Shelf-break glaciation and an extensive ice shelf beyond northwest Greenland at the Last Glacial Maximum

IF 2.6 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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Abstract

The analysis of seafloor glacial landforms can provide important constraints on the past behaviour of ice sheets, including their extent at the Last Glacial Maximum and the controls on their subsequent retreat. The continental shelf and slope offshore of northwest Greenland have been sparsely surveyed, however, limiting our understanding of ice sheet extent and dynamics in this sector during the pre-satellite era. Here we use newly acquired high-resolution geophysical data to map and interpret the distribution of glacial landforms across the hitherto unexplored banks of northern Melville Bay and the adjacent slope and deep-sea basin. In contrast to previous conceptual models, our seafloor observations suggest that shelf-break glaciation was attained along the entire northwest Greenland margin at the Last Glacial Maximum, including beyond the shallow banks. The landforms that we map on the continental slope provide strong support for the existence of an ice shelf spanning northern Baffin Bay. Sub-ice shelf keel scours in water depths of down to 1220 m reveal that this ice shelf was at least 1100 m thick at its grounding zone. The orientation of sub-ice shelf landforms suggests that the ice shelf was fed mainly by the supply of ice to northern Baffin Bay from the Lancaster Sound Ice Stream of the Canadian Arctic Archipelago. The Baffin Bay ice shelf buttressed several large ice streams of the Greenland, Innuitian and Laurentide ice sheets at the Last Glacial Maximum, and its break-up may have contributed to instigating the deglacial retreat of these ice streams from the shelf edge.

末次冰期格陵兰岛西北部的断裂冰川和大面积冰架
对海底冰川地貌的分析可以为冰原过去的行为提供重要的制约因素,包括冰原在末次冰川最盛时期的范围以及对其随后消退的控制。然而,对格陵兰岛西北部近海大陆架和斜坡的勘测很少,这限制了我们对前卫星时代该地区冰盖范围和动态的了解。在这里,我们利用新获得的高分辨率地球物理数据,绘制并解释了迄今为止尚未勘探的梅尔维尔湾北部两岸冰川地貌的分布情况,以及邻近的斜坡和深海盆地。与之前的概念模型不同,我们的海底观测结果表明,在末次冰川极盛时期,整个格陵兰岛西北边缘都出现了陆架断裂冰川作用,包括浅滩以外的地区。我们在大陆坡上绘制的地貌为横跨巴芬湾北部的冰架的存在提供了有力的支持。在水深达 1220 米的冰架下龙骨冲刷显示,该冰架的着陆区至少有 1100 米厚。冰架下地貌的走向表明,该冰架主要由加拿大北极群岛兰开斯特湾冰流向巴芬湾北部提供的冰供给。巴芬湾冰架在末次冰川极盛时期支撑着格陵兰、因努伊特和劳伦泰德冰原的几大冰流,它的断裂可能促使这些冰流从冰架边缘退缩。
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来源期刊
Marine Geology
Marine Geology 地学-地球科学综合
CiteScore
6.10
自引率
6.90%
发文量
175
审稿时长
21.9 weeks
期刊介绍: Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.
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