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Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

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  • Kelly A. Hogan, British Antarctic Survey, University of New Hampshire
  • ,
  • Martin Jakobsson, Stockholm University
  • ,
  • Larry Mayer, University of New Hampshire
  • ,
  • Brendan T. Reilly, Oregon State University
  • ,
  • Anne E. Jennings, University of Colorado, Boulder, CO
  • ,
  • Joseph S. Stoner, Oregon State University
  • ,
  • Tove Nielsen, Geological Survey of Denmark and Greenland
  • ,
  • Katrine J. Andresen
  • Egon Nørmark
  • Katrien A. Heirman, Geological Survey of Denmark and Greenland, Netherlands Organisation for Applied Scientific Research (TNO)
  • ,
  • Elina Kamla, Geological Survey of Denmark and Greenland, Ramboll Group AS
  • ,
  • Kevin Jerram, University of New Hampshire
  • ,
  • Christian Stranne, Stockholm University
  • ,
  • Alan Mix, Oregon State University

Petermann Fjord is a deep ( > 1000 m) fjord that incises the coastline of north-west Greenland and was carved by an expanded Petermann Glacier, one of the six largest outlet glaciers draining the modern Greenland Ice Sheet (GrIS). Between 5 and 70m of unconsolidated glacigenic material infills in the fjord and adjacent Nares Strait, deposited as the Petermann and Nares Strait ice streams retreated through the area after the Last Glacial Maximum. We have investigated the deglacial deposits using seismic stratigraphic techniques and have correlated our results with high-resolution bathymetric data and core lithofacies. We identify six seismoacoustic facies in more than 3500 line kilometres of subbottom and seismic-reflection profiles throughout the fjord, Hall Basin and Kennedy Channel. Seismo-acoustic facies relate to bedrock or till surfaces (Facies I), subglacial deposition (Facies II), deposition from meltwater plumes and icebergs in quiescent glacimarine conditions (Facies III, IV), deposition at grounded ice margins during stillstands in retreat (grounding-zone wedges; Facies V) and the redeposition of material downslope (Facies IV). These sediment units represent the total volume of glacial sediment delivered to the mapped marine environment during retreat. We calculate a glacial sediment flux for the former Petermann ice stream as 1080-1420m3 a-1 per metre of ice stream width and an average deglacial erosion rate for the basin of 0.29-0.34mma-1. Our deglacial erosion rates are consistent with results from Antarctic Peninsula fjord systems but are several times lower than values for other modern GrIS catchments. This difference is attributed to fact that large volumes of surface water do not access the bed in the Petermann system, and we conclude that glacial erosion is limited to areas overridden by streaming ice in this large outlet glacier setting. Erosion rates are also presented for two phases of ice retreat and confirm that there is significant variation in rates over a glacial- deglacial transition. Our new glacial sediment fluxes and erosion rates show that the Petermann ice stream was approximately as efficient as the palaeo-Jakobshavn Isbræ at eroding, transporting and delivering sediment to its margin during early deglaciation.

Original languageEnglish
Pages (from-to)261-286
Number of pages26
Publication statusPublished - 2020

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