High-resolution study of layering within the percolation and soaked facies of the Greenland ice sheet
High-resolution study of layering within the percolation and soaked facies of the Greenland ice sheet
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DOI：
10.3189/172756411799096286
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发表时间：
2011-01-01
影响因子：
2.9
通讯作者：
Bradford, John
中科院分区：
文献类型：
--
作者：
Brown, Joel;Harper, Joel;Bradford, John
在格陵兰冰盖的渗流和浸泡相中，雷达内反射层位和骨灰盒柱层状结构之间的关系尚不清楚。我们进行了两次小规模的探地雷达(GPR)调查，并在格陵兰冰盖的渗流相和浸泡相收集了10米的降雪岩芯。这两次调查相隔的距离类似于50公里，海拔接近340米，导致年平均融化持续时间相差类似40天。在融化程度较低的较高地段(类似于1997 ma.s.l)，我们发现在G PR数据中识别的内反射层在网格上基本上是横向连续的；然而，在1.5~14.0m的距离内，无法在岩心之间追踪到岩心中识别的地层，因此，我们发现直接观测的积雪岩心地层与雷达获取的内反射层之间没有相关性。在较低的位置(类似于1660米)，融化较多，我们发现了巨大的冰层，厚度为0.5米，地层边界水平跨度为15米。一些冰层和地层边界与雷达网格区域内横向连续的内部反射层位有很好的相关性。确定的内反射层位与1997年海平面相似。可能是年度等时线，但反射层位类似于1660 ma.s.l。很可能是多年的特征。我们发现，通过将岩心地层学与雷达层位捆绑在一起进行远距离填图积累速度可能会导致模糊的结果，因为：(1)1997年m处的降雪岩心之间没有地层对比；(2)1660m处的反射层是多年特征。
Within the percolation and soaked facies of the Greenland ice sheet, the relationship between radar-derived internal reflection horizons and the layered structure of the urn column is unclear. We conducted two small-scale ground-penetrating radar (GPR) surveys in conjunction with 10 m firn cores that we collected within the percolation and soaked facies of the Greenland ice sheet. The two surveys were separated by a distance of similar to 50 km and similar to 340 m of elevation leading to similar to 40 days of difference in the duration of average annual melt. At the higher site (similar to 1997 m a.s.l.), which receives less melt, we found that internal reflection horizons identified in G PR data were largely laterally continuous over the grid; however, stratigraphic layers identified in cores could not be traced between cores over any distance from 1.5 to 14.0 m. Thus, we found no correlation between firn core stratigraphy observed directly and radar-derived internal reflection horizons. At the lower site (similar to 1660 m a.s.l.), which receives more melt, we found massive ice layers >0.5 m thick and stratigraphic boundaries that span >15 m horizontally. Some ice layers and stratigraphic boundaries correlate well with internal reflection horizons that are laterally continuous over the area of the radar grid. Internal reflection horizons identified at similar to 1997 m a.s.l. are likely annual isochrones, but the reflection horizons identified at similar to 1660 m a.s.l. are likely multi-annual features. We find that mapping accumulation rates over long distances by tying core stratigraphy to radar horizons may lead to ambiguous results because: (1) there is no stratigraphic correlation between firn cores at the 1997 m location; and (2) the reflection horizons at the 1660 m location are multi-annual features.