TY - JOUR

T1 - Ice-stream shutdown during deglaciation

T2 - Evidence from crevasse-squeeze ridges of the Iceland Ice Sheet

AU - Aradóttir, Nína

AU - Benediktsson, Ívar Örn

AU - Ingólfsson, Ólafur

AU - Brynjólfsson, Skafti

AU - Farnsworth, Wesley R.

AU - Benjamínsdóttir, Margrét Mjöll

AU - Ríkharðsdóttir, Lena Björg

N1 - Publisher Copyright: © 2023 John Wiley & Sons Ltd.

PY - 2023

Y1 - 2023

N2 - Both modern and palaeo-ice streams experience shutdown, which has critical implications for their mass balance and influence on relative sea level. Reconstructions of palaeo-ice streams have mainly focused on their phase of active flow and thus less is understood of their shutdown and style of deglaciation. Mapping of streamlined subglacial bedforms (SSBs), including drumlins and mega-scale glacial lineations, in northeast Iceland reveals cross-cutting flow-sets of palaeo-ice streams within the Iceland Ice Sheet (IIS) during and following the last glacial maximum (LGM). Here we map geometrical ridges (linear and reticular) within the Bakkaflói and Þistilfjörður flow-sets and combine the morphological data with sedimentological analyses to increase our understanding of the dynamics of the IIS during deglaciation in northeast Iceland. We interpret the ridges as crevasse-squeeze ridges (CSRs), based on their interconnected network, primary orientation transverse and/or oblique to former ice flow and internal composition of homogenous subglacial till. In both areas, the CSRs are superimposed on the SSBs, indicating that they post-date the SSBs and signify the waning stage of ice streaming associated with the readvance of the IIS during the Younger Dryas period. The preservation of the CSRs suggests ice stagnation following the readvance and ice-stream shutdown. The morphological difference of the CSRs between the flow-sets is taken to indicate different kinematic setting within the ice streams; the linear CSRs in Bakkaflói formed further upstream where extensional forces parallel to ice flow were dominant, whereas the reticular CSRs in Þistilfjörður are more indicative of transverse and longitudinal forces near the terminal zone. Future research reconstructing past ice-sheet behaviour and ice-stream dynamics would benefit from high-resolution bathymetric data from the adjoining shelf as well as enhanced geochronological constraints.

AB - Both modern and palaeo-ice streams experience shutdown, which has critical implications for their mass balance and influence on relative sea level. Reconstructions of palaeo-ice streams have mainly focused on their phase of active flow and thus less is understood of their shutdown and style of deglaciation. Mapping of streamlined subglacial bedforms (SSBs), including drumlins and mega-scale glacial lineations, in northeast Iceland reveals cross-cutting flow-sets of palaeo-ice streams within the Iceland Ice Sheet (IIS) during and following the last glacial maximum (LGM). Here we map geometrical ridges (linear and reticular) within the Bakkaflói and Þistilfjörður flow-sets and combine the morphological data with sedimentological analyses to increase our understanding of the dynamics of the IIS during deglaciation in northeast Iceland. We interpret the ridges as crevasse-squeeze ridges (CSRs), based on their interconnected network, primary orientation transverse and/or oblique to former ice flow and internal composition of homogenous subglacial till. In both areas, the CSRs are superimposed on the SSBs, indicating that they post-date the SSBs and signify the waning stage of ice streaming associated with the readvance of the IIS during the Younger Dryas period. The preservation of the CSRs suggests ice stagnation following the readvance and ice-stream shutdown. The morphological difference of the CSRs between the flow-sets is taken to indicate different kinematic setting within the ice streams; the linear CSRs in Bakkaflói formed further upstream where extensional forces parallel to ice flow were dominant, whereas the reticular CSRs in Þistilfjörður are more indicative of transverse and longitudinal forces near the terminal zone. Future research reconstructing past ice-sheet behaviour and ice-stream dynamics would benefit from high-resolution bathymetric data from the adjoining shelf as well as enhanced geochronological constraints.

KW - crevasse-squeeze ridges

KW - deglaciation

KW - glacial landforms

KW - ice-sheet dynamics

KW - ice-stream shutdown

KW - Iceland Ice Sheet

KW - palaeo-ice stream

U2 - 10.1002/esp.5636

DO - 10.1002/esp.5636

M3 - Journal article

AN - SCOPUS:85161632140

VL - 48

SP - 2412

EP - 2430

JO - Earth Surface Processes and Landforms

JF - Earth Surface Processes and Landforms

SN - 0197-9337

IS - 12

ER -