Exploring the ingredients required to successfully model the placement, generation, and evolution of ice streams in the British-Irish Ice Sheet

Gandy, Niall; Gregoire, Lauren; Ely, Jeremy C.; Cornford, Stephen; Clark, Christopher D.; Hodgson, David M.

doi:10.1016/j.quascirev.2019.105915

Cited by 28 publications

(49 citation statements)

References 131 publications

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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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“…This means BISICLES can simulate grounding line migration without parameterization, unlike models previously used to simulate the deglaciation of the North Sea (Patton et al, 2017). BISICLES has previously been successfully used to simulate the evolution of contemporary (Cornford et al, 2016;Favier et al, 2014;Gong et al, 2017) and palaeo (Gandy et al, 2018(Gandy et al, , 2019 ice sheets. We set-up BISICLES in a manner similar to Gandy et al (2019), in that an idealized basal hydrology scheme is coupled to a Coulomb sliding law dependent on ice and basal water pressure, in order to simulate regions of ice streaming.…”

Section: Methodsmentioning

confidence: 99%

Collapse of the Last Eurasian Ice Sheet in the North Sea Modulated by Combined Processes of Ice Flow, Surface Melt, and Marine Ice Sheet Instabilities

et al. 2021

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The North Sea sector is a shallow marine basin, which is topographically dominated by the Norwegian Channel, a deep (∼200-600 m) trough on the southwestern Norwegian coast (Figure 1). The North Sea sector hosts an archive of palaeo ice sheet dynamics with marine, lacustrine, and terrestrial margins. Therefore, this sector has the potential to provide an analog for contemporary ice sheets and to inform long-term behavior of ice sheets with different marginal settings. For example, the northern marine margin may have been vulnerable to similar marine processes that are in effect in contemporary West Antarctica (Favier et al., 2014;Joughin et al., 2014;Shepherd et al., 2001). These marine sectors are prone to instabilities of retreat, which represent the largest source of uncertainty for future sea level projections (Edwards et al., 2019). Therefore, understanding the deglaciation of marine ice sheet sectors is a key challenge of glaciology. Ice sheet evolution over the North Sea basin is also important in understanding the Relative Sea Level (RSL) change of the basin since the last deglaciation (Bradley et al., 2011). Furthermore, the history of glaciation is a key cause of the complicated stratigraphic record that needs to be understood to plan economically viable offshore wind farm developments in the North Sea (e.g., Emery et al., 2019). All considered, the requirement to better understand the deglaciation of the North Sea sector of the Eurasian Ice Sheet complex has motivated several previous empirical and modeling studies (e.g.

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“…Similarly, more recent modelling experiments by Gandy et al . (2019) simulate a fast‐flowing (300–1000 m a −1 ) MnIS reaching the outer continental shelf in < 2500 years.…”

Section: Chronological Synthesis Interpretation and Palaeoglaciological Reconstructionmentioning

confidence: 99%

“…These studies have focused on: the landform evidence of ice streaming onshore (Bradwell et al ., 2007, 2008a: Hughes et al ., 2014); the submarine sediment and landform record (Bradwell et al ., 2008a; Stoker et al ., 2009; Bradwell and Stoker, 2015a, 2016); the evidence for thermal zonation and tributary flow (Ballantyne, 2010; Fabel et al ., 2012; Bradwell, 2013); and most recently the submarine geological record and chronology of grounding‐line retreat (Bradwell et al ., 2019). In addition to this, numerical modelling has shown the MnIS to be a dynamic yet quasi‐stable feature that dominated flow geometry in the ice sheet's NW sector (Boulton and Hagdorn, 2006; Hubbard et al ., 2009; Gandy et al ., 2019). Higher order modelling work, focusing on the MnIS catchment, has highlighted the importance of subglacial bed slope, trough width and ice‐shelf buttressing in controlling the retreat rate and overall stability of the ice stream (Gandy et al ., 2018) – a finding also emphasized in recent empirical work (Bradwell et al ., 2019).…”

Section: Introductionmentioning

confidence: 99%

Pattern, style and timing of British–Irish Ice Sheet advance and retreat over the last 45 000 years: evidence from NW Scotland and the adjacent continental shelf

Bradwell

Fabel

Clark

et al. 2021

J Quaternary Science

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Predicting the future response of ice sheets to climate warming and rising global sea level is important but difficult. This is especially so when fast‐flowing glaciers or ice streams, buffered by ice shelves, are grounded on beds below sea level. What happens when these ice shelves are removed? And how do the ice stream and the surrounding ice sheet respond to the abruptly altered boundary conditions? To address these questions and others we present new geological, geomorphological, geophysical and geochronological data from the ice‐stream‐dominated NW sector of the last British–Irish Ice Sheet (BIIS). The study area covers around 45 000 km2 of NW Scotland and the surrounding continental shelf. Alongside seabed geomorphological mapping and Quaternary sediment analysis, we use a suite of over 100 new absolute ages (including cosmogenic‐nuclide exposure ages, optically stimulated luminescence ages and radiocarbon dates) collected from onshore and offshore, to build a sector‐wide ice‐sheet reconstruction combining all available evidence with Bayesian chronosequence modelling. Using this information we present a detailed assessment of ice‐sheet advance/retreat history, and the glaciological connections between different areas of the NW BIIS sector, at different times during the last glacial cycle. The results show a highly dynamic, partly marine, partly terrestrial, ice‐sheet sector undergoing large size variations in response to sub‐millennial‐scale climatic (Dansgaard–Oeschger) cycles over the last 45 000 years. Superimposed on these trends we identify internally driven instabilities, operating at higher frequency, conditioned by local topographic factors, tidewater dynamics and glaciological feedbacks during deglaciation. Specifically, our new evidence indicates extensive marine‐terminating ice‐sheet glaciation of the NW BIIS sector during Greenland Stadials 12 to 9 – prior to the main ‘Late Weichselian’ ice‐sheet glaciation. After a period of restricted glaciation, in Greenland Interstadials 8 to 6, we find good evidence for rapid renewed ice‐sheet build‐up in NW Scotland, with the Minch ice‐stream terminus reaching the continental shelf edge in Greenland Stadial 5, perhaps only briefly. Deglaciation of the NW sector took place in numerous stages. Several grounding‐zone wedges and moraines on the mid‐ and inner continental shelf attest to significant stabilizations of the ice‐sheet grounding line, or ice margin, during overall retreat in Greenland Stadials 3 and 2, and to the development of ice shelves. NW Lewis was the first substantial present‐day land area to deglaciate, in the first half of Greenland Stadial 3 at a time of globally reduced sea‐level c. 26 kabp, followed by Cape Wrath at c. 24 kabp. The topographic confinement of the Minch straits probably promoted ice‐shelf development in early Greenland Stadial 2, providing the ice stream with additional support and buffering it somewhat from external drivers. However, c. 20–19 kabp, as the grounding‐line migrated into shoreward deepening water, co...

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Exploring the ingredients required to successfully model the placement, generation, and evolution of ice streams in the British-Irish Ice Sheet

Cited by 28 publications

References 131 publications

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Proglacial Lakes Control Glacier Geometry and Behavior During Recession

Collapse of the Last Eurasian Ice Sheet in the North Sea Modulated by Combined Processes of Ice Flow, Surface Melt, and Marine Ice Sheet Instabilities

Pattern, style and timing of British–Irish Ice Sheet advance and retreat over the last 45 000 years: evidence from NW Scotland and the adjacent continental shelf

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