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Hummock corridors in the south-central sector of the Fennoscandian ice sheet, morphometry and pattern

Journal article
Authors Gustaf Peterson
Mark D. Johnson
Published in Earth Surface Processes and Landforms
Volume 43
Issue 4
Pages 919-929
ISSN 0197-9337
Publication year 2018
Published at Department of Earth Sciences
Pages 919-929
Language en
Links dx.doi.org/10.1002/esp.4294
Keywords hummock corridors, glaciofluvial corridors, fennoscandian ice sheet, morphometry, tunnel valleys, subglacial meltwater flow, tunnel valleys, northwest-territories, ribbed, moraine, lake drainage, beneath, deglaciation, genesis, sweden, melt, Physical Geography, Geology
Subject categories Earth and Related Environmental Sciences

Abstract

Subglacial conditions strongly influence the flow of ice-sheets, in part due to the availability of melt water. Contemporary ice sheets are retreating and are affected by increased melting as climate warms. The south Swedish uplands (SSU) were deglaciated during the relatively warm BOlling-AllerOd interval, and by studying the glacial landforms there it is possible to increase the understanding of the subglacial environment during this period of warming. Across the study area, vast tracts of hummocks have long been recognized. However, recent mapping shows a pattern of elongated zones of hummocks radially oriented, hereafter referred to as hummock corridors'. Morphometric parameters were measured on the hummock corridors using a 2m horizontal resolution digital elevation model. Corridor width varies between 0.2 and 4.9km and their length between 1.5 and 11.8km. A majority of hummock corridors are incised in drumlinised till surfaces. The pattern of hummock corridors shows a clear relation to the overall ice-flow. Further, hummock corridors do not follow topographic gradients, and in at least one place an esker overlies hummocks on the corridor floor. The lateral spacing of hummock corridors and corridor morphology are similar to tunnel valleys, eskers and glaciofluvial corridors reported elsewhere. Such relationships support a subglacial genesis of the corridors in the SSU by water driven by the subglacial hydraulic gradient and that hummock corridors are forms that can be identified as tunnel valleys and glaciofluvial corridors (GFC). Ages were assigned to hummock-corridor cross-sections from a deglacial reconstruction of the Fennoscandian Ice Sheet. By comparing the frequency of corridors per age interval with climate variations from a Greenland ice core, we hypothesize that an increase in the number of corridors is related to the BOlling-AllerOd warming, indicating a higher rate of delivery of surface melt water to the bed at this time. Copyright (c) 2017 John Wiley & Sons, Ltd.

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