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首页> 外文期刊>The Cryosphere >Using a composite flow law to model deformation in the NEEM deep ice core, Greenland – Part 1: The role of grain size and grain size distribution on deformation of the upper 2207 m
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Using a composite flow law to model deformation in the NEEM deep ice core, Greenland – Part 1: The role of grain size and grain size distribution on deformation of the upper 2207 m

机译：使用复合流法对Meem Deee Ice Ice Ice Ice Ind Mate Greenlation的模拟变形 - 第1部分：晶粒尺寸和粒度分布对鞋面2207米变形的作用

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The effect of grain size on strain rate of ice in the upper 2207 m in the North Greenland Eemian Ice Drilling (NEEM) deep ice core was investigated using a rheological model based on the composite flow law of Goldsby and Kohlstedt (1997, 2001). The grain size was described by both a mean grain size and a grain size distribution, which allowed the strain rate to be calculated using two different model end-members: (i)?the microscale constant stress model where each grain deforms by the same stress and (ii) the microscale constant strain rate model where each grain deforms by the same strain rate. The model results predict that grain-size-sensitive flow produces almost all of the deformation in the upper 2207 m of the NEEM ice core, while dislocation creep hardly contributes to deformation. The difference in calculated strain rate between the two model end-members is relatively small. The predicted strain rate in the fine-grained Glacial ice (that is, ice deposited during the last Glacial maximum at depths of 1419 to 2207 m) varies strongly within this depth range and, furthermore, is about 4–5 times higher than in the coarser-grained Holocene ice (0–1419 m). Two peaks in strain rate are predicted at about 1980 and 2100 m depth. The prediction that grain-size-sensitive creep is the fastest process is inconsistent with the microstructures in the Holocene age ice, indicating that the rate of dislocation creep is underestimated in the model. The occurrence of recrystallization processes in the polar ice that did not occur in the experiments may account for this discrepancy. The prediction of the composite flow law model is consistent with microstructures in the Glacial ice, suggesting that fine-grained layers in the Glacial ice may act as internal preferential sliding zones in the Greenland ice sheet.
机译：谷粒尺寸对北方格陵兰冰钻（Neem）深冰芯上的冰冰中的冰速率的影响，基于Goldsby and Kohlstedt（1997,2001）的流变模型，研究了流变模型。晶粒尺寸和晶粒尺寸分布描述了晶粒尺寸，其允许使用两个不同的模型终端构件计算应变率：（i）？微电尺度恒定应力模型，每个谷物通过相同的压力变形（ii）微尺度恒定应变速率模型，其中每个颗粒通过相同的应变速率变形。模型结果预测，晶粒尺寸敏感流量在Neem冰芯的上部2207米上产生几乎所有变形，而脱位蠕变几乎没有有助于变形。两个模型端构件之间计算的应变率的差异相对较小。细粒冰川冰中的预测应变速率（即，在最后的最后冰川最大值期间沉积在1419至2207米的深度期间沉积的冰）在该深度范围内强烈变化，而且，此外，比其更高的4-5倍约为4-5倍较粗糙的全茂冰（0-1419米）。在约1980年和2100米深度下预测应变速率的两个峰。晶粒尺寸敏感蠕变是最快的过程的预测与全茂年龄冰中的微观结构不一致，表明在模型中低估了位错蠕变的速率。在实验中没有发生的极性冰中的重结晶过程的发生可能占这种差异。复合流动法模型的预测与冰川冰中的微观结构一致，表明冰川冰中的细粒层可以作为格陵兰冰盖中的内部优先滑动区。

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