Coevolution of continental ice cover and permafrost extent over the last glacial‐interglacial cycle in North America
Coevolution of continental ice cover and permafrost extent over the last glacial‐interglacial cycle in North America
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北美末次冰期-间冰期旋回大陆冰盖与多年冻土范围的协同演化
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
W. Peltier
中科院分区：
文献类型：
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作者：
L. Tarasov;W. Peltier
床的热特性的冰川系统模型，已被校准对一个大的相对海平面，大地测量，和strandline观测检查以前的冰川部门的北美大陆。该模型比较有利的永久冻土的范围，并对从三个深钻孔时，适当的床热导率观测到的温度分布。估计现今的深度场的下部永久冻土边界。我们发现一个显着的不平衡，在较低的永久冻土层边界的北极地区，与现今的深度高达250浅于现今的气候强迫的平衡值。这在很大程度上是由于对冰川期冰盖丧失的持续反应。冰下温暖的面积分数的时间演变也与校准导出的置信区间。在末次盛冰期获得了50% ± 6%的峰值暖基分数。最大的三个冰体积最大值的时间，在最后一次冰期周期的轨道强迫的dupinity组件的响应相匹配的最大值的温暖的面积分数没有显着的相位延迟。需要基于温度的条件，以在模型中启用冰流（快速流动）。因此，据推测，在最激烈的增长和衰退阶段，暖基冰覆盖面积的扩大在产生高度动态冰盖方面发挥了关键作用。
The bed thermal characteristics of a glacial systems model that has been calibrated against a large set of relative sea level, geodetic, and strandline observations are examined for the previously glaciated sector of the North American continent. The model compares favorably against the present-day extent of permafrost and against the observed temperature profiles from three deep boreholes when appropriate bed thermal conductivities are employed. Estimates for the present-day depth field of the lower permafrost boundary are presented. We find a significant disequilibrium in the lower permafrost boundary for most of the Arctic region, with present-day depth as much as 250 in shallower than the equilibrium value for present-day climate forcing. This is largely due to the ongoing response to the loss of ice cover from the glacial period. The time evolution of the subglacial warm-based area fraction is also presented together with calibration-derived confidence intervals. A peak warm-based fraction of 50% ± 6% is obtained at Last Glacial Maximum. The timing of the three largest ice volume maxima that were produced in response to the obliquity component of orbital forcing during the last glacial cycle matches that of the maxima for the warm-based area fraction with no significant phase delay. Warm-based conditions are required to enable ice streaming (fast flow) in the model. It is therefore hypothesized that the expansion of the area covered by warm-based ice played a critical role in producing a highly dynamic ice sheet during both the most intense growth and recession phases.