Greenwood Sarah L, Simkins Lauren M, Winsborrow Monica C M, Bjarnadóttir Lilja R
Department of Geological Sciences, Stockholm University, 10691 Stockholm, Sweden.
Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA.
Sci Adv. 2021 Jan 13;7(3). doi: 10.1126/sciadv.abb6291. Print 2021 Jan.
Projections of ice sheet behavior hinge on how ice flow velocity evolves and the extent to which marine-based grounding lines are stable. Ice flow and grounding line retreat are variably governed by the coupling between the ice and underlying terrain. We ask to what degree catchment-scale bed characteristics determine ice flow and retreat, drawing on paleo-ice sheet landform imprints from 99 sites on continental shelves worldwide. We find that topographic setting has broadly steered ice flow and that the bed slope favors particular styles of retreat. However, we find exceptions to accepted "rules" of behavior: Regional topographic highs are not always an impediment to fast ice flow, retreat may proceed in a controlled, steady manner on reverse slopes and, unexpectedly, the occurrence of ice streaming is not favored on a particular geological substrate. Furthermore, once grounding line retreat is under way, readvance is rarely observed regardless of regional bed characteristics.
冰盖行为的预测取决于冰流速度如何演变以及海洋型接地线的稳定程度。冰流和接地线后退受冰与下伏地形之间耦合作用的不同程度控制。我们利用全球大陆架上99个地点的古冰盖地貌印记，探讨集水区尺度的床面特征在多大程度上决定冰流和后退。我们发现地形背景大致上引导了冰流，且床面坡度有利于特定的后退方式。然而，我们发现了公认行为“规则”的例外情况：区域地形高处并不总是快速冰流的障碍，后退可能在反向斜坡上以可控、稳定的方式进行，而且出乎意料的是，特定地质基底上并不利于出现冰流。此外，一旦接地线开始后退，无论区域床面特征如何，很少观察到再前进的情况。
