Rapid retreat of a Scandinavian marine outlet glacier in response to warming at the last glacial termination

Åkesson, Henning; Gyllencreutz, Richard; Mangerud, Jan; Svendsen, John Inge; Nick, F. M.; Nisancioglu, Kerim H.

doi:10.1016/j.quascirev.2020.106645

Cited by 4 publications

(5 citation statements)

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“…2016, 2019; Åkesson et al . 2020). An ice‐sheet sector less sensitive to climate changes may have facilitated the prolonged and stable maximum YD ice‐sheet position inferred for Mid‐Norway in this study, including the delayed initial demise.…”

Section: Discussionmentioning

confidence: 99%

Palaeolake sediment records reveal a mid‐ to late Younger Dryas ice‐sheet maximum in Mid‐Norway

Høgaas

Larsson

Klug

et al. 2021

Boreas

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We present a revised chronology of the Scandinavian Ice Sheet’s glacial maximum during the Younger Dryas (Tautra event) in Mid‐Norway. Sediment records from palaeolakes near Leksvik show the occurrence of thick, laminated silt units with numerous dropstones between organic‐rich units and indicate that a proglacial lake was dammed between the Tautra ice margin and a local spillway. Ash beds and several radiocarbon‐dated plant macrofossil samples from corresponding stratigraphical sequences in different basins provide robust chronological constraints for the timing and duration of the proglacial lake and, consequently, the Tautra event. The existing chronological constraints on the Tautra event suggest that the glacial episode occurred at 12.9–12.6 ka. Our new chronology indicates that the Younger Dryas ice‐sheet re‐advance culminated close to 12.1 cal. ka BP, maintained this position for a maximum of 700 years and started retreating inland at c. 11.4 cal. ka BP. Our revised age for retreat from the Younger Dryas glacial maximum thus differs from the existing deglaciation chronology by approximately a thousand years, and hints at a similar late Younger Dryas glacial maximum throughout most of southern Norway.

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Section: Discussionmentioning

confidence: 99%

Palaeolake sediment records reveal a mid‐ to late Younger Dryas ice‐sheet maximum in Mid‐Norway

Høgaas

Larsson

Klug

et al. 2021

Boreas

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“…The setup represents a medium-sized fjord-glacier system, which has similar dimensions and dynamics as, for example, the present-day Alison glacier in NW Greenland, where the fjord width is about 5 km, water depth is around 500 m, and observed ice discharge has increased from ∼ 4 to ∼ 8 Gt yr −1 in the past 20 yr (Mouginot et al, 2019). It is furthermore broadly representative of outlet glaciers from the Fennoscandian Ice Sheet during the last glacial, such as the Hardangerfjorden glacier (Mangerud et al, 2013;Åkesson et al, 2020).…”

Section: Reference Glaciermentioning

confidence: 93%

“…While remotely sensed observations of ice dynamics over the past decades exist, the recent retreat in Greenland and elsewhere over this period is too short to allow for a complete assessment of geometry-glacier interactions (Carr et al, 2013;Catania et al, 2018;Bunce et al, 2018). In contrast, on paleo-timescales, retreat has occurred over large distances, but the temporal resolution of geomorphological studies is limited by the available geological data, and key information is missing to discern different drivers of glacier retreat (Briner et al, 2009;Åkesson et al, 2020). Meanwhile, numerical studies that can address these issues have so far mostly used width-and depth-integrated flow line models, which carry many assumptions that do not hold in some settings (Nick et al, 2009;Åkesson et al, 2018b;Steiger et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Geometric controls of tidewater glacier dynamics

et al. 2022

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Abstract. Retreat of marine outlet glaciers often initiates depletion of inland ice through dynamic adjustments of the upstream glacier. The local topography of a fjord may promote or inhibit such retreat, and therefore fjord geometry constitutes a critical control on ice sheet mass balance. To quantify the processes of ice–topography interactions and enhance the understanding of the dynamics involved, we analyze a multitude of topographic fjord settings and scenarios using the Ice-sheet and Sea-level System Model (ISSM). We systematically study glacier retreat through a variety of artificial fjord geometries and quantify the modeled dynamics directly in relation to topographic features. We find that retreat in an upstream-widening or upstream-deepening fjord does not necessarily promote retreat, as suggested by previous studies. Conversely, it may stabilize a glacier because converging ice flow towards a constriction enhances lateral and basal shear stress gradients. An upstream-narrowing or upstream-shoaling fjord, in turn, may promote retreat since fjord walls or bed provide little stability to the glacier where ice flow diverges. Furthermore, we identify distinct quantitative relationships directly linking grounding line discharge and retreat rate to fjord topography and transfer these results to a long-term study of the retreat of Jakobshavn Isbræ. These findings offer new perspectives on ice–topography interactions and give guidance to an ad hoc assessment of future topographically induced ice loss based on knowledge of the upstream fjord geometry.

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“…The setup represents a medium sized fjord-glacier system, which has similar dimensions and dynamics as, for example, the present-day Alison glacier in NW Greenland, where the fjord width is about 5 km, water depth is around 500 m and observed ice discharge has increased from ∼ 4 to ∼ 8 Gt yr −1 in the past 20 yrs (Mouginot et al, 2019). It is furthermore broadly representative of outlet glaciers from the Fennoscandian ice sheet during the last glacial, such as the Hardangerfjorden glacier (Mangerud et al, 2013;Åkesson et al, 2020).…”

Section: Reference Glaciermentioning

confidence: 96%

“…ice dynamics over the past decades exist, the recent retreat in Greenland and elsewhere over this period is too short to allow for a complete assessment of geometry-glacier interactions (Carr et al, 2013;Catania et al, 2018;Bunce et al, 2018). In contrast, on paleo-time scales, retreat has occurred over large distances, but the temporal resolution of geomorphological studies is limited by the available geological data and key information is missing to discern different drivers of glacier retreat (Briner et al, 2009;Åkesson et al, 2020). Meanwhile, numerical studies that can address these issues have so far mostly used widthand depth-integrated flowline models, which carry many assumptions that do not hold in some settings (Nick et al, 2009;Åkesson et al, 2018b;Steiger et al, 2018).…”

mentioning

confidence: 99%

Geometric Controls of Tidewater Glacier Dynamics

Frank

Åkesson

Fleurian

et al. 2021

Preprint

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Abstract. Retreat of marine outlet glaciers often initiates depletion of inland ice through dynamic adjustments of the upstream glacier. The local topography of a fjord may promote or inhibit such retreat, and therefore fjord geometry constitutes a critical control on ice sheet mass balance. To quantify the processes of ice-topography interactions and enhance the understanding of the dynamics involved, we analyze a multitude of topographic fjord settings and scenarios using the Ice-sheet and Sea-level System Model (ISSM). We systematically study glacier retreat through a variety of artificial fjord geometries and quantify the modeled dynamics directly in relation to topographic features. We find that retreat in an upstream widening or deepening fjord does not necessarily promote retreat, but conversely, may stabilize a glacier because converging ice flow towards a constriction enhances lateral shear. An upstream narrowing or shoaling fjord, in turn, may promote retreat since fjord walls or bed provide little stability to the glacier where ice flow diverges. Furthermore, we identify distinct quantitative relationships directly linking grounding line discharge and retreat rate to fjord topography, and transfer these results to a long-term study of the retreat of Jakobshavn Isbræ. These findings offer new perspectives on ice-topography interactions, and give guidance to an ad-hoc assessment of future topographically induced ice loss based on knowledge of the upstream fjord geometry.

show abstract

Rapid retreat of a Scandinavian marine outlet glacier in response to warming at the last glacial termination

Cited by 4 publications

References 80 publications

Palaeolake sediment records reveal a mid‐ to late Younger Dryas ice‐sheet maximum in Mid‐Norway

Palaeolake sediment records reveal a mid‐ to late Younger Dryas ice‐sheet maximum in Mid‐Norway

Geometric controls of tidewater glacier dynamics

Geometric Controls of Tidewater Glacier Dynamics

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