Deuterium excess in recent Antarctic snow
Deuterium excess in recent Antarctic snow
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DOI：
10.1029/90jd02232
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发表时间：
1991-03
影响因子：
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通讯作者：
J. Petit;J. White;N. Young;J. Jouzel;Y. Korotkevich
中科院分区：
文献类型：
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作者：
J. Petit;J. White;N. Young;J. Jouzel;Y. Korotkevich
给出了南极中部和东部地表积雪中的氘过量(d=δD-8*δ18O)值。样本主要来自苏联、法国和澳大利亚的横断面。从沿海地区到冰盖上的高海拔地区，d值显示出很大的变化。从沿海到海拔2500m，d值在3~6‰范围内相对恒定，在高海拔地区，d值在东方站和高原站稳定增加到16~18‰。使用δ和Merlivat开发的降水中同位素的动力学瑞利模型，将数据模拟为d与Jouzel和Merlivat的D。该模型考虑了蒸发到海洋上空不饱和空气中的动力学分馏以及在<；−10°C云中形成雪的过程中的动力学分馏，在那里水蒸气相对于雪过饱和。D对δD的总体模式可以很好地符合过饱和度函数，该过饱和度函数随温度的降低而线性增加，并预测了合理的过饱和度。用不同的过饱和函数测试了来自20°~60°S的水蒸气。这些数据只能与S 30°-40°之间的水汽进行拟合，表明这些纬度是南极降雪的主要水汽来源。极地雪的中纬度水汽来源的结论与约翰森及其同事对格陵兰雪的d和δ18O季节周期的分析一致。该模式还用从S 30°到南极海岸的所有纬度同时产生的水汽进行了测试。从50°以南的纬度蒸发了高达20%的水汽，从60°以南的纬度蒸发了5%的水汽，这与海岸附近偶尔观察到的低d值是一致的。沿海和近岸(海拔2000米)降雪的“局部水分”效应的结论支持了Saigne和Legrand通过分析南极雪中的甲烷磺酸得出的类似结论。最后，在降水过程中，海洋表面温度的变化和海洋湿度的变化对南极雪观测到的d值的影响得到了很大的修正。因此，冰芯中d值的解释应在降水模型的背景下进行。
Deuterium excess (d = δD - 8 * δ18O) values in surface snow are presented for central and east Antarctica. The samples are primarily from Soviet, French, and Australian traverses. The d values exhibit a large change going from coastal sites to high-altitude sites on the ice sheet. The d values are relatively constant at 3 to 6‰ from the coast to an altitude of 2500 m, and at higher elevations d increases steadily to values of 16 to 18‰ at Vostok and Plateau Station. The data is modeled as d versus δD using the kinetic Rayleigh model for isotopes in precipitation developed by Jouzel and Merlivat. The model accounts for kinetic fractionation during evaporation into undersaturated air over the ocean and during snow formation in <−10°C clouds where vapor is supersaturated with respect to snow. The overall pattern of d versus δD can be fit well with a supersaturation function which increases linearly with decreasing temperature and which predicts reasonable values of the supersaturation. Vapor originating from 20° to 60°S was tested with different supersaturation functions. The data could only be fit with moisture originating from 30° to 40°S, indicating that these latitudes are the main source of vapor for snow falling in Antarctica. The conclusion of a mid-latitude vapor source for polar snow agrees with the analysis of d and δ18O seasonal cycles in Greenland snow performed by Johnsen and coworkers. The model was also tested with moisture simultaneously originating from all latitudes from 30°S to the Antarctic coast. The addition of up to 20% of moisture evaporated from latitudes south of 50°, and 5% from latitudes south of 60°, is compatible with low d values occasionally observed in snow near the coast. The conclusion of a “local moisture” effect for coastal and near coastal (<2000 m elevation) snowfall supports a similar conclusion by Saigne and Legrand from their analysis of methanesulphonic acid in Antarctic snow. Finally, the effects of changes in the sea surface temperature and changes in oceanic humidity on the d values observed in Antartic snow are greatly modified during the precipitation process. Hence the interpretation of d values in ice cores should be done in the context of a precipitation model.