Earliest Eocene cold period and polar amplification - Insights from δ2H values of lignin methoxyl groups of mummified wood
Earliest Eocene cold period and polar amplification - Insights from δ2H values of lignin methoxyl groups of mummified wood
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DOI：
10.1016/j.palaeo.2018.05.049
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发表时间：
2018-09-15
影响因子：
3
通讯作者：
Keppler, Frank
中科院分区：
文献类型：
--
作者：
Anhaeuser, Tobias;Hook, Benjamin A.;Keppler, Frank
三个保存完好的木乃伊木标本已被挖掘出三个最早的始新世（类似于55.5，55.2和53.3马）金伯利岩管在亚北极西北地区，加拿大（类似于64度N）。每个标本包含几十年的长度树轮系列，并允许测量稳定的氢同位素比（δ H-2值）的木质素甲氧基（常用的纤维素在很大程度上降解）。我们使用这些三角洲H-2的签名重建三个代表性的三角洲H-2值的当地降水，通过应用校准的同位素分馏，调查深时古气候。我们的重建表明前所未有的低价值亚北极早始新世，然而，显示在类似的2.2百万年的增加趋势，从206 - 17，202 - 17至168 - 17千分之一。这些值被解释沿着与其他北极，亚北极和中纬度的代理记录的时间段表明，在总的一段时间内，低稳定的氢和氧同位素比值的降水（发病55.7和54.9马和恢复在53.3 +/- 0.6马），这被认为是主要由大陆冷期。我们的亚北极重建指出，这一寒冷时期的幅度增加，北极的地表气温变化超过全球趋势（响应气候强迫）。在试图量化的极性放大幅度，我们估计北极的温度变化，结合我们的三角洲H-2的结果与始新世早期的温度和稳定的水同位素之间的现有关系。将北极温度变化与全球估计值进行比较，
Three well-preserved mummified wood specimens have been excavated from three earliest Eocene (similar to 55.5, 55.2 and 53.3 Ma) kimberlite pipes in the subarctic Northwest Territories, Canada (similar to 64 degrees N). Each specimen contained multi-decadal length tree-ring series and allowed measurements of stable hydrogen isotope ratios (delta H-2 values) of the lignin methoxyl groups (commonly used cellulose was largely degraded). We used these delta H-2 signatures for the reconstruction of three representative delta H-2 values of the local precipitation by applying calibrated isotope fractionations to investigate deep-time paleoclimatology. Our reconstructions indicate unprecedented low values for the subarctic early Eocene which, however, show within similar to 2.2 Myr an increasing trend from 206 17, 202 17 to 168 17 parts per thousand. These values were interpreted along with other Arctic, subarctic and mid-latitudinal proxy records of that time period indicating in total a period of low stable hydrogen and oxygen isotope ratios in precipitation (onset between 55.7 and 54.9 Ma and a recovery at 53.3 +/- 0.6 Ma) which is assumed to have been primarily caused by a continental cold period. An increased magnitude of this cold period was noted for our subarctic reconstructions pointing to a polar amplification where surface air temperature changes in the Arctic exceed the global trend (in response to climate forcing). In an attempt to quantify the polar amplification magnitude we estimated Arctic temperature changes using our delta H-2 results in combination with existing relationships between early Eocene temperatures and stable water isotopes. Comparing the Arctic temperature change with a global estimation proposes a polar amplification of magnitude