A stable isotope record of Holocene precipitation dynamics in the Baltic region from Lake Nuudsaku, Estonia
A stable isotope record of Holocene precipitation dynamics in the Baltic region from Lake Nuudsaku, Estonia
复制标题
爱沙尼亚努德萨库湖波罗的海地区全新世降水动态的稳定同位素记录
DOI：
10.1016/j.quascirev.2017.09.013
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发表时间：
2017
影响因子：
4
通讯作者：
D. Nelson
中科院分区：
文献类型：
--
作者：
N. Stansell;E. Klein;M. Finkenbinder;Carolyn S. Fortney;J. Dodd;J. Terasmaa;D. Nelson
波罗的海区域过去水文气候变化的长期视角为评估北半球温度变化和不断变化的海洋-大气相互作用对北欧气候的潜在影响提供了重要背景。Nuudsaku湖是爱沙尼亚中南部的一个开阔盆地湖泊，季节性溢流由活跃的泉水和地下水提供。区域湖泊、河流、湿地和降水地表水的稳定同位素分析表明，努德萨库湖水的δ18O值与入湖大气降水的同位素组成基本一致。来自努达萨库湖的细粒(~lt；63μm)内生CaCO_3(δ180方解石)样品的同位素组成在∼14~-9‰(∼9400年)之间变化。根据敏感性测试，我们将努德萨库湖的δ180钙化变化解释为大气输入的记录；主要反映了降水季节性的变化，温度变化是次要影响。δ180℃记录表明，距今9400历年(∼Yr BP)的全新世早期以冷季(11月至4月)降水比例高、气温较低为特征，随后冷季降水减弱、气温升高，直到∼8200日历年BP。中全新世(8200-4200年前)可能是冷季降水总体减少、气温升高和/或暖季(5月至10月)降水增加的时期。晚全新世在∼4200ocalyr BP的转变通常标志着向更低的δ180calcivales的转变，我们认为这在很大程度上是冷季降水量增加的结果。紧随其后的是在∼3600卡·年BP之后，降水量和温度开始发生更多变化，这在过去的∼2600年期间让位于变化较小的条件。中世纪气候异常(Mca)以接近全新世和现代平均值的δ180钙化值为标志。小冰期(LIA)的特点是δ180摄氏度较低，这表明气温比现在更低，寒冷的季节条件比现在更潮湿。来自Nuudsaku湖的替代证据进一步表明，波罗的海区域百年至千年尺度的水文气候变化可能与北大西洋海洋-大气环流动态的变化有关。
A long-term perspective of past hydroclimate variability for the Baltic region provides important context for evaluating the potential impacts of Northern Hemisphere temperature changes and shifting ocean-atmospheric interactions on northern European climate. Lake Nuudsaku is an open-basin lake in south-central Estonia with seasonal overflow fed by active springs and groundwater. Stable isotope analyses of surface water samples from regional lakes, rivers, wetlands, and precipitation indicate that Lake Nuudsaku water δ18O values are consistent with the isotopic composition of inflowing meteoric water. The isotopic composition of fine-grained (<63 μm) endogenic CaCO3(δ18Ocalcite) samples from Lake Nuudsaku vary between ∼14 to -9‰ (VPBD) over the last ∼9400 years. Based on sensitivity tests, we interpret the δ18Ocalcitevariations from Lake Nuudsaku as a record of meteoric inputs; principally reflecting variations in the seasonality of precipitation, with temperature changes as a secondary influence. The δ18Ocalciterecord indicates the early Holocene at ∼9400 calendar years before present (cal yr BP) was characterized by a high proportion of cold season (November through April) precipitation and lower temperatures, followed by waning cold season precipitation and higher temperatures until ∼8200 cal yr BP. The middle Holocene (8200–4200 cal yr BP) was likely a period of overall reduced cold season precipitation and higher temperatures, and/or increased warm season (May through October) precipitation. The late Holocene transition at ∼4200 cal yr BP generally marks a shift to lower δ18Ocalcitevalues that we interpret largely the result of increased cold season precipitation amounts. This was followed by the onset of more variable precipitation amounts and temperatures after ∼3600 cal yr BP, which gave way to less variable conditions during the last ∼2600 years. The Medieval Climate Anomaly (MCA) is marked by δ18Ocalcitevalues that are near the Holocene and present-day averages. The period spanning the Little Ice Age (LIA) is marked by low δ18Ocalcitevalues, suggesting temperatures were lower and cold season conditions were wetter than present-day. Proxy evidence from Lake Nuudsaku further indicates that centennial to millennial-scale hydroclimate shifts in the Baltic region were likely associated with changes in North Atlantic ocean-atmospheric circulation dynamics.