A 53 year seasonally resolved oxygen and carbon isotope record from a modem Gibraltar speleothem: Reconstructed drip water and relationship to local precipitation
A 53 year seasonally resolved oxygen and carbon isotope record from a modem Gibraltar speleothem: Reconstructed drip water and relationship to local precipitation
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DOI：
10.1016/j.epsl.2008.01.051
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发表时间：
2008-05-15
影响因子：
5.3
通讯作者：
Frisia, S.
中科院分区：
文献类型：
--
作者：
Mattey, David;Lowry, D.;Frisia, S.
气候代理对测得的温度，降雨量和大气环流模式在次年度分辨率的响应是代理保真度的最终测试，但很少有数据存在显示洞穴气候代理和仪器气候记录之间的对应程度。直布罗陀半岛上的洞穴遗址提供了一个独特的机会，可以利用已知最长的降水同位素和仪器记录来校准洞穴气候代用指标。2004年从新圣迈克尔斯洞穴采集的一个活跃生长的洞穴堆积物由成对的薄层组成，薄层由浅色柱状方解石和深色细晶方解石组成。稳定同位素分析的样品微磨在100亩米的步骤相当于双月的间隔揭示了织物相关的碳同位素，氧同位素和微量元素的年度周期响应洞穴小气候，水文和通风模式的季节性变化。方解石δ C-13值在浅色柱状结构中达到最小值，微量元素行为和洞穴监测的证据表明，这是在pCO最高的洞穴“冬季”条件下生长的（2），而深色微亮方解石，其特征是δ C-13和δ O-18值升高，在低“夏季”pCO（2）条件下生长。滴水三角洲C-13（DIC）在3月至4月达到最小值，此时衰减的三角洲O-18信号成为冬季降水的最具代表性。基于循环计数和C-14炸弹碳峰值位置的年龄模型产生了一个精确定年的洞穴渗漏水的冬季氧同位素代用品，用于与直布罗陀的GNIP和仪器气候记录进行比较。从代表每年冬季降水的滴水中沉积的方解石的三角洲O-18特征可以从季节性分辨记录中得出，并允许重建代表1951-2004年每年冬季降水的三角洲O-18滴水。这些数据显示出令人鼓舞的对应水平（r（2）=0.47）与每年10月至3月的降雨量下降的三角洲O-18，在十年尺度上，重建的冬季滴水的三角洲O-18反映了冬季平均温度的长期变化。(C)2008 Elsevier B. V.保留所有权利。
The response of a climate proxy against measured temperature, rainfall and atmospheric circulation patterns at sub-annual resolution is the ultimate test of proxy fidelity but very few data exist showing the level of correspondence between speleothem climate proxies and the instrumental climate record. Cave sites on the Gibraltar peninsula provide a unique opportunity to calibrate speleothem climate proxies with the longest known available precipitation isotopes and instrumental records. An actively growing speleothem sampled from New St. Michaels Cave in 2004 is composed of paired laminae consisting of light columnar calcite and a darker microsparitic calcite. Stable isotope analysis of samples micromilled in 100 mu m steps at the equivalent of bi-monthly intervals reveals fabric-correlated annual cycles in carbon isotopes, oxygen isotopes and trace elements responding to seasonal changes in cave microclimate, hydrology and ventilation patterns. Calcite delta C-13 values reach a minimum in the light columnar fabric and evidence from trace element behaviour and cave monitoring indicates that this grows under cave 'winter' conditions of highest pCO(2), whereas the dark microsparitic calcite, characterised by elevated delta C-13 and delta O-18 values grows under low 'summer' pCO(2) conditions. Drip water delta C-13(DIC) reaches a minimum in March-April, at which time the attenuated delta O-18 signal becomes most representative of winter precipitation. An age model based on cycle counting and the position of the C-14 bomb carbon spike yields a precisely dated winter oxygen isotope proxy of cave seepage water for comparison with the GNIP and instrumental climate record for Gibraltar. The delta O-18 characteristics of calcite deposited from drip water representing winter precipitation for each year can be derived from the seasonally resolved record and allows reconstruction of the delta O-18 drip water representing winter precipitation for each year from 1951-2004. These data show an encouraging level of correspondence (r(2)=0.47) with the delta O-18 of rainfall falling each year between October and March and on a decadal scale the delta O-18 of reconstructed winter drip water mirrors secular change in mean winter temperatures. (C) 2008 Elsevier B.V. All rights reserved.