖最大扩张为特征的海洋同位素第12期(类似于现在的478-424ka)是第四纪最强烈的冰川之一。由于目前在管理信息系统12上可获得的信息主要来自海洋记录，这种极端冰川对陆地领域--特别是陆地生态系统--的影响仍然很少受到限制。在这里，我们呈现了一个新的百年尺度分辨率的花粉记录，来自奥赫里德湖(欧洲东南部的巴尔干半岛)，并增加了基于花粉的定量温度和降水估计。我们的数据集，从488年到420ka，显示在MIS12期间，奥赫里德湖周围的森林覆盖率大幅下降；这种下降与冬季和年平均温度(以及夏季温度较小的程度)以及平均年降水量的逐渐降低有关。在这种长期发展的基础上，区域森林覆盖率的突然变化表明了一种明显的千年尺度的气候变化，与上一次冰川的年际和盛年事件有很大的相似之处。这种变异性表现为在MIS12c和12b亚阶段最古老的部分(即从类似于477 ka到类似于448 ka)期间，奥赫里德湖周围反复出现高幅度的森林扩张和收缩。森林振荡可以与之前记录的北大西洋地表水变化和冰筏碎屑沉积事件相关联。这一模式表明，在千年时间尺度上，欧洲东南部气候强迫树种数量变化与12c和部分12b期间大西洋经向海洋环流的变化之间存在耦合。相比之下，MIS12b和MIS12a的最年轻部分(即类似于448到424 ka)在奥赫里德湖周围缺乏高幅度的森林扩张和收缩。与MIS12重建的海平面对比表明，当海平面比现在低30~100m时，奥赫里德湖千年尺度的植被变化最强，而当海平面比现在低100m时，奥赫里德湖的千年尺度植被变化不明显。(C)2019爱思唯尔有限公司。保留所有权利。
Characterised by a maximum expansion of continental ice sheets in the Northern Hemisphere, Marine Isotope Stage (MIS) 12 (similar to 478-424 ka before present) was one of the strongest glacials of the Quaternary. Because the information currently available on MIS 12 is predominantly derived from marine records, the imprint of this extreme glaciation on the terrestrial realm - and notably on terrestrial ecosystems - has remained poorly constrained. Here we present a new, centennial-scale-resolution pollen record from Lake Ohrid (Balkan Peninsula, SE Europe) augmented by pollen-based quantitative temperature and precipitation estimates. Our dataset, which spans the period from 488 to 420 ka, shows that the forest cover around Lake Ohrid decreased substantially over the course of MIS 12; this decrease was associated with a gradual lowering of winter and mean annual temperatures (and to a lesser extent of summer temperatures) as well as mean annual precipitation. Superimposed on this long-term development, abrupt changes in regional forest cover indicate a pronounced millennial-scale climate variability that bears strong resemblance to the interstadial and stadial events of the Last Glacial. This variability is expressed by repeated high-amplitude forest expansions and contractions around Lake Ohrid during MIS 12c and the oldest part of 12b substage (i.e., from similar to 477 to similar to 448 ka). The forest oscillations can be correlated to previously documented episodes of surface-water variability and ice-rafted debris deposition in the North Atlantic. This pattern suggests a coupling between the climatically forced treepopulation changes in SE Europe and the variability of the Atlantic Meridional Ocean Circulation during MIS 12c and partially 12b on millennial timescales. In contrast, the youngest part of MIS 12b and MIS 12a (i.e., from similar to 448 to 424 ka) lack high-amplitude forest expansions and contractions around Lake Ohrid. Comparison with sea-level reconstructions for MIS 12 suggests that millennial-scale vegetation variability in Lake Ohrid was strongest when sea level was between 30 and 100 m lower than today, whereas it was absent when sea level was lower than 100 m relative to the present. (C) 2019 Elsevier Ltd. All rights reserved.