Recent High-Arctic glacial sediment redistribution: A process perspective using airborne lidar
Recent High-Arctic glacial sediment redistribution: A process perspective using airborne lidar
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DOI：
10.1016/j.geomorph.2010.08.012
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发表时间：
2011
期刊：
影响因子：
3.9
通讯作者：
T. Irvine‐Fynn;N. Barrand;P. R. Porter;A. Hodson;T. Murray
中科院分区：
文献类型：
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作者：
T. Irvine‐Fynn;N. Barrand;P. R. Porter;A. Hodson;T. Murray
高纬度北极地区的冰川逐渐变薄、退缩和质量损失，使前场沉积物越来越多地暴露在流动和重新分布的过程中。在本文中，我们利用 2003 年和 2005 年进行的重复光探测和测距（激光雷达）调查并结合实地观测，对斯瓦尔巴群岛 Midtre Lovénbreen 的前场沉积物重新分布进行了量化。激光雷达勘测确定的观测期内前场的平均地表下降为−0.05ma−1；确定了沉积物改造的两个主要区域：前冰川溪流的活跃河流切割约 2m 和侧冰碛类似程度的下沉。河流和气候现场数据的多变量分析表明，观测到的前场沉积物动员主要由排放强迫驱动，但也有热侵蚀过程和随机、自生沉积物供应的贡献。在观测期间，根据激光雷达数据（3000–4000×103kg）计算的前场河流系统沉积物流失量与河流沉积物负荷监测（1600–3500×103kg）之间的差异表明，正如现场观测所证明的那样，在厚厚的碎片地幔下可能存在大量埋冰。从我们的重复激光雷达调查中发现，冰碛顶部相对均匀的下降表明冰芯的热侵蚀。然而，简单的碎片层厚度模型表明，在较低海拔处，碎片层厚度的变化有所增加，这为冰碛崩解是由热过程和机械过程的复杂组合驱动的断言提供了支持。这项研究证明了使用激光雷达与现场监测相结合以更好地了解沉积冰消动力学和过程的可行性，并强调了前场区域在控制冰消流域沉积物产量方面的重要性。
Progressive glacier thinning, retreat and mass loss in the High-Arctic is increasingly exposing forefield sediments to processes of mobilisation and redistribution. In this paper, we quantify forefield sediment redistribution at Midtre Lovénbreen, Svalbard, using repeat light detection and ranging (lidar) surveys conducted in 2003 and 2005 in combination with field-based observations. Average surface lowering of the forefield over the observation period identified from lidar surveys is −0.05ma−1; and two primary areas of sediment reworking are identified: active fluvial incision of proglacial streams by ~2m and lateral moraine downwasting of similar magnitude. Multivariate analysis of fluvial and climatological field data indicates that observed forefield sediment mobilisation is driven primarily by discharge forcing, but with contributions from thermoerosive processes and stochastic, autogenic sediment supply. During the period of observation, disparity between sediment loss in forefield fluvial systems as calculated from lidar data (3000–4000×103kg) and monitoring of fluvial sediment load (1600–3500×103kg) suggests the likely presence of significant quantities of buried ice beneath a thick debris mantle, as evidenced by field observations. Relatively uniform lowering of the moraine crest identified from our repeat lidar surveys indicates thermoerosion of an ice core. However, simple debris layer thickness modelling indicates an increase in variation of debris layer thickness at lower elevations, providing support for the assertion that moraine disintegration is driven by complex combinations of both thermal and mechanical processes. This study demonstrates the viability of using lidar in conjunction with field monitoring to better understand sedimentary deglaciation dynamics and processes, and also highlights the significance of forefield areas in controlling the sediment yield from deglaciating catchments.