Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland
Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland
复制标题
格陵兰岛大气与雪面之间的蒸气交换过程中同位素分馏的证据
DOI：
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
D. Dahl
中科院分区：
文献类型：
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作者：
M. Madsen;H. Steen‐Larsen;H. Steen‐Larsen;M. Hörhold;S. Berben;Emilie Capron;Emilie Capron;Anne;Alun Hubbard;Mari F. Jensen;T. Jones;S. Kipfstuhl;I. Koldtoft;H. Pillar;Bruce H. Vaughn;D. Vladimirova;D. Dahl;D. Dahl
格陵兰岛和南极洲最近的几项研究报告了降水事件之间近地表雪的水同位素组成的显着变化。这些变化与大气水蒸气的同位素交换和升华诱导的分馏有关，但这些过程受到观测的限制很小。理解和量化这些过程对于解释冰芯气候代用指标和制定同位素支持的大气环流模型至关重要。在这里，我们连续测量了地表雪和大气蒸汽中的水同位素组成，以及近地表大气湍流和雪-空气潜热和显热通量，这些都是2016年夏季在东格陵兰冰芯项目钻探现场获得的。在两个为期4天的时间段内，观察到大气水同位素的显著日变化。一个模型来探索这种变化对地表雪同位素组成的影响。我们的模型表明，在雪的上部亚厘米的雪同位素组成表现出日变化，在δ 18 O和δD的振幅分别为~2.5‰和~13‰。相比之下，这种变化相当于格陵兰内部积雪同位素季节变化幅度的10-20%，以及冰川-间冰期过渡期间的变化。重要的是，我们的观测和模型结果表明，在格陵兰东北部夏季无云条件下，在昼夜时间尺度上模拟水汽和雪表面之间的交换时，需要考虑升华诱导的分馏。
Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near‐surface snow between precipitation events. These changes have been linked to isotopic exchange with atmospheric water vapor and sublimation‐induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes are crucial to both the interpretation of ice core climate proxies and the formulation of isotope‐enabled general circulation models. Here, we present continuous measurements of the water isotopic composition in surface snow and atmospheric vapor together with near‐surface atmospheric turbulence and snow‐air latent and sensible heat fluxes, obtained at the East Greenland Ice‐Core Project drilling site in summer 2016. For two 4‐day‐long time periods, significant diurnal variations in atmospheric water isotopologues are observed. A model is developed to explore the impact of this variability on the surface snow isotopic composition. Our model suggests that the snow isotopic composition in the upper subcentimeter of the snow exhibits a diurnal variation with amplitudes in δ18O and δD of ~2.5‰ and ~13‰, respectively. As comparison, such changes correspond to 10–20% of the magnitude of seasonal changes in interior Greenland snow pack isotopes and of the change across a glacial‐interglacial transition. Importantly, our observation and model results suggest, that sublimation‐induced fractionation needs to be included in simulations of exchanges between the vapor and the snow surface on diurnal timescales during summer cloud‐free conditions in northeast Greenland.