Early Holocene cold snaps and their expression in the moraine record of the eastern European Alps
Early Holocene cold snaps and their expression in the moraine record of the eastern European Alps
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DOI：
10.5194/cp-17-2451-2021
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发表时间：
2021-12-02
影响因子：
4.3
通讯作者：
Fiebig, Markus
中科院分区：
文献类型：
--
作者：
Braumann, Sandra M.;Schaefer, Joerg M.;Fiebig, Markus
冰川在其地质和地貌记录中保存了气候变化，这使它们成为气候重建的主要候选者。调查过去几千年的冰川气候系统尤其重要，因为全新世自然气候变化的幅度和频率提供了评估现代人类引起的气候变化的气候背景。第二，从末次冰期到当前间冰期的过渡期，在变暖过程中的气候系统的重要见解，这是特别感兴趣的持续的气候changes.Evidence稳定的冰缘位置，记录冷却在过去12 kyr保存在两个冰川山谷的Silvretta地块在东欧阿尔卑斯山，Jamtal（JAM）和Laraintal（LAR）。我们映射和日期的冰碛在这些集水区，包括历史的山脊，使用铍-10表面暴露测年（Be-10 SED）技术和相关冰碛形成间隔与气候代用记录，以评估这些冷相的空间和时间尺度。新的地质年代学表明，冰碛的形成在全新世早期（EH），约。11.0± 0.7ka（n = 19）。巨石年龄沿着历史冰碛（n +/- 6）建议至少有两个冰川前进在小冰期（LIA;约。公元1250-1850年）公元1300年左右和世纪后半叶。一个更早的推进到相同的位置可能发生在公元500年左右。Jamtal和Laraintal冰碛年表提供的证据表明，千年尺度的EH变暖是由百年尺度的冷却叠加。EH冰碛形成的时间与当地和区域古代理记录中确定的短暂温度下降相吻合，最突出的是与北半球前振荡（PBO），并与欧洲阿尔卑斯山和北极地区其他流域的冰碛沉积相一致。这种一致性表明，降温超出了当地的范围，因此是区域甚至半球气候的驱动因素。淡水输入来源于Laurentide冰盖（LIS），改变了北大西洋的环流模式，是一个合理的解释EH冷却和冰碛形成在北欧地区和欧洲。
Glaciers preserve climate variations in their geological and geomorphological records, which makes them prime candidates for climate reconstructions. Investigating the glacier-climate system over the past millennia is particularly relevant first because the amplitude and frequency of natural climate variability during the Holocene provides the climatic context against which modern, human-induced climate change must be assessed. Second, the transition from the last glacial to the current interglacial promises important insights into the climate system during warming, which is of particular interest with respect to ongoing climate change.Evidence of stable ice margin positions that record cooling during the past 12 kyr are preserved in two glaciated valleys of the Silvretta Massif in the eastern European Alps, the Jamtal (JAM) and the Laraintal (LAR). We mapped and dated moraines in these catchments including historical ridges using beryllium-10 surface exposure dating (Be-10 SED) techniques and correlate resulting moraine formation intervals with climate proxy records to evaluate the spatial and temporal scale of these cold phases. The new geochronologies indicate the formation of moraines during the early Holocene (EH), ca. 11.0 +/- 0.7 ka (n = 19). Boulder ages along historical moraines (n +/- 6) suggest at least two glacier advances during the Little Ice Age (LIA; ca. 1250-1850 CE) around 1300 CE and in the second half of the 18th century. An earlier advance to the same position may have occurred around 500 CE.The Jamtal and Laraintal moraine chronologies provide evidence that millennial-scale EH warming was superim-posed by centennial-scale cooling. The timing of EH moraine formation coincides with brief temperature drops identified in local and regional paleoproxy records, most prominently with the Preboreal Oscillation (PBO) and is consistent with moraine deposition in other catchments in the European Alps and in the Arctic region. This consistency points to cooling beyond the local scale and therefore a regional or even hemispheric climate driver. Freshwater input sourced from the Laurentide Ice Sheet (LIS), which changed circulation patterns in the North Atlantic, is a plausible explanation for EH cooling and moraine formation in the Nordic region and in Europe.