Cold-season temperatures in the European Alps during the past millennium: variability, seasonality and recent trends
Cold-season temperatures in the European Alps during the past millennium: variability, seasonality and recent trends
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DOI：
10.1016/j.quascirev.2013.10.007
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发表时间：
2013-12-15
影响因子：
4
通讯作者：
Grosjean, M.
中科院分区：
文献类型：
--
作者：
de Jong, R.;Kamenik, C.;Grosjean, M.
本研究提出了一个基于代理的，定量重建冷季（平均10月至5月，Toct-May）几乎覆盖整个上千年的气温（公元1060-2003年，一些间断）。重建是基于瑞士阿尔卑斯山东部高阿尔卑斯湖Silvaplana的纹状沉积物中的亚化石金藻气孔囊遗骸（北纬46度27分，西经9度48分，海平面高度1791米）。先前的研究已经通过与气象数据的比较证明了这一代理的可靠性。冷季气温，因此，可以重建定量，在一个高分辨率（5年），并具有较高的时间精度。空间相关性分析表明，重建反映了高阿尔卑斯地区和中欧和西欧大部分地区的冷季气候变化。冷季温度的特点是在公元1440年之前的千年的第一部分相对稳定（5年平均值的2 σ = 0.7 ℃），之后的TOC-May高度可变（AD 1440-1900，5年平均值的2 σ = 1.3 ℃）。最近几十年（公元1991年至今）是异常温暖的背景下，上一个千年（超过2 σ范围的平均十年TOC-May），但这种温暖是不是前所未有的。最冷的十年发生在公元1510-1520年和公元1880-1890年。极端温暖和寒冷的几十年的时间一般是在很好的协议与文件数据代表瑞士和中欧lowlands.The从相对稳定的过渡到高度可变的TOC-May正好与大的变化，在北大西洋地区的大气环流模式。重建的冷季温度的北大西洋涛动指数（NAO）在过去的1000年的比较表明，相对稳定和温暖的条件下，在研究现场，直到公元1440年与持续的积极模式的NAO相吻合。我们建议，在AD 1440年左右的大TOC-May变化的过渡与随后没有这种持续的纬向流型有关，这将使其他气候驱动因素在研究区域获得重要性。从AD 1440-1900年，重建的TOC-May的西伯利亚高压重建的气压的相似性表明，在西风气流减弱的时期，大陆反气旋系统对阿尔卑斯山冷季气候参数的影响相对较强。一个更大陆型的大气环流，因此似乎是小冰期在Europe.Comparison的Toc-May夏季温度重建从同一个研究站点的特点表明，正如预期的那样，夏季和冷季温度的趋势和变化完全不同，在整个近1000年。然而，自公元1980年以来，夏季和寒冷季节的气温同时出现了强劲的增长，这在上个千年的背景下是前所未有的。我们认为，最近的趋势最可能的解释是人为温室气体（GHG）强迫。(C)2013爱思唯尔有限公司保留所有权利。
This study presents a proxy-based, quantitative reconstruction of cold-season (mean October to May, Toct-May) air temperatures covering nearly the entire last millennium (AD 1060-2003, some hiatuses).The reconstruction was based on subfossil chrysophyte stomatocyst remains in the varved sediments of high-Alpine Lake Silvaplana, eastern Swiss Alps (46 degrees 27'N, 9 degrees 48'W, 1791 m a.s.I.). Previous studies have demonstrated the reliability of this proxy by comparison to meteorological data. Cold-season air temperatures could therefore be reconstructed quantitatively, at a high resolution (5-yr) and with high chronological accuracy. Spatial correlation analysis suggests that the reconstruction reflects cold season climate variability over the high- Alpine region and substantial parts of central and western Europe.Cold-season temperatures were characterized by a relatively stable first part of the millennium until AD 1440 (2 sigma of 5-yr mean values = 0.7 degrees C) and highly variable TOct-May after that (AD 1440-1900, 2 sigma of 5-yr mean values = 1.3 degrees C). Recent decades (AD, 1991-present) were unusually warm in the context of the last millennium (exceeding the 2 sigma-range of the mean decadal TOct-May) but this warmth was not unprecedented. The coolest decades occurred from AD 1510-1520 and AD 1880-1890. The timing of extremely warm and cold decades is generally in good agreement with documentary data representing Switzerland and central European lowlands.The transition from relatively stable to highly variable TOct-May coincided with large changes in atmospheric circulation patterns in the North Atlantic region. Comparison of reconstructed cold season temperatures to the North Atlantic Oscillation index (NAO) during the past 1000 years showed that the relatively stable and warm conditions at the study site until AD 1440 coincided with a persistent positive mode of the NAO. We propose that the transition to large TOct-May variability around AD 1440 was linked to the subsequent absence of this persistent zonal flow pattern, which would allow other climatic drivers to gain importance in the study area. From AD 1440-1900, the similarity of reconstructed TOct-May to reconstructed air pressure in the Siberian High suggests a relatively strong influence of continental anticyclonic systems on Alpine cold season climate parameters during periods when westerly airflow was subdued. A more continental type of atmospheric circulation thus seems to be characteristic for the Little Ice Age in Europe.Comparison of Toct-May to summer temperature reconstructions from the same study site shows that, as expected, summer and cold season temperature trends and variability differed completely throughout nearly the entire last 1000 years. Since AD 1980, however, summer and cold season temperatures show a simultaneous, strong increase, which is unprecedented in the context of the last millennium. We suggest that the most likely explanation for this recent trend is anthropogenic greenhouse gas (GHG) forcing. (C) 2013 Elsevier Ltd. All rights reserved.