Physically based summer temperature reconstruction from melt layers in ice cores
Physically based summer temperature reconstruction from melt layers in ice cores
复制标题
根据冰芯融化层进行基于物理的夏季温度重建
DOI：
10.1029/2020ea001590
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
and T. Aoki
中科院分区：
文献类型：
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作者：
Fujita;K.;S. Matoba;Y. Iizuka;N. Takeuchi;A. Tsushima;Y. Kurosaki;and T. Aoki
以前从冰芯重建夏季温度依赖于融化层和附近站点观测到的温度之间的统计关系。这项研究提出了一种从冰芯融化层中重建夏季温度的新方法，该方法使用了一个能量平衡模型，该模型结合了热传导和积雪中融化水的重新冻结。我们使用ERA-中期再分析数据集的季节模式来计算不同夏季平均温度(SMT)和年降水量条件下降雪内的再冻水量，并编制了包含这三个变量的校准表。然后，我们根据再冻结量和年累积量来估计SMT，这两者都可以从冰芯中获得。我们将这种方法应用于从不同气候的地点回收的四个冰芯：两个在格陵兰冰盖上，一个在阿拉斯加，一个在俄罗斯阿拉泰。重建的SMT显示出与附近站点观测到的温度类似的变化。不同部位SMT与熔体厚度之间的非线性关系不同，表明不能用单一的线性近似来估计SMT。敏感性分析表明，年较差、年降水量和降雪反照率(在模式中是一个时间不变的值)显著影响SMT与熔层厚度的关系。这一新方法提供了现有方法的替代方法，并从受融化影响的冰芯中产生了SMT的独立估计。
Previous reconstructions of summer temperatures from ice cores have relied on a statistical relationship between a melt layer and temperature observed at nearby stations. This study presents a novel method for reconstructing summer temperatures from melt layers in ice cores using an energy balance model that incorporates heat conduction and meltwater refreezing in the firn. We use the seasonal patterns in the ERA‐Interim reanalysis data set for an ice core site to calculate the amounts of refreezing water within the firn under various summer mean temperature (SMT) and annual precipitation conditions, and prepared calibration tables containing these three variables. We then estimate the SMTs from the refreezing amount and annual accumulation, both of which can be obtained from an ice core. We apply this method to four ice cores that were recovered from sites with different climates: two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai. The reconstructed SMTs show comparable variations with those of observed temperatures at nearby stations. The nonlinear relationship between SMT and melt layer thickness differs between sites, indicating that a single linear approximation cannot be employed to estimate SMT. Sensitivity analyses suggest that the annual temperature range, amount of annual precipitation, and firn albedo (which is a time‐invariant value in the model) significantly affect the relationship between SMT and melt layer thickness. This new method provides an alternative to existing approaches and yields an independent estimate of SMT from ice cores that have been affected by melting.