Processes involved in the propagation of rifts near Hemmen Ice Rise, Ronne Ice Shelf, Antarctica
Processes involved in the propagation of rifts near Hemmen Ice Rise, Ronne Ice Shelf, Antarctica
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DOI：
10.3189/172756504781829837
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发表时间：
2004-12
影响因子：
3.4
通讯作者：
E. Larour;E. Rignot;D. Aubry
中科院分区：
文献类型：
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作者：
E. Larour;E. Rignot;D. Aubry
摘要利用ERS-1、ERS-2和RADAR-SAT-1卫星采集的干涉雷达图像，观测了南极罗恩冰架沿海曼冰隆延伸的裂隙破裂尖端。1992年和1997年产生的干涉图使观测到的冰变形分别累积了9天和24天。这些干涉图被组合在一起，以便将蠕变变形的连续过程与海潮变化引起的更周期性的运动分开。对蠕变变形的局部梯度的研究揭示了破裂尖端和裂缝周围和附近的冰变形模式，具有很高的精度(最高可达10 cm a-1)。我们将观测结果与冰形变模型进行了比较，得到以下结果：(1)罗恩冰架的潮汐振荡只产生沿裂谷和破裂尖端附近的小变形。(2)沿冰锋、裂隙和破裂尖端观察到垂直弯曲，这与冰的粘性变形模型有很好的关系。此外，该模型还指出，在断裂尖端观察到的变形模式是裂谷扩展状态(即活动与非活动)的敏感指示器。(3)冰的粘性调整是变形的主要方式，掩盖了线弹性断裂力学(LEFM)预测的变形模式。(4)在相当于裂谷长度的空间尺度上，LEFM很好地预测了传播速率。
Abstract Interferometric radar images collected by ERS-1, ERS-2 and RADAR- SAT-1 are used to observe the rupture tip of rifts that propagate along Hemmen Ice Rise on the Ronne Ice Shelf, Antarctica. Interferograms generated in 1992 and 1997 allow for the observation of ice deformation accumulated over 9 and 24 days respectively. These interferograms are combined, in order to separate the continuous process of creep deformation from the more cyclic motion caused by variations in ocean tide. An examination of local gradients in creep deformation reveals the pattern of ice deformation around and near the rupture tips and rifts with great precision (up to 10 cm a-1). We compare the observations with a deformation model for ice and obtain the following results: (1) The tidal oscillation of the Ronne Ice Shelf only yields small deformations along the rifts and near the rupture tips. (2) Along the ice front, the rifts and at the rupture tips, vertical bending is observed which is well explained by a model of viscous deformation of ice. Furthermore, the model indicates that the deformation pattern observed at the rupture tips is a sensitive indicator of the propagation state of the rifts (i.e. active vs inactive). (3) The viscous adjustment of ice is the dominant mode of deformation, masking the deformation pattern predicted by linear elastic fracture mechanics (LEFM). (4) Yet, at a spatial scale equivalent to the length of a rift, the propagation rate is well predicted by LEFM.