Marine ice sheet instability and ice shelf buttressing of the Minch Ice Stream, northwest Scotland

Gandy, Niall; Gregoire, Lauren; Ely, Jeremy C.; Clark, Chris D.; Hodgson, David M.; Lee, Victoria; Bradwell, Tom; Ivanovic, Ruza

doi:10.5194/tc-12-3635-2018

Cited by 28 publications

(43 citation statements)

References 70 publications

(106 reference statements)

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“…BISICLES was chosen for its efficient and accurate representation of the dynamics of marine grounded ice sheets and for its process‐representation permitting ice shelf formation, grounding line migration, and ice surface lowering. BISICLES has previously been applied to simulations of both contemporary (e. g., Antarctica , Cornford et al, 2015; Berger et al, 2016) and paleo ice sheets (e.g., The British‐Irish Ice Sheet; Gandy et al, 2018, 2019), as well as to smaller icefields (e.g., Patagonia). The dynamical equations in BISICLES fall into type “L1L2” of hybrid ice sheet modeling approaches (Hindmarsh, 2004), where the longitudinal stresses are treated as depth dependent, and are included in the computation of stresses driving the ice flow (Schoof & Hindmarsh, 2010).…”

Section: Methodsmentioning

confidence: 99%

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Sutherland

Carrivick

Gandy

et al. 2020

Geophysical Research Letters

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Ice-contact proglacial lakes are generally absent from numerical model simulations of glacier evolution, and their effects on ice dynamics and on rates of deglaciation remain poorly quantified. Using the BISICLES ice flow model, we analyzed the effects of an ice-contact lake on the Pukaki Glacier, New Zealand, during recession from the Last Glacial Maximum. The ice-contact lake produced a maximum effect on grounding line recession >4 times further and on ice velocities up to 8 times faster, compared to simulations of a land-terminating glacier forced by the same climate. The lake contributed up to 82% of cumulative grounding line recession and 87% of ice velocity during the first 300 years of the simulations, but those values decreased to just 6% and 37%, respectively, after 5,000 years. Numerical models that ignore lake interactions will, therefore, misrepresent the rate of recession especially during the transition of a land-terminating to a lake-terminating environment. Plain Language Summary Lakes form at the margins of glaciers as meltwater accumulates against hillsides and behind ridges of glacier debris. Lakes at a glacier terminus are known to affect its behavior. However, glaciers terminating into such lakes are usually absent from computer simulations, and the effects of these lakes on the rates of deglaciation and on glacier behavior are poorly quantified. In this study, we tested the effect of a lake on glacier recession under two different scenarios; a land-terminating versus a lake-terminating glacier. We used an ice flow model called BISICLES and applied it to what was once the Pukaki Glacier in New Zealand during the end of the last ice age. We found that the presence of a lake caused the glacier to recede more than 4 times further and it accelerated ice flow by up to 8 times when compared to the same glacier that terminated on land under the same climate. Our simulated lake processes predominantly influenced the glacier over decades to centuries rather than over millennia. We suggest, therefore, that simulations of glacier evolution ignoring glacial lakes will likely misrepresent the timing and rate of recession, especially during the transition from a land-terminating to a lake-terminating environment. Recent observations, both field-based (e.g., Watson et al., 2020) and via satellite imagery (e.g., King et al., 2019), have highlighted the spatiotemporal frequency and magnitude of changes in glacial lakes and the associated glaciers that feed meltwater to them. However, field-based measurements are limited to

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Section: Methodsmentioning

confidence: 99%

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Sutherland

Carrivick

Gandy

et al. 2020

Geophysical Research Letters

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“…The conditions at the ice-bed interface (melting or non-melting), the availability of liquid water and mechanical properties of the till (soft or hard) thus control the processes that can be activated. A simple hydrology scheme has recently been added to BISICLES to allow for the self-generation of ice streams by representing basal sliding with a Coulomb law sensitive to the presence of till water (Gandy et al, 2019). However, this scheme is not included in the version of BISICLES used here.…”

Section: Basal Processesmentioning

confidence: 99%

“…Recently, a simple basal sliding scheme has been added into BISICLES. The scheme uses a Coulomb sliding law sensitive to the presence of till water and is able to simulate well the ice streams of the British-Irish Ice Sheet (Gandy et al, 2019). However, the version of BISICLES we used here does not yet include these processes of basal hydrology that are needed to generate ice streams.…”

Section: Basal Tractionmentioning

confidence: 99%

Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)

2020

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Abstract. Simulating the demise of the Laurentide Ice Sheet covering Hudson Bay in the Early Holocene (10–7 ka) is important for understanding the role of accelerated changes in ice sheet topography and melt in the 8.2 ka event, a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical ice loss and marine interactions could have significantly accelerated the ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past ice sheets. Here, we developed an ice sheet model setup for studying the Laurentide Ice Sheet's Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES ice sheet model, an efficient marine ice sheet model of the latest generation which is capable of refinement to kilometre-scale resolutions and higher-order ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the ice sheet temperature, recent ice sheet reconstructions for developing the topography of the region and ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the ice sheet, and the associated meltwater pulse has realistic timing. Furthermore, the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representations of the glacial dynamics and marine interactions are key for correctly simulating the pattern of Early Holocene ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.

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“…equilibrium simulations) run at 1-ka intervals for 26-21 ka and 500-year intervals for 21-0 ka. They are the same simulations used and described in more detail by Morris et al (2018), Swindles et al (2018) and Gandy et al (2018). The snapshots represent a refinement from earlier HadCM3 simulations (Singarayer et al, 2011;Singarayer and Valdes, 2010), and have been updated according to boundary conditions provided for the Palaeoclimate Model Intercomparison Project Phase 4 protocol for simulations of the last deglaciation (version 1; Ivanovic et al, 2016), using the ICE-6G_c reconstruction (Peltier et al, 2015).…”

Section: Surface Mass Balance and Climate Inputsmentioning

confidence: 99%

“…They showed that the movement of the grounding line, overall mass loss and evolution of fast-flowing ice streams are all sensitive to increasing the mesh resolution and features in bed geometry (Cornford et al, 2015;Lee et al, 2015). A recent study applied BISICLES in a palaeo setting, focussing on simulating part of the British and Irish ice sheet, and highlighted the importance of marine interactions and marine ice sheet instability during the last deglaciation of the British Isles (Gandy et al, 2018). https://doi.org/10.5194/gmd-2019-304 Preprint.…”

Section: Introductionmentioning

confidence: 99%

Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)

Matero¹,

Gregoire²,

Ivanovic³

2019

Preprint

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Abstract. Simulating the demise of the Laurentide Ice Sheet covering the Hudson Bay in the early Holocene (10-7 ka) is important for understanding the role of accelerated changes in ice sheet topography and melt in the 8.2 ka event, a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical ice loss and marine interactions could have significantly accelerated the ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past ice sheets. Here, we developed an ice sheet model setup for studying the Laurentide Ice Sheet’s Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES ice sheet model, an efficient marine ice sheet model of the latest generation, capable of refinement to kilometre-scale resolution and higher-order ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the ice sheet temperature, recent ice sheet reconstructions for developing the topography of the region and ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the ice sheet and the associated meltwater pulse has realistic timing. Furthermore,the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representation of the glacial dynamics and marine interactions are key for correctly simulating the pattern of early Holocene ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.

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Marine ice sheet instability and ice shelf buttressing of the Minch Ice Stream, northwest Scotland

Cited by 28 publications

References 70 publications

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)

Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)

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