We present continuous estimates of snow and firn density, layer depth and accumulation from a multi-channel, multi-offset, ground-penetrating radar traverse. Our method uses the electromagnetic velocity, estimated from waveform travel-times measured at common-midpoints between sources and receivers. Previously, common-midpoint radar experiments on ice sheets have been limited to point observations. We completed radar velocity analysis in the upper ~2 m to estimate the surface and average snow density of the Greenland Ice Sheet. We parameterized the Herron and Langway (1980) firn density and age model using the radar-derived snow density, radar-derived surface mass balance (2015–2017) and reanalysis-derived temperature data. We applied structure-oriented filtering to the radar image along constant age horizons and increased the depth at which horizons could be reliably interpreted. We reconstructed the historical instantaneous surface mass balance, which we averaged into annual and multidecadal products along a 78 km traverse for the period 1984–2017. We found good agreement between our physically constrained parameterization and a firn core collected from the dry snow accumulation zone, and gained insights into the spatial correlation of surface snow density.

中文翻译：

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从 GreenTrACS 多偏移探地雷达重建 1984-2017 年的历史地表质量平衡

我们通过多通道、多偏移量、探地雷达遍历对雪和冷杉密度、层深度和累积进行了连续估计。我们的方法使用电磁速度，根据在源和接收器之间的公共中点测量的波形传播时间估计。以前，冰盖上的共中点雷达实验仅限于点观测。我们完成了上部~2 m 的雷达速度分析，以估计格陵兰冰盖的表面和平均积雪密度。我们使用雷达衍生的雪密度、雷达衍生的表面质量平衡 (2015-2017) 和再分析衍生的温度数据对 Herron 和 Langway (1980) 的杉木密度和年龄模型进行了参数化。我们沿恒定年龄层对雷达图像应用了面向结构的滤波，并增加了可以可靠解释层位的深度。我们重建了历史瞬时地表质量平衡，我们将其平均为沿 78公里遍历 1984-2017 年期间。我们发现我们的物理约束参数化与从干雪堆积区收集的冰芯之间有很好的一致性，并深入了解了地表雪密度的空间相关性。