Layering of surface snow and firn at Kohnen Station, Antarctica: Noise or seasonal signal?
Layering of surface snow and firn at Kohnen Station, Antarctica: Noise or seasonal signal?
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DOI：
10.1002/2016jf003919
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发表时间：
2016-10-01
影响因子：
3.9
通讯作者：
Kipfstuhl, Sepp
中科院分区：
文献类型：
--
作者：
Laepple, Thomas;Hoerhold, Maria;Kipfstuhl, Sepp
冰的密度是监测和模拟冰盖以及模拟孔隙闭合从而解释基于冰芯的温室气体记录的重要属性。一个仍在争论的特征是，在低积累区域可能存在每年一次的雪密度循环。一些研究描述或假设季节性连续的密度层，水平均匀分布，如雷达数据所示。另一方面，对南极洲和格陵兰岛冰芯的高分辨率密度测量显示，在顶部几米没有明显的季节循环。大多数现有的基于雪坑和硬核的研究的一个主要警告是，它们代表了横向非均匀密度场的一个垂直剖面。为了克服这个问题，我们在南极高原东部的Dronning Maud Land的Kohnen站建立了一个广泛的水平和垂直密度数据集。我们钻取并分析了三个90米长的铁芯，以及两个细长雪沟的143个一米长的垂直剖面，以获得密度变化的二维视图。对45米宽和1米深密度场的分析揭示了密度的季节性循环。然而，季节性被强烈的地层噪声覆盖，使得在分析单个岩心时不可见。我们的密度数据集将当地冰芯的视角扩展到百米尺度，从而支持将雷达和地震研究等空间整合方法与冰芯和铁芯联系起来。
The density of firn is an important property for monitoring and modeling the ice sheets as well as to model the pore close-off and thus to interpret ice core-based greenhouse gas records. One feature, which is still in debate, is the potential existence of an annual cycle of firn density in low-accumulation regions. Several studies describe or assume seasonally successive density layers, horizontally evenly distributed, as seen in radar data. On the other hand, high-resolution density measurements on firn cores in Antarctica and Greenland show no clear seasonal cycle in the top few meters. A major caveat of most existing snow-pit and firn-core-based studies is that they represent one vertical profile from a laterally heterogeneous density field. To overcome this, we created an extensive data set of horizontal and vertical density data at Kohnen Station, Dronning Maud Land, on the East Antarctic Plateau. We drilled and analyzed three 90m long firn cores as well as 143 one-meter-long vertical profiles from two elongated snow trenches to obtain a two-dimensional view of the density variations. The analysis of the 45m wide and 1m deep density fields reveals a seasonal cycle in density. However, the seasonality is overprinted by strong stratigraphic noise, making it invisible when analyzing single firn cores. Our density data set extends the view from the local ice core perspective to a hundred meter scale and thus supports linking spatially integrating methods such as radar and seismic studies to ice and firn cores.