Geometry and dynamics of an East Antarctic Ice Sheet outlet glacier, under past and present climates
Geometry and dynamics of an East Antarctic Ice Sheet outlet glacier, under past and present climates
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DOI：
10.1029/2011jf002028
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发表时间：
2011-09
影响因子：
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通讯作者：
N. Golledge;R. Levy
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文献类型：
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作者：
N. Golledge;R. Levy
[1] 南极东部冰盖（EAIS）出口冰川的行为无论是在当前还是在最近的地质历史中，无论是从理解当代冰川动力学的力学角度，还是从上皮里奥-更新世气候转变期间的时代尺度冰盖稳定性的角度来看，都引起了相当大的兴趣。在这里，我们使用冰川流线模型，该模型结合了纵向应力的影响，对费拉尔冰川进行数值模拟，首先在当今的环境条件下，然后在较冷和较温暖的气候条件下分别代表末次盛冰期（LGM）和上新世中期的峰值温暖。使用机载雷达剖面、InSAR 导出的表面速度、冰芯和地质数据作为经验约束，我们提出了一种诊断模拟，该模拟使用迭代方法来精确再现观测到的动力学。我们的模型表明，在目前的条件下，冰川主要是基于冷的，主要通过内部变形流动，并且由于横截面山谷几何形状的变化、冰川表面的局部陡峭以及纵向耦合的非局部效应的综合作用，在基岩山脊上形成“瀑布”。在较冷、较干燥的末次盛冰期气候下，对低剖面冰川进行时间相关（进化）模拟，预测流速低于目前，基岩侵蚀或底耕流量最小。相反，比现在温暖的上新世中期气候产生了更具活力的冰川，该冰川以温暖为基础，并沿着其大部分河床滑动。我们认为，费拉尔等 EAIS 出口冰川会沿着其长度动态响应不断变化的环境强迫，其中最显着的变化发生在其下游。对上游流域扰动的调整更加温和。
[1] The behavior of East Antarctic Ice Sheet (EAIS) outlet glaciers both at present and during the recent geological past is of considerable interest both from the point of view of understanding the mechanics of contemporary glacier dynamics, and also with regard to epoch-scale ice sheet stability during Plio-Pleistocene climate transitions. Here we use a glacier flowline model that incorporates the effects of longitudinal stresses to numerically simulate Ferrar Glacier, first under present-day environmental conditions, and subsequently under both colder and warmer climate regimes representing the Last Glacial Maximum (LGM) and mid-Pliocene peak warmth respectively. Using airborne radar profiles, InSAR-derived surface velocities, ice core and geological data for empirical constraint, we present a diagnostic simulation that uses an iterative method to closely reproduce observed dynamics. Our model suggests that the glacier is largely cold-based under present conditions, flows predominantly by way of internal deformation, and ‘cascades’ over bedrock ridges due to the combined action of changes in cross-sectional valley geometry, local steepening of the glacier surface, and the non-local effects of longitudinal coupling. Time-dependent (evolutionary) simulation of a lower-profile glacier under a colder, drier, LGM climate, predicts flow velocities lower than present with minimal bedrock erosion or basal till flux. Conversely, the warmer-than-present mid-Pliocene climate produces a more dynamic glacier that is warm-based and sliding along much of its bed. We propose that EAIS outlet glaciers, such as the Ferrar, respond dynamically along their length in response to changing environmental forcings, with most significant changes taking place in their lower reaches. Adjustment to perturbations in upper catchments is more muted.