Diffuse debris entrainment in glacier, lab and model environments
Diffuse debris entrainment in glacier, lab and model environments
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冰川、实验室和模型环境中的弥漫碎片夹带
DOI：
10.1017/aog.2023.31
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发表时间：
2023
影响因子：
2.9
通讯作者：
Meyer, Colin R.
中科院分区：
文献类型：
--
作者：
Rempel, Alan W.;Hansen, Dougal D.;Zoet, Luke K.;Meyer, Colin R.
在多晶冰川冰中，少量的液态水衬在三重连接点上，形成了连接的矿脉网络，使物质能够与底层的基底环境进行交换。在冰缘地区通常观察到的碎片扩散集中可能归因于这一机制。在最近的低温环剪实验中，我们观察到几十微米大小的黄土颗粒沿沿着晶界的侵位。在这里，我们描述了一个理想化的静脉液体流动模型，以阐明有利于这种颗粒运输的条件。液体势中的溶质驱动流向较冷的温度和较低的溶质浓度，而冰应力状态与流体静力平衡的偏差产生了额外的吸力，流向异常低的冰压。我们的模型预测粒子夹带后，温和的变暖沿着的基底界面所产生的预期的自然变化的有效应力，和内部松弛的温度和溶质浓度由我们的实验方案。与实验观察的比较是令人鼓舞的，但建议，液体流速有点高和/或更有效地拖动较大的颗粒比我们的理想化模型与标称参数的选择。扩散碎片夹带延伸到冰川床上方数米，可能需要更复杂的处理，包括冰变形或其他过程的影响。
Small quantities of liquid water lining triple junctions in polycrystalline glacier ice form connected vein networks that enable material exchange with underlying basal environments. Diffuse debris concentrations commonly observed in ice marginal regions might be attributed to this mechanism. Following recent cryogenic ring-shear experiments, we observed emplacement along grain boundaries of loess particles several tens of microns in size. Here, we describe an idealized model of vein liquid flow to elucidate conditions favoring such particle transport. Gradients in liquid potential drive flow toward colder temperatures and lower solute concentrations, while deviations of the ice stress state from hydrostatic balance produce additional suction toward anomalously low ice pressures. Our model predicts particle entrainment following both modest warming along the basal interface resulting from anticipated natural changes in effective stress, and the interior relaxation of temperature and solute concentration imposed by our experimental protocols. Comparisons with experimental observations are encouraging, but suggest that liquid flow rates are somewhat higher and/or more effective at dragging larger particles than predicted by our idealized model with nominal parameter choices. Diffuse debris entrainment extending several meters above the glacier bed likely requires a more sophisticated treatment that incorporates effects of ice deformation or other processes.