Airborne radar evidence for tributary flow switching in Institute Ice Stream, West Antarctica: Implications for ice sheet configuration and dynamics
Airborne radar evidence for tributary flow switching in Institute Ice Stream, West Antarctica: Implications for ice sheet configuration and dynamics
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DOI：
10.1002/2015jf003518
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发表时间：
2015-09
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影响因子：
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通讯作者：
Kate Winter;J. Woodward;N. Ross;S. Dunning;R. Bingham;H. Corr;M. Siegert
中科院分区：
文献类型：
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作者：
Kate Winter;J. Woodward;N. Ross;S. Dunning;R. Bingham;H. Corr;M. Siegert
尽管冰流对评估西南极冰盖(WAIS)的稳定性很重要，但我们对研究所冰流(IIS)集水区内的中长期动态变化知之甚少。在这里，我们使用机载无线电回波探测来调查埃尔斯沃斯山脉附近IIS上游集水区的冰下地形、内部地层学和全新世水流状况。在三条离散的、地形受限的支流中，通过埃尔斯沃斯槽、独立槽和马蹄谷槽的内部层屈曲，为以前增强的冰盖流动提供了证据。我们认为，在中全新世至晚全新世期间，通过独立海槽和埃尔斯沃斯海槽的冰流增强，是现在被缓慢流动的邦根斯托克冰隆占据的地区冰流的来源。尽管马蹄谷海槽缓慢流动的冰层中也存在屈曲层，但上层冰柱中较厚的表面整合层序列表明，大约4000多年前冰流放缓，因此我们不认为这里的流量增强关闭是由于晚全新世冰流重组。马蹄谷和独立海槽内强烈弯曲的冰层在今天的水流速度下是无法解释的。IIS及其支流冰流的动态性质表明，最近Siple海岸和阿蒙森海区的冰流转换和质量变化并不是这些地区独有的，它们可能在全新世期间是有规律的，可能是WAIS衰落的特征。
Despite the importance of ice streaming to the evaluation of West Antarctic Ice Sheet (WAIS) stability we know little about mid‐ to long‐term dynamic changes within the Institute Ice Stream (IIS) catchment. Here we use airborne radio echo sounding to investigate the subglacial topography, internal stratigraphy, and Holocene flow regime of the upper IIS catchment near the Ellsworth Mountains. Internal layer buckling within three discrete, topographically confined tributaries, through Ellsworth, Independence, and Horseshoe Valley Troughs, provides evidence for former enhanced ice sheet flow. We suggest that enhanced ice flow through Independence and Ellsworth Troughs, during the mid‐Holocene to late Holocene, was the source of ice streaming over the region now occupied by the slow‐flowing Bungenstock Ice Rise. Although buckled layers also exist within the slow‐flowing ice of Horseshoe Valley Trough, a thicker sequence of surface‐conformable layers in the upper ice column suggests slowdown more than ~4000 years ago, so we do not attribute enhanced flow switch‐off here, to the late Holocene ice‐flow reorganization. Intensely buckled englacial layers within Horseshoe Valley and Independence Troughs cannot be accounted for under present‐day flow speeds. The dynamic nature of ice flow in IIS and its tributaries suggests that recent ice stream switching and mass changes in the Siple Coast and Amundsen Sea sectors are not unique to these sectors, that they may have been regular during the Holocene and may characterize the decline of the WAIS.