Estimating englacial radar attenuation using depth profiles of the returned power, central West Antarctica
Estimating englacial radar attenuation using depth profiles of the returned power, central West Antarctica
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使用返回功率的深度剖面估计南极洲西部中部的冰川雷达衰减
DOI：
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发表时间：
2010
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影响因子：
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通讯作者：
C. Raymond
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文献类型：
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作者：
K. Matsuoka;D. Morse;C. Raymond
[1]我们分析了深度模式的几何校正返回功率Pc从冰的西南极洲中部开发一个代理englacial雷达衰减。[Pc]dB（Pc在分贝尺度）在个别网站的深度模式，首先近似与当地平均值[Pc]dB的最小二乘垂直梯度为五个深度范围。这些梯度沿着雷达轨迹的变化显示出可识别的趋势，但在距离小于105 -10公里的范围内具有局部异常特征，这些特征是由陡峭床上方倾斜内层的较小反射和其他因素引起的。因此，从返回功率中提取衰减代理需要减轻反射率变化。接下来，返回的功率仅由在比局部异常特征宽得多的距离上组装的明亮层合成。单个数据集合显示了[Pc]dB的明确上限（而非下限）截止值。截止功率随深度线性下降，在2500和251600 m之间，这定义了上包络梯度。借助衰减和反射率建模，我们得出结论，上包络梯度可以是一个衰减代理的等温冰，预计在上半部分或更多的西南极洲中部。在1600米高空，估计的衰减率变化为5 dB km−1（单向），相当于约2°C的横向温度变化或高达2倍的化学变化。该范围表明，衰减变化可以显著影响基于从床返回的功率对比的床湿度的描绘。
[1] We analyzed depth patterns of geometrically corrected returned power Pc from within the ice of central West Antarctica to develop a proxy for englacial radar attenuation. The depth patterns of [Pc]dB (Pc in the decibel scale) at individual sites were first approximated with least squares vertical gradients of the local mean [Pc]dB for five depth ranges. Variations of these gradients along radar tracks show identifiable trends but have local anomalous features over distances less than ∼5–10 km that are caused by smaller reflection from tilted internal layers above steep beds and other factors. Consequently, extraction of an attenuation proxy from the returned power requires mitigation of reflectivity variations. Next, returned power was synthesized only from bright layers assembled over distances much wider than the local anomalous features. Individual data ensembles show a clear upper (not lower) cutoff in [Pc]dB. The cutoff power decreases with depth linearly between ∼500 and ∼1600 m, which defines the upper envelope gradient. With the aid of attenuation and reflectivity modeling, we concluded that the upper envelope gradient can be an attenuation proxy in the isothermal ice that is expected in the upper half or more of central West Antarctica. The estimated attenuation rate in the upper ∼1600 m varies 5 dB km−1 (one way), equivalent to lateral temperature variations of about 2°C or chemistry variations of up to a factor of 2. This range indicates that the attenuation variations can significantly affect delineation of bed wetness on the basis of contrasts in power returned from the bed.
南极洲西部中部全新世堆积和冰盖动态
影响因子：
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作者：
Neumann, T. A.;Conway, H.;Price, S. F.;Waddington, E. D.;Catania, G. A.;Morse, D. L.
通讯作者：
Morse, D. L.