Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium
Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium
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DOI：
10.5194/cp-14-21-2018
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发表时间：
2018-01-10
影响因子：
4.3
通讯作者：
Mayewski, Paul
中科院分区：
文献类型：
--
作者：
Bohleber, Pascal;Erhardt, Tobias;Mayewski, Paul
在欧洲阿尔卑斯山的冰芯钻探地点中，Colle Gnifetti (CG) 是唯一一个提供至少 1000 年前气候记录的非温带冰川。这种独特的长期档案是由于风蚀和每年层层快速变薄导致的净积累量极低的结果。然而，CG时间序列的充分利用受到了相当大的年代测定不确定性和积雪保存的季节性夏季偏差的阻碍。使用 2013 年钻取的新岩心，我们首次在 CG 上扩展了过去 1000 年来的年度层数计数，并对放射性碳测年得出的年龄范围添加了额外的限制。基于这种改进的年龄尺度，并使用邻近冰芯的多核方法，我们探索了稳定水同位素的时间序列以及代表 Ca2+ 和不溶性颗粒的矿物尘埃。此外，在我们最新的冰芯中，我们还面临着基于重心处高且潜在的非稳态同位素/温度敏感性的稳定同位素变异性定量使用的已知限制。 Ca2+ 的年代际趋势显示与仪器温度基本一致，并在此进行探索，作为基于同位素的温度重建的潜在位点特定补充。观察到的温度和 Ca2+ 趋势之间的耦合可能是由于保雪效应以及与温暖的气温同时发生的富含灰尘的气团的平流造成的。我们发现，如果根据仪器数据进行校准，基于 Ca2+ 的温度重建与最新的基于代理的夏季温度重建非常一致，包括“小冰河时代”寒冷时期以及中世纪气候异常。公元 1100 年至 1200 年左右的中世纪气候时期，沙尘事件的发生明显增多，这可能是由于地中海经向气流和/或干燥条件的相对增加造成的。
Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a "Little Ice Age" cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100-1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.