The Southern Patagonian Icefield shows rapid retreat and thinning with variability in magnitude and timing among individual glaciers. To better understand these heterogeneous changes, we estimated the ice thickness distribution within the middle and lower basins of Perito Moreno, Upsala, and Viedma freshwater calving glaciers during the 2017–2018 period. We employed a surface velocity inversion method that incorporates glacier motion through internal deformation and basal slip. Additionally, we applied a directional smoothing filter to estimate surface slope and a calibration process to improve model accuracy. Based on the estimated bed elevation, we introduced an index of relative terminus stability, calculated as the ratio between the height of the ice cliff at the calving front and the water depth at the glacier terminus. Our results show a good performance of model, with a mean RMSE of 77.5 m and correlations >0.89 between observed and modeled ice thickness. Perito Moreno glacier shows ice thickness ranging from 200 to 700 m along its centerline, from the calving front to 15 km upstream. It also displays a stability index four times higher than the other two glaciers, which may explain its relatively stable behavior. In contrast, the Upsala and Viedma glaciers exhibit much thicker ice both at the terminus and higher elevations, with stability indexes close to floating near the calving front. We found that retreat rates of 200 m a, coupled with thinning rates of 10 m a, can propagate the close to floating conditions of the ice up-glacier. The Upsala and Viedma glaciers have reached these values, which can account for their rapid mass loss. Our results and methodology contribute to the understanding and monitoring of calving glaciers' stability in the region.

中文翻译：

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南巴塔哥尼亚冰原东侧三个大型淡水崩解冰川的冰厚分布和稳定性

南巴塔哥尼亚冰原表现出快速的退缩和变薄，各个冰川的大小和时间存在差异。为了更好地了解这些异质变化，我们估计了2017-2018年期间佩里托莫雷诺、乌普萨拉和别德马淡水崩解冰川中下游盆地的冰厚度分布。我们采用了表面速度反演方法，该方法通过内部变形和基底滑动结合了冰川运动。此外，我们应用方向平滑滤波器来估计表面坡度，并应用校准过程来提高模型精度。根据估计的床高程，我们引入了相对终点稳定性指数，计算为崩解前缘冰崖高度与冰川终点水深之比。我们的结果显示模型具有良好的性能，平均 RMSE 为 77.5 m，观测到的冰厚度与模拟的冰厚度之间的相关性 > 0.89。佩里托莫雷诺冰川沿其中心线，从崩解前沿到上游 15 公里，冰层厚度为 200 至 700 m。它还显示出比其他两个冰川高四倍的稳定性指数，这可以解释其相对稳定的行为。相比之下，乌普萨拉和别德马冰川在终点和较高海拔处都呈现出更厚的冰，稳定性指数接近于漂浮在崩解前沿附近。我们发现，200 Ma 的退缩率加上 10 Ma 的稀疏率，可以传播冰川上冰接近漂浮的状态。乌普萨拉和别德马冰川已经达到了这些值，这可以解释它们的质量迅速流失的原因。我们的结果和方法有助于了解和监测该地区崩解冰川的稳定性。