Lemon Creek Glacier, a temperate valley glacier in the Juneau Icefield of Southeast Alaska, is the site of long running (>60 years) glaciological studies. However, the most recent published estimates of its thickness and subglacial topography come from two ~50 years old sources that are not in agreement and do not account for the effects of years of negative mass balance. We collected a 1-km long active-source seismic line on the upper section of the glacier parallel and near to the centerline of the glacier, roughly straddling the equilibrium-line altitude. We used these data to perform joint reflection-refraction velocity modeling and reflection imaging of the glacier bed. We find that this upper section of Lemon Creek Glacier is as much as 150 m (~65%) thicker than previously suggested with a large overdeepening in an area previously believed to have a uniform thickness. Our results lead us to reinterpret the impact of basal motion on ice flow and have a significant impact on expectations of subglacial hydrology. We suggest that further efforts to develop a whole-glacier model of subglacial topography are necessary to support studies that require accurate models of ice thickness and subglacial topography.

中文翻译：

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来自主动源地震成像的阿拉斯加柠檬溪冰川的冰层厚度估计

柠檬溪冰川是阿拉斯加东南部朱诺冰原的温带山谷冰川，是长期（>60 年）冰川学研究的地点。然而，最近发表的对其厚度和冰下地形的估计来自两个约 50 年的来源，这些来源不一致，也没有考虑到多年负质量平衡的影响。我们在冰川上部平行并靠近冰川中心线收集了一条 1 公里长的活动源地震线，大致跨越平衡线高度。我们使用这些数据对冰川床进行联合反射-折射速度建模和反射成像。我们发现 Lemon Creek Glacier 的这个上部比之前建议的要厚 150 m (~65%)，在之前认为具有均匀厚度的区域有很大的过度加深。我们的结果使我们重新解释了基础运动对冰流的影响，并对冰下水文的预期产生了重大影响。我们建议，有必要进一步努力开发整个冰川的冰下地形模型，以支持需要准确的冰厚度和冰下地形模型的研究。