Ice-stream flow switching during deglaciation of the southwestern Barents Sea
Ice-stream flow switching during deglaciation of the southwestern Barents Sea
复制标题
巴伦支海西南部冰消过程中的冰流流量转换
DOI：
10.1130/b30416.1
复制
发表时间：
2012
影响因子：
4.9
通讯作者：
K. Andreassen
中科院分区：
文献类型：
--
作者：
M. Winsborrow;C. Stokes;K. Andreassen
冰流主导着大陆冰盖的排放。最近的观察和重建表明，它们的流动轨迹（流动切换）可以在相对较短的时间尺度内发生大规模重组。然而，这种行为的潜在原因，以及它们在多大程度上是可预测的，却鲜为人知。本文记录了巴伦支海西南部威奇塞利期冰消期冰流转换的一个重要事件，并探讨了其成因的各种假设。区域测深数据显示，两个具有相似、相邻、地形受限源区的冰流在外大陆架上有着非常不同的轨迹和动力学。在Weichselian晚期极大期，Hakjerringdjupet冰流沿Hakjerringdjupet交叉陆架槽向西流动，Soroya槽冰流向北流入ingoyjupet，形成Bjornoyrenna冰流的一条支流。Hakjerringdjupet冰流最初的退缩是迅速的，但有断断续续的搁浅期。当它退到更高、更粗糙的内陆架地形上时，我们推断冰的速度会减少，后退的速度也会急剧下降，这是由嵌套的退潮冰碛序列所记录的。在此之后（可能是作为回应），我们认为Fugloybanken上的相邻瓣存在短暂的浪涌/读取。相比之下，相邻的索罗亚海槽冰流在整个消冰期保持活跃，然后迅速退缩，没有静止或前进。我们认为，冰流的不同退缩历史是由河床地形/水深的变化决定的，这些变化调节了地面线对海平面变化的响应。这种机制很可能是对南极和格陵兰的海洋冰流和出口冰川的长期行为的重要控制，并建议应优先收集其冰下地形的数据。
Ice streams dominate the discharge of continental ice sheets. Recent observations and reconstructions have revealed that large-scale reorganizations in their flow trajectory (flow switching) can occur over relatively short time scales. However, the underlying causes of such behavior, and the extent to which they are predictable, are poorly known. This paper documents a major episode of ice-stream flow switching during the late Weichselian deglaciation of the southwestern Barents Sea and explores various hypotheses for its causation. Regional bathymetric data show that two ice streams that had similar, adjoining, topographically constrained source areas had very different trajectories and dynamics on the outer shelf. At the late Weichselian maximum, the Hakjerringdjupet ice stream flowed westward along the cross-shelf trough of Hakjerringdjupet, while the Soroya Trough ice stream flowed northward into Ingoydjupet, forming a tributary of the Bjornoyrenna ice stream. Initial retreat of the Hakjerringdjupet ice stream was rapid but with episodic periods of grounding. As it retreated onto the higher, rougher topography of the inner shelf, we infer a reduction in ice velocity and a dramatic decrease in the pace of retreat, as recorded by nested sequences of recessional moraines. Following (and probably in response to) this, we suggest that there was a short-lived surge/readvance of an adjacent lobe onto Fugloybanken. In contrast, the adjacent Soroya Trough ice stream remained active throughout deglaciation, before retreating rapidly, with no stillstands or readvances. We argue that the different retreat histories of the ice streams were determined by variations in bed topography/bathymetry, which modulated the grounding line response to sea-level variation. Such a mechanism is likely to be an important control on the long-term behavior of marine-based ice streams and outlet glaciers in Antarctica and Greenland and suggests that gathering data on their subglacial topography should be a priority.