Spatial variation of englacial radar attenuation: Modeling approach and application to the Vostok flowline
Spatial variation of englacial radar attenuation: Modeling approach and application to the Vostok flowline
复制标题
冰川雷达衰减的空间变化：建模方法及其在东方流线中的应用
DOI：
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
F. Pattyn
中科院分区：
文献类型：
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作者：
J. MacGregor;K. Matsuoka;E. Waddington;D. Winebrenner;F. Pattyn
[1]约束冰内雷达衰减的空间变化是从雷达回波功率准确推断冰盖冰内和基底性质空间变化的关键。在这里，我们评估衰减模型，占冰的温度和化学的空间变化，并测试他们沿着流线，通过东方冰芯网站，南极洲。最简单的模型经常使用，但很少有效，它假定沿着出油管各处的衰减率均匀，因此总衰减与冰厚成比例。下一个最简单的模型使用冰流模型预测的空间变化的温度，并假设均匀的化学。额外的模型占空间变化的化学使用冰内地层学。我们发现，往返衰减到床可以很容易地由10 dB或更多的均匀衰减率模型和模型，占可变冰温度之间的差异。这种差异足以混淆干床和湿床的划分。还包括化学中的空间变化产生较小的差异（<10 dB），但是这些差异的大小取决于过去杂质的干沉积和湿沉积的相对重要性。考虑干沉积杂质需要冰流建模，并导致与所有其他模型存在更大差异，其他模型仅假设化学成分均匀或湿沉积。这些结果表明，模拟衰减的空间变化需要一个空间变化的温度模型，以准确地推断床床条件床返回功率，冰芯数据和雷达地层学也是非常可取的。
[1] Constraining the spatial variation of englacial radar attenuation is critical for accurate inference of the spatial variation of the englacial and basal properties of ice sheets from radar returned power. Here we evaluate attenuation models that account for spatial variations in ice temperature and chemistry and test them along the flowline that passes through the Vostok ice core site, Antarctica. The simplest model, often used but rarely valid, assumes a uniform attenuation rate everywhere along the flowline, so that total attenuation is proportional to ice thickness. The next simplest model uses spatially varying temperatures predicted by an ice-flow model and assumes uniform chemistry. Additional models account for spatially varying chemistry using englacial stratigraphy. We find that the roundtrip attenuation to the bed can easily differ by 10 dB or more between the uniform attenuation-rate model and models that account for variable ice temperature. Such differences are sufficient to confound the delineation of dry and wet beds. Also including spatial variations in chemistry produces smaller differences (<10 dB), but the magnitude of these differences depends on the relative importance of dry and wet deposition of impurities in the past. Accounting for dry-deposited impurities requires ice-flow modeling and results in larger differences from all other models, which assume uniform chemistry or wet deposition only. These results indicate that modeling the spatial variation of attenuation requires a spatially varying temperature model in order to infer bed conditions from bed returned power accurately, and that both ice core data and radar stratigraphy are also strongly desirable.
DOI：
10.5194/tc-4-447-2010
发表时间：
2010
期刊：
The Cryosphere
影响因子：
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作者：
Jacobel R
通讯作者：
Jacobel R