Discovery of relict subglacial lakes and their geometry and mechanism of drainage.
Discovery of relict subglacial lakes and their geometry and mechanism of drainage.
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DOI：
10.1038/ncomms11767
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发表时间：
2016-06-13
影响因子：
16.6
通讯作者：
Fowler AC
中科院分区：
文献类型：
--
作者：
Livingstone SJ;Utting DJ;Ruffell A;Clark CD;Pawley S;Atkinson N;Fowler AC
最近的代用测量表明，现代冰盖下的冰下湖泊定期储存和释放大量的水，提供了一个重要的，但知之甚少的影响当代冰动力学和质量平衡。这是因为缺乏对湖泊排水如何开始和进行的直接观察。在这里，我们提出的物理证据的机制和几何形状的湖泊排水从残留冰下湖泊的发现形成于末次冰期在加拿大。这些古冰下湖泊由浅（<10米）的水透镜体组成，位于冰流横向的山脊后面。我们发现，湖泊定期排水通过渠道切入床基板（运河）。运河有时倾向于成为eskers，代表了最后一次大规模湖泊爆发的沉积印记。冰下湖泊和河道保存在冰川线理之上，表明冰下水系的长期重组和与冰流的耦合。 由于缺乏直接观测，我们对冰下湖泊排水事件的了解受到限制。在这里，作者使用探地雷达来识别残留的冰下湖泊，并推断排水机制的地貌特征的基础上。
Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow. Our understanding of subglacial lake drainage events is limited by a lack of direct observations. Here, the authors use ground penetrating radar to identify a relict subglacial lake and infer drainage mechanisms based on geomorphological features.