Deglacierization of a Marginal Basin and Implications for Outburst Floods, Mendenhall Glacier, Alaska
Deglacierization of a Marginal Basin and Implications for Outburst Floods, Mendenhall Glacier, Alaska
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DOI：
10.3389/feart.2020.00137
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发表时间：
2020-05-27
影响因子：
2.9
通讯作者：
Conaway, Jeffrey S.
中科院分区：
文献类型：
--
作者：
Kienholz, Christian;Pierce, Jamie;Conaway, Jeffrey S.
自杀盆地是阿拉斯加州门登霍尔冰川的一个部分冰川化的边缘盆地，自 2011 年以来，每年都会发生冰川湖溃决洪水 (GLOF)。洪水导致门登霍尔山谷被淹没和侵蚀，影响房屋和其他基础设施。在这里，我们利用现场和遥感数据来评估自杀盆地的近期演变和现状。我们重点关注 2018 年和 2019 年的融化季节，在此期间我们收集了大部分数据，其中部分数据是使用无人机 (UAV) 收集的。为了提供长期背景，我们分析了 2006 年以来收集的 DEM，并对 2006-2019 年期间的冰川表面质量平衡进行了建模。在 2018 年和 2019 年爆发洪水事件期间，自杀盆地在大约 4-5 天内释放了大约 30 x 10(6) m(3) 的水。由于这两年湖泊排水都是部分的，因此这些类似于 30 x 10(6) m(3) 的湖泊仅占流域总存储容量的一小部分（大约 60%）。与往年不同的是，冰下排水先于冰坝上的冰上流出，持续时间约为2018年1天和2019年6天。2018年和2019年发生了两次大型崩解事件，在湖泊充水过程中，水下冰从主冰川上脱落，从而增加了盆地的蓄水能力。 2018年，流域浮冰平均厚度为36 m。 2019年，冰厚为29 m，这表明尽管门登霍尔冰川的冰流入量有所增加，但冰舌仍在快速腐烂。 2018年至2019年，流域入口处的冰坝变薄了5 m a(-1)以上，大约是2006-2018年参考期的两倍。虽然冰坝变薄降低了流域的蓄水能力，但流域内冰量的减少和湖泊纵向扩张却增加了蓄水能力，而后者的过程很难预测。过早排水开始（即在达到湖泊蓄水能力之前排水）、间歇性排水减速和提前排水终止的可能性使未来 GLOF 事件的预测进一步复杂化。
Suicide Basin is a partly glacierized marginal basin of Mendenhall Glacier, Alaska, that has released glacier lake outburst floods (GLOFs) annually since 2011. The floods cause inundation and erosion in the Mendenhall Valley, impacting homes and other infrastructure. Here, we utilize in-situ and remote sensing data to assess the recent evolution and current state of Suicide Basin. We focus on the 2018 and 2019 melt seasons, during which we collected most of our data, partly using unmanned aerial vehicles (UAVs). To provide longer-term context, we analyze DEMs collected since 2006 and model glacier surface mass balance over the 2006-2019 period. During the 2018 and 2019 outburst flood events, Suicide Basin released similar to 30 x 10(6) m(3) of water within approximately 4-5 days. Since lake drainage was partial in both years, these similar to 30 x 10(6) m(3) represent only a fraction (similar to 60%) of the basin's total storage capacity. In contrast to previous years, subglacial drainage was preceded by supraglacial outflow over the ice dam, which lasted similar to 1 day in 2018 and 6 days in 2019. Two large calving events occurred in 2018 and 2019, with submerged ice breaking off the main glacier during lake filling, thereby increasing the basin's storage capacity. In 2018, the floating ice in the basin was 36 m thick on average. In 2019, ice thickness was 29 m, suggesting rapid decay of the ice tongue despite increasing ice inflow from Mendenhall Glacier. The ice dam at the basin entrance thinned by more than 5 m a(-1) from 2018 to 2019, which is approximately double the rate of the reference period 2006-2018. While ice-dam thinning reduces water storage capacity in the basin, that capacity is increased by declining ice volume in the basin and longitudinal lake expansion, with the latter process challenging to predict. The potential for premature drainage onset (i.e., drainage before the lake's storage capacity is reached), intermittent drainage decelerations, and early drainage termination further complicates prediction of future GLOF events.