TY - JOUR
T1 - Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland
AU - Hogan, Kelly A.
AU - Jakobsson, Martin
AU - Mayer, Larry
AU - Reilly, Brendan T.
AU - Jennings, Anne E.
AU - Stoner, Joseph S.
AU - Nielsen, Tove
AU - Andresen, Katrine J.
AU - Nørmark, Egon
AU - Heirmann, Katrien A.
AU - Kamla, Elina
AU - Jerram, Kevin
AU - Stranne, Christian
AU - Mix, Alan
N1 - Funding Information:
Financial support. This research has been supported by the Na-
Funding Information:
Acknowledgements. The Petermann 2015 Expedition was supported by the US NSF Polar Programs, NASA, UNAVCO, CH2M Polar Field Services (Jessy Jenkins), Polar Geospatial Center, the Swedish Polar Research Secretariat, and the Swedish Maritime Administration. We thank the Federal Institute for Geosciences and Natural Resources (BGR), Hanover, for giving us permission to use the 2001 seismic-reflection profiles in this study. We also thank Geocenter Danmark, who supported the inclusion of multichannel seismic data acquisition during the Petermann 2015 Expedition and Per Trinhammer for his help acquiring these data. We thank Neil Arnold for the useful discussions about Greenland glaciology and hydrology.
Publisher Copyright:
© Author(s) 2020.
PY - 2020/1/28
Y1 - 2020/1/28
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85078798751&partnerID=8YFLogxK
U2 - 10.5194/tc-14-261-2020
DO - 10.5194/tc-14-261-2020
M3 - Article
VL - 14
SP - 261
EP - 286
JO - Cryosphere
JF - Cryosphere
SN - 1994-0416
IS - 1
ER -