Marine ice formation in a suture zone on the Larsen C Ice Shelf and its influence on ice shelf dynamics
Marine ice formation in a suture zone on the Larsen C Ice Shelf and its influence on ice shelf dynamics
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DOI：
10.1002/jgrf.20120
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发表时间：
2013-09-01
影响因子：
3.9
通讯作者：
King, Edward C.
中科院分区：
文献类型：
--
作者：
Jansen, Daniela;Luckman, Adrian;King, Edward C.
南极冰架主要是由流入其中的冰川滋养的。在分隔这些冰川的海岬下游，过冷水会上升并冻结成缝合带，导致海冰的增加。在几个南极冰架上发现了海洋冰体，但对它们的详细几何形状、增生速度或对冰动力学的影响知之甚少。本文研究了南极半岛Larsen C冰架南部Joerg半岛下游缝合带的海冰。我们提供了探地雷达数据，从中我们推断出大气冰的基础，并结合GPS数据和假设流体静力平衡，估计了缝合带内的海冰厚度。研究结果表明，Joerg半岛缝合带中存在海洋冰层，冰盖厚度在20 km范围内从140 m左右增加到180 m左右，表明研究区平均基底吸积速率约为0.5 ma（-1）。我们通过在冰流模型中模拟缝合带来检验这种推断的海冰对冰架动力学的影响。结果与观测到的表面速度和应变速率一致，表明缝合带较温暖、较软的冰有助于引导剪切变形。这使得不同流速的相邻流动单元能够解耦，同时保持冰架的结构完整性。
Antarctic ice shelves are fed primarily by the glaciers flowing into them. Downstream of promontories separating these glaciers, supercooled water can rise and freeze into suture zones, leading to the accretion of marine ice. Marine ice bodies have been found in several Antarctic ice shelves, but little is known about their detailed geometry, rate of accretion, or influence on ice dynamics. In this study, we investigate marine ice in a suture zone downstream of the Joerg Peninsula in the southern part of the Larsen C Ice Shelf, Antarctic Peninsula. We present ground penetrating radar data from which we infer the base of the meteoric ice and, in combination with GPS data and assuming hydrostatic equilibrium, estimate marine ice thickness within a suture zone. We show that the Joerg Peninsula suture zone contains marine ice layer, which is increasing in thickness along flow from similar to 140 m to 180 m over 20 km, implying an average basal accretion rate of similar to 0.5 m a(-1) in our study area. We examined the impact of this inferred marine ice on ice shelf dynamics by modeling the suture zone within an ice flow model. The results, which replicate observed surface velocities and strain rates, show that the warmer and thus softer ice of the suture zone serves to channel shear deformation. This enables decoupling of neighboring flow units with different flow velocities, while maintaining the structural integrity of the ice shelf.