Early deglaciation of the British-Irish Ice Sheet on the Atlantic shelf northwest of Ireland driven by glacioisostatic depression and high relative sea level

Colm OCofaigh, Kasper Weilbach, Jerry Lloyd, S. Benetti, Louise Callard, Catriona Purcell, Richard Chiverell, Paul Dunlop, Margot Saher, Stephen Livingstone, Karen Van Landeghem, Steven Moreton, Chris Clark, Derek Fabel

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Understanding the triggers and pace of marine-based ice sheet decay is critical for constraining the future mass loss and dynamic behaviour of marine-based sectors of the large polar ice sheets in Greenland and Antarctica. Numerical models which seek to predict this behaviour need to be calibrated against data from both contemporary and palaeo-ice sheets, and the latter requires accurate reconstruction of former ice sheet extent, dynamics and timing. Marine geophysics, sediment cores, benthic foraminiferal assemblages and radiocarbon dating are used to reconstruct the extent of the last British-Irish Ice Sheet (BIIS), and the timing and style of its retreat on the Atlantic shelf northwest of Ireland. Shelf edge moraines and subglacial till recovered in cores from the outer continental shelf are dated to younger than 26.3 ka cal BP and indicate an extensive ice sheet at the Last Glacial Maximum (LGM) that was grounded to the shelf edge. Nested arcuate moraines record the subsequent episodic retreat of the ice sheet across the shelf. Lithofacies and associated foraminiferal assemblages demonstrate that this retreat occurred in a glacimarine environment as a grounded tidewater margin and that high relative sea level and cold waters prevailed during retreat. Radiocarbon dates indicate that the timing of initial ice sheet retreat from the shelf edge occurred in the interval between 26.3 and 24.8 ka cal BP, during the period of minimum global eustatic sea level, and that the ice sheet had retreated to the mid-shelf by 24.8 ka cal BP. The ‘Donegal Bay Moraine’, a large moraine at the mouth of Donegal Bay, records a major stillstand and readvance of the ice sheet during deglaciation between 20.2 and 17.9 ka cal BP. Estimated retreat rates of 5.5–35 m a −1 across the shelf demonstrate that retreat was slow. It is noteworthy that retreat was initiated in the absence of ocean warming and when eustatic sea level was at a minimum. The sea-level rise that initiated deglaciation from the shelf edge therefore, is inferred to have been a product of local glacio-isostatic crustal depression rather than external forcing. This demonstrates that marine-based sectors of ice sheets can trigger their own demise internally through glacio-isostatic adjustment and it provides an explanation for the early retreat of the BIIS on the Atlantic shelf during the global LGM (gLGM).

LanguageEnglish
Pages76-96
Number of pages21
JournalQuaternary Science Reviews
Volume208
Early online date15 Feb 2019
DOIs
Publication statusPublished - 15 Mar 2019

Fingerprint

deglaciation
Ireland
sea level
ice sheet
ice
shelf break
Antarctica
reconstruction
moraine
Last Glacial Maximum
water
Retreat
Sea Level
geophysics
radiocarbon dating
Greenland
lithofacies
cold water
sediment core
benthos

Keywords

  • British-Irish ice sheet
  • Continental shelf
  • Glacimarine
  • Ice sheet retreat
  • Ireland
  • Last glacial maximum
  • Moraines
  • Radiocarbon dating

Cite this

OCofaigh, Colm ; Weilbach, Kasper ; Lloyd, Jerry ; Benetti, S. ; Callard, Louise ; Purcell, Catriona ; Chiverell, Richard ; Dunlop, Paul ; Saher, Margot ; Livingstone, Stephen ; Van Landeghem, Karen ; Moreton, Steven ; Clark, Chris ; Fabel, Derek. / Early deglaciation of the British-Irish Ice Sheet on the Atlantic shelf northwest of Ireland driven by glacioisostatic depression and high relative sea level. 2019 ; Vol. 208. pp. 76-96.
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OCofaigh, C, Weilbach, K, Lloyd, J, Benetti, S, Callard, L, Purcell, C, Chiverell, R, Dunlop, P, Saher, M, Livingstone, S, Van Landeghem, K, Moreton, S, Clark, C & Fabel, D 2019, 'Early deglaciation of the British-Irish Ice Sheet on the Atlantic shelf northwest of Ireland driven by glacioisostatic depression and high relative sea level', vol. 208, pp. 76-96. https://doi.org/10.1016/j.quascirev.2018.12.022

Early deglaciation of the British-Irish Ice Sheet on the Atlantic shelf northwest of Ireland driven by glacioisostatic depression and high relative sea level. / OCofaigh, Colm; Weilbach, Kasper; Lloyd, Jerry; Benetti, S.; Callard, Louise; Purcell, Catriona; Chiverell, Richard; Dunlop, Paul; Saher, Margot; Livingstone, Stephen; Van Landeghem, Karen; Moreton, Steven; Clark, Chris; Fabel, Derek.

Vol. 208, 15.03.2019, p. 76-96.

Research output: Contribution to journalArticle

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AU - OCofaigh, Colm

AU - Weilbach, Kasper

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AU - Benetti, S.

AU - Callard, Louise

AU - Purcell, Catriona

AU - Chiverell, Richard

AU - Dunlop, Paul

AU - Saher, Margot

AU - Livingstone, Stephen

AU - Van Landeghem, Karen

AU - Moreton, Steven

AU - Clark, Chris

AU - Fabel, Derek

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N2 - Understanding the triggers and pace of marine-based ice sheet decay is critical for constraining the future mass loss and dynamic behaviour of marine-based sectors of the large polar ice sheets in Greenland and Antarctica. Numerical models which seek to predict this behaviour need to be calibrated against data from both contemporary and palaeo-ice sheets, and the latter requires accurate reconstruction of former ice sheet extent, dynamics and timing. Marine geophysics, sediment cores, benthic foraminiferal assemblages and radiocarbon dating are used to reconstruct the extent of the last British-Irish Ice Sheet (BIIS), and the timing and style of its retreat on the Atlantic shelf northwest of Ireland. Shelf edge moraines and subglacial till recovered in cores from the outer continental shelf are dated to younger than 26.3 ka cal BP and indicate an extensive ice sheet at the Last Glacial Maximum (LGM) that was grounded to the shelf edge. Nested arcuate moraines record the subsequent episodic retreat of the ice sheet across the shelf. Lithofacies and associated foraminiferal assemblages demonstrate that this retreat occurred in a glacimarine environment as a grounded tidewater margin and that high relative sea level and cold waters prevailed during retreat. Radiocarbon dates indicate that the timing of initial ice sheet retreat from the shelf edge occurred in the interval between 26.3 and 24.8 ka cal BP, during the period of minimum global eustatic sea level, and that the ice sheet had retreated to the mid-shelf by 24.8 ka cal BP. The ‘Donegal Bay Moraine’, a large moraine at the mouth of Donegal Bay, records a major stillstand and readvance of the ice sheet during deglaciation between 20.2 and 17.9 ka cal BP. Estimated retreat rates of 5.5–35 m a −1 across the shelf demonstrate that retreat was slow. It is noteworthy that retreat was initiated in the absence of ocean warming and when eustatic sea level was at a minimum. The sea-level rise that initiated deglaciation from the shelf edge therefore, is inferred to have been a product of local glacio-isostatic crustal depression rather than external forcing. This demonstrates that marine-based sectors of ice sheets can trigger their own demise internally through glacio-isostatic adjustment and it provides an explanation for the early retreat of the BIIS on the Atlantic shelf during the global LGM (gLGM).

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