Advances in analytical methods have made it possible to obtain high-resolution water isotopic data from ice cores. Their spectral signature contains information on the diffusion process that attenuated the isotopic signal during the firn densification process. Here, we provide a tool for estimating firn-diffusion rates that builds on the Community Firn Model. Our model requires two main inputs, temperature and accumulation, and it calculates the diffusion lengths for δ17O, δ18O and δD. Prior information on the isotopic signal of the precipitation is not a requirement. In combination with deconvolution techniques, diffusion lengths can be used in order reconstruct the pre-diffusion isotopic signal. Furthermore, the temperature dependence of the isotope diffusion and firn densification makes the diffusion length an interesting candidate as a temperature proxy. We test the model under steady state and transient scenarios and compare four densification models. Comparisons with ice core data provide an evaluation of the four models and indicate that there are differences in their performance. Combining data-based diffusion length estimates with information on past accumulation rates and ice flow thinning, we reconstruct absolute temperatures from three Antarctic ice core sites.

中文翻译：

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使用 Community Firn 模型进行 firn 同位素扩散的数值实验

分析方法的进步使得从冰芯中获得高分辨率水同位素数据成为可能。它们的光谱特征包含有关在纤维致密化过程中减弱同位素信号的扩散过程的信息。在这里，我们提供了一个基于 Community Firn 模型来估计 firn 扩散率的工具。我们的模型需要两个主要输入，温度和累积，它计算 δ 的扩散长度17O, δ18O 和 δD。降水同位素信号的先验信息不是必需的。结合反卷积技术，可以使用扩散长度来重建预扩散同位素信号。此外，同位素扩散和纤维致密化的温度依赖性使扩散长度成为一个有趣的温度代理候选者。我们在稳态和瞬态场景下测试模型并比较四种致密化模型。与冰芯数据的比较提供了对四种模型的评估，并表明它们的性能存在差异。将基于数据的扩散长度估计与过去积累率和冰流变薄的信息相结合，我们重建了三个南极冰芯站点的绝对温度。