Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

Abstract. Understanding the retreat behaviour of past marine-based ice sheets provides vital context for accurate assessments of the present stability and long-term response of contemporary polar ice sheets to climate and oceanic warming. Here new multibeam swath bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process dynamics associated with deglaciation of the Celtic ice sheet within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream and the retreat of outlet glaciers draining the adjacent, terrestrially based ice cap centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet readvances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and which dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the readvancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short timescales across marine sectors of the Greenland and Antarctic ice sheets.

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Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

Earth Surface Dynamics Discussions ◽

10.5194/esurfd-1-277-2013 ◽

2013 ◽

Vol 1 (1) ◽

pp. 277-309

Author(s):

H. Patton ◽

A. Hubbard ◽

T. Bradwell ◽

N. F. Glasser ◽

M. J. Hambrey ◽

...

Keyword(s):

Sea Ice ◽

Ice Sheets ◽

Ice Sheet ◽

Irish Sea ◽

Swath Bathymetry ◽

Ice Stream ◽

Non Linear ◽

Polar Ice Sheets ◽

The Irish Sea ◽

Short Time

Abstract. Understanding the retreat behaviour of past marine-ice sheets provides vital context to accurate assessment of the present stability and long-term response of contemporary polar-ice sheets to climate and oceanic warming. Here new multibeam swath-bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process-dynamics associated with deglaciation of the British-Celtic Ice Sheet (BCIS) within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream, the largest draining the BCIS, and the retreat of outlet glaciers draining the adjacent, terrestrially based ice sheet centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet re-advances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice-divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the re-advancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short-time scales across marine-sectors of the Greenland and Antarctic ice sheets.

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Ice-marginal sedimentation associated with the Late Devensian Welsh Ice Cap and the Irish Sea Ice Stream: Tonfanau, West Wales

Proceedings of the Geologists Association ◽

10.1016/j.pgeola.2009.10.004 ◽

2009 ◽

Vol 120 (4) ◽

pp. 256-274 ◽

Cited By ~ 10

Author(s):

Henry Patton ◽

Michael J. Hambrey

Keyword(s):

Sea Ice ◽

Irish Sea ◽

Ice Cap ◽

Ice Stream ◽

The Irish Sea

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Maximum extent and readvance dynamics of the Irish Sea Ice Stream and Irish Sea Glacier since the Last Glacial Maximum

Journal of Quaternary Science ◽

10.1002/jqs.3313 ◽

2021 ◽

Author(s):

J. D. Scourse ◽

R. C. Chiverrell ◽

R. K. Smedley ◽

D. Small ◽

M. J. Burke ◽

...

Keyword(s):

Sea Ice ◽

Last Glacial Maximum ◽

Glacial Maximum ◽

Irish Sea ◽

Maximum Extent ◽

Last Glacial ◽

Ice Stream ◽

The Irish Sea ◽

The Last Glacial Maximum ◽

The Last Glacial

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Late Weichselian Potholes Near Wolverhampton, England

Journal of Glaciology ◽

10.1017/s002214300002685x ◽

1970 ◽

Vol 9 (55) ◽

pp. 125-133 ◽

Cited By ~ 6

Author(s):

Alan V. Morgan

Keyword(s):

Sea Ice ◽

Ice Sheet ◽

Narrow Channel ◽

Irish Sea ◽

Late Weichselian ◽

The Irish Sea ◽

Sand And Gravel ◽

Glacial Streams

Abstract Three potholes and a narrow channel cut into bedrock in a side-hill position were observed beneath an Irish Sea till west of Wolverhampton, England. The potholes and the channel are believed to have been cut by subglacial or latero-glacial streams flowing beneath or immediately beside the Irish Sea ice sheet. They were later choked by sand and gravel from this ice sheet and capped by till which ended the glaciofluvial deposition. Deposits below and above the till have been 14C dated at 30 655 and 13 490 years B.P. at localities between 13 and 27 km north of the trench section described.

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Ice-stream flow switching by up-ice propagation of instabilities along glacial marginal troughs

The Cryosphere ◽

10.5194/tc-13-981-2019 ◽

2019 ◽

Vol 13 (3) ◽

pp. 981-996 ◽

Cited By ~ 2

Author(s):

Etienne Brouard ◽

Patrick Lajeunesse

Keyword(s):

Stream Flow ◽

Ice Sheets ◽

Ice Sheet ◽

Driving Mechanism ◽

Stream Networks ◽

Ice Streams ◽

Swath Bathymetry ◽

Ice Stream ◽

Global Sea Level ◽

Flow Switch

Abstract. Ice-stream networks constitute the arteries of ice sheets through which large volumes of glacial ice are rapidly delivered from the continent to the ocean. Modifications in ice-stream networks have a major impact on ice sheet mass balance and global sea level. Reorganizations in the drainage network of ice streams have been reported in both modern and paleo-ice sheets and usually result in ice streams switching their trajectory and/or shutting down. While some hypotheses for the reorganization of ice streams have been proposed, the mechanisms that control the switching of ice streams remain poorly understood and documented. Here, we interpret a flow switch in an ice-stream system that occurred prior to the last glaciation on the northeastern Baffin Island shelf (Arctic Canada) through glacial erosion of a marginal trough, i.e., deep parallel-to-coast bedrock moats located up-ice of a cross-shelf trough. Shelf geomorphology imaged by high-resolution swath bathymetry and seismo-stratigraphic data in the area indicate the extension of ice streams from Scott and Hecla & Griper troughs towards the interior of the Laurentide Ice Sheet. Up-ice propagation of ice streams through a marginal trough is interpreted to have led to the piracy of the neighboring ice catchment that in turn induced an adjacent ice-stream flow switch and shutdown. These results suggest that competition for ice discharge between the two ice streams, which implies piracy of ice drainage basins via marginal troughs, was the driving mechanism behind ice flow switching. In turn, the enlargement of the ice catchment by piracy increased the volume and discharge of Scott Ice Stream, allowing it to erode deeper and flow farther on the continental shelf. Similar trough systems observed on many other glaciated continental shelves may be the product of such competition for ice discharge between catchments.

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