Stable source of Holocene spring precipitation recorded in leaf wax hydrogen-isotope ratios from two New York lakes
Stable source of Holocene spring precipitation recorded in leaf wax hydrogen-isotope ratios from two New York lakes
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DOI：
10.1016/j.quascirev.2020.106357
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发表时间：
2020-07
影响因子：
4
通讯作者：
Anna K. Schartman;A. Diefendorf;T. Lowell;E. Freimuth;A. Stewart;J. Landis;Benjamin R. Bates
中科院分区：
文献类型：
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作者：
Anna K. Schartman;A. Diefendorf;T. Lowell;E. Freimuth;A. Stewart;J. Landis;Benjamin R. Bates
天气大气环流模式的变化被认为在建立千年尺度的气候周期在晚冰期和全新世结束时发挥作用。在美国东北部，多代理证据记录了这段时间内有效湿度和温度的波动，但限制大气过程和这些气候制度之间的关系并不简单。由于沉积的陆地叶蜡的氢同位素比值可以反映降水δD，这些长链烃化合物是一个很好的工具，研究水分来源。在这里，我们提出了湖泊沉积物和叶蜡的碳和氢同位素记录，跨越过去114.0万年的心湖和驼鹿池在阿迪朗达克山脉（ADK），纽约。盆地形成后湖泊的高初始生产力反映在低的C：N比（<15）和相对较高的短链正构烷烃（n-C17、n-C19和n-C21）与长链正构烷烃（n-C27、n-C29和n-C31）的浓度比。全新世记录的特征是低体积和正构烷烃δ 13 C（分别为δ-28 ‰和δ-31 ‰），高ACL 25 -35（δ-28 ‰），以及高相对浓度的长链正构烷烃同系物，表明这一时期的有机质主要来自陆地。两个湖盆的n-C29正构烷烃氢同位素比值在全新世仅为1.20 ‰，重建的降水δD（δDprecip）与现代模拟的春季降水δD（δDprecip）吻合较好。这表明，在整个记录时间内，ADK春季降水的来源可能没有重大变化。
Changes in synoptic atmospheric circulation patterns are thought to play a role in establishing millennial scale climate periods during the end of the late glacial and the Holocene. In the northeastern United States, multi-proxy evidence documents fluctuations in effective moisture and temperatures for this time period, but constraining the relationship between atmospheric processes and these climate regimes is not straightforward. Because the hydrogen-isotope ratios of sedimentary terrestrial leaf waxes can reflect precipitation δD, these long-chain hydrocarbon compounds are an excellent tool to investigate moisture sourcing. Here we present lake sediment and leaf wax carbon- and hydrogen-isotope records that span the past ∼14.0 thousand years from Heart Lake and Moose Pond in the Adirondack Mountains (ADK), New York. High initial lake productivity after basin inception is reflected in low C:N ratios (<15), and higher relative short chainn-alkane (n-C17,n-C19, andn-C21) to long chainn-alkane (n-C27,n-C29andn-C31) concentration ratios. The Holocene record is characterized by low bulk andn-alkane δ13C (∼ −28‰, ∼ −31‰, respectively), high ACL25-35(∼28), and high relative concentrations of long chainn-alkane homologues, indicating a dominantly terrestrial source of organic matter for this time period. Hydrogen-isotope ratios ofn-C29n-alkane from both lake basins range only ∼20‰ through the Holocene and reconstructed precipitation δD (δDprecip) from both basins is in good agreement with that of modern modeled spring precipitation. This suggests there may have been no major changes in the sourcing of spring precipitation for the ADK throughout the time of record.