Relative humidity recorded in tree rings: A study along a precipitation gradient in the Olympic Mountains, Washington, USA
Relative humidity recorded in tree rings: A study along a precipitation gradient in the Olympic Mountains, Washington, USA
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DOI：
10.1016/j.gca.2004.08.013
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发表时间：
2005-02
影响因子：
5
通讯作者：
Y. Shu;Xiahong Feng;C. Gazis;Doug H. Anderson;A. Faiia;K. Tang;G. Ettl
中科院分区：
文献类型：
--
作者：
Y. Shu;Xiahong Feng;C. Gazis;Doug H. Anderson;A. Faiia;K. Tang;G. Ettl
湿度是控制气候能量平衡的基本变量之一，因此它的重建是古气候研究的一个重要方面。本文报道了美国华盛顿奥林匹克山树木年轮纤维素沿着降水梯度的氧和氢同位素组成的研究，以检验相对湿度是否以及如何记录在纤维素中。根据本文所建立的物理模型，在研究点间平均相对湿度无系统变化和树木间无生理差异的情况下，纤维素δD与δ 18 O的关系应与源水δD与δ 18 O的关系具有相同的斜率（当地大气降水为1.88）。然而，我们对纤维素的同位素分析得出的斜率为17.4，明显大于当地大气水线的斜率。我们表明，要产生这样的斜率，相对湿度和源水中的δD和δ 18 O之间的正协变是需要跨越降水梯度。研究表明，树木年轮中δD与δ18O的关系可以作为重建古湿度的有用工具。
Humidity is one of the fundamental variables controlling the energy balance of the climate, and thus its reconstruction represents a significant aspect of paleoclimate studies. We here report a study of oxygen and hydrogen isotopic compositions of tree-ring cellulose along a precipitation gradient in the Olympic Mountains of Washington, USA, to examine whether and how the relative humidity is recorded in the cellulose. According to the physically-based model described in this paper, the relationship between δD and δ18O of cellulose should have the same slope as that in the relationship between δD and δ18O in the source water (∼8.8 for the local meteoric water) if there is no systematic variation in the mean relative humidity among study sites and no physiologic differences among trees. However, our isotopic analyses of cellulose yielded a slope of 17.4, significantly greater than the slope of the Local Meteoric Water Line. We show that to produce such a slope, a positive covariation between the relative humidity and the δD and δ18O in the source water is required across the precipitation gradient. This work suggests that the δD vs. δ18O relationship in tree rings can be a useful tool for paleohumidity reconstruction.