Past ice flow in Wahlenbergfjorden and its implications for late Quaternary ice sheet dynamics in northeastern Svalbard

Abstract. Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law and to the treatment of stresses and melt rates near the grounding line. We study the effects of these numerical choices on marine ice sheet dynamics in the Community Ice Sheet Model (CISM). In the framework of the Marine Ice Sheet Model Intercomparison Project 3d (MISMIP3d), we show that a depth-integrated, higher-order solver gives results similar to a 3D (Blatter–Pattyn) solver. We confirm that using a grounding line parameterization to approximate stresses in the grounding zone leads to accurate representation of ice sheet flow with a resolution of ∼2 km, as opposed to ∼0.5 km without the parameterization. In the MISMIP+ experimental framework, we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice sheet geometry, forcing, or model numerics. In both experimental frameworks, ice flow is sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate and ∼1 km (arguably 2 km) when the connectivity is strong.

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Marine ice-sheet experiments with the Community Ice Sheet Model using the MISMIP+ experimental framework.

10.5194/egusphere-egu21-6608 ◽

2021 ◽

Author(s):

Gunter Leguy ◽

William Lipscomb ◽

Xylar Asay-Davis

Keyword(s):

Ice Sheet ◽

Ice Flow ◽

Friction Law ◽

Friction Laws ◽

Basal Friction ◽

Grounding Line ◽

Hydrological System ◽

Flow Approximation ◽

Intercomparison Project ◽

Ice Sheet Dynamics

Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law, and to the treatment of stresses and melt rates near the grounding line. We present the effects of these numerical choices on marine ice-sheet dynamics in the Community Ice Sheet Model (CISM). In the experimental framework of the Marine Ice Sheet Model Intercomparison Project (MISMIP+), we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice-sheet geometry, forcing, or model numerics. In the MISMIP+ framework, the ice flow is also sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of &#8764;2 km (arguably 4 km) when the connectivity is low or moderate, and &#8764;1 km (arguably 2 km) when the connectivity is strong.

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ESD Ideas: Propagation of high-frequency forcing to ice age dynamics

Earth System Dynamics ◽

10.5194/esd-10-257-2019 ◽

2019 ◽

Vol 10 (2) ◽

pp. 257-260 ◽

Cited By ~ 3

Author(s):

Mikhail Y. Verbitsky ◽

Michel Crucifix ◽

Dmitry M. Volobuev

Keyword(s):

Conservation Laws ◽

High Frequency ◽

Ice Sheet ◽

Ice Age ◽

Ice Flow ◽

Age Dynamics ◽

Nonlinear Character ◽

Continuous Background ◽

Ice Sheet Dynamics ◽

Flow Conservation

Abstract. Palaeoclimate records display a continuous background of variability connecting centennial to 100 kyr periods. Hence, the dynamics at the centennial, millennial, and astronomical timescales should not be treated separately. Here, we show that the nonlinear character of ice sheet dynamics, which was derived naturally from the ice-flow conservation laws, provides the scaling constraints to explain the structure of the observed spectrum of variability.

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Monsoonal Forcing of European Ice‐Sheet Dynamics During the Late Quaternary

Geophysical Research Letters ◽

10.1029/2018gl078751 ◽

2018 ◽

Vol 45 (14) ◽

pp. 7066-7074 ◽

Cited By ~ 1

Author(s):

Stefanie Kaboth‐Bahr ◽

André Bahr ◽

Christian Zeeden ◽

Samuel Toucanne ◽

Frédérique Eynaud ◽

...

Keyword(s):

Late Quaternary ◽

Ice Sheet ◽

Ice Sheet Dynamics

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Multi-proxy analysis of Late Quaternary ODYSSEA Contourite Depositional System (Ross Sea, Antarctica) and the depositional record of contour current and cold, dense waters

10.5194/egusphere-egu2020-12940 ◽

2020 ◽

Author(s):

Michele Rebesco ◽

Renata Giulia Lucchi ◽

Andrea Caburlotto ◽

Stefano Miserocchi ◽

Leonardo Langone ◽

...

Keyword(s):

Ross Sea ◽

Late Quaternary ◽

Ice Sheet ◽

Current Strength ◽

Global Ocean ◽

General Assembly ◽

Geophysical Research ◽

Dense Water ◽

Depositional System ◽

Ice Sheet Dynamics

The Ross Ice Shelf is the Antarctic region that over the last deglaciation experienced the greatest change in areal ice cover. Today, cold, dense and saline water masses (brines) produced in the Ross Sea polynya, flow from the shelf to the deep ocean providing a significant contribution to the propelling of the global ocean circulation regulating the climate. In particular, the Hillary Canyon in the Eastern Ross Sea is the main conduit through which brines descend the slope to reach the deeper ocean and is thus one of the greatest regions of cold, dense water export in the world.A Contourite Depositional System (the ODYSSEA CDS) on the western flank of the Hillary Canyon is inferred to have been generated through several hundred-thousand years by along-slope, contour currents that transported and accumulated the sediments brought down the Hillary Canyon by means of brines. A multi-proxy investigation was conducted on the shallowest part of the ODYSSEA CDS depositional sequences, which we expect to contain i) the record of the brine formation, ii) the indication on contour current strength through time, and iii) their interplay and modulation associated to climate change.Six gravity cores, collected in both the proximal and distal area of the ODYSSEA CDS, were studied through multi-proxy analyses including sediment physical properties (texture, structures, water content, wet bulk density), compositional characteristics (XRF, geochemistry and detrital apatite, zircon, and rutile U-Pb on ice-rafted debris) (Lucchi et al., 2019; Neofitu et al., 2020) and microfossil content (planktonic and benthic foraminifera, calcareous nannofossils and diatoms). An age model has been reconstructed combining palaeomagnetic record, biostratigraphic content, tephrochronology and AMS radiocarbon dating on planktonic foraminifera tests.Inferred variations in dense water formation, contour current strength and ice sheet dynamics are discussed in the light of our data interpretation.&#160;Lucchi, R.G., Caburlotto, A., Miserocchi, S., Liu, Y., Morigi, C., Persico, D., Villa, G., Langone, L., Colizza, E., Macr&#236;, P., Sagnotti, L., Conte, R., Rebesco, M., 2019. The depositional record of the Odyssea drift (Ross Sea, Antarctica). Geophysical Research Abstracts, Vol. 21, EGU2019-10409-1, 2019. EGU General Assembly, Vienna (Austria), 7&#8211;12, April, 2019 (POSTER).Neofitu, R., Mark, C., Rebesco, M., Lucchi, R.G., Douss, N., Morigi, C., Kelley, S., Daly, J.S., 2020. Tracking Late Quaternary ice sheet dynamics by multi-proxy detrital mineral U-Pb analysis: A case study from the Odyssea contourite, Ross Sea, Antarctica. Geophysical Research Abstracts. EGU General Assembly, Vienna (Austria), 3&#8211;8, May, 2020 (POSTER for session CL1.11).

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Surface exposure dating of the Pierre Sublobe of the James Lobe, Laurentide Ice Sheet

Quaternary Research ◽

10.1017/qua.2020.16 ◽

2020 ◽

Vol 97 ◽

pp. 88-98

Author(s):

Stephanie L. Heath ◽

Thomas V. Lowell ◽

Brenda L. Hall

Keyword(s):

Late Quaternary ◽

Ice Sheet ◽

Age Dating ◽

Laurentide Ice Sheet ◽

Des Moines Lobe ◽

Exposure Dating ◽

Des Moines ◽

Contrast Exposure ◽

Ice Sheet Dynamics ◽

Exposure Ages

AbstractThe Laurentide Ice Sheet of the last glacial period terminated in several lobes along its southern margin. The timing of maximum extent may have varied among the terminal lobes owing to internal ice sheet dynamics and spatially variable external controls. Some terminal ice lobes, such as the westernmost James Lobe, remain poorly dated. To determine the timing of maximum ice extent in this key location, we have mapped glacial deposits left by the Pierre Sublobe in South Dakota and applied 10Be surface exposure age dating on boulders on moraine ridges associated with three distinct late Quaternary glacial drifts. The oldest and most extensive “Tazewell” drift produced variable 10Be surface exposure ages spanning 20–7 ka; the large range is likely attributable to moraine degradation and subsequent boulder exhumation. The oldest ages of about 20 ka are probably limiting minimum ages for the Tazewell moraine surfaces. By contrast, exposure ages of the youngest “Mankato” drift of the easternmost Pierre Sublobe tightly cluster at about 16 ka. This age for the Pierre Sublobe is consistent with the nearby Des Moines Lobe, suggesting both acted together.

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The late Quaternary stratigraphic record northwest of Montréal: regional ice-sheet dynamics, ice-stream activity, and early deglacial events

Canadian Journal of Earth Sciences ◽

10.1139/e05-118 ◽

2006 ◽

Vol 43 (4) ◽

pp. 461-485 ◽

Cited By ~ 19

Author(s):

Martin Ross ◽

Michel Parent ◽

Beatriz Benjumea ◽

James Hunter

Keyword(s):

Late Quaternary ◽

Late Glacial ◽

Ice Flow ◽

Glacial Sediments ◽

Ice Stream ◽

Digital Elevation ◽

Flow Features ◽

Ice Sheet Dynamics ◽

Late Wisconsinan ◽

Elevation Model

The Quaternary sediments of previously unstudied buried valleys and sections near Montréal are analyzed and other sites are revisited to further develop the stratigraphic framework of the St. Lawrence Lowland and to establish regional glacial and deglacial models. The southwest-trending buried valleys were investigated by stratigraphic drilling and high-resolution seismic profiling. The Quaternary succession consists, from base to top, of proximal glaciolacustrine sediments, two superposed till sheets (Argenteuil and Oka tills) of inferred Late Wisconsinan age, and Champlain Sea sediments. The glacial sediments of this sequence record an ice advance toward south (Argenteuil Till) followed by an abrupt ice-flow shift toward the southwest (Oka Till). Compositional and geomorphic data indicate that Oka Till is ubiquitous and is associated with a regional set of glacial landforms. The analysis of a regional digital elevation model in combination with published ice-flow indicators shows convergent flow patterns from the OttawaMontréalAdirondack regions toward the Lake Ontario basin. Landforms produced by the inferred ice stream are locally crosscut by southward-trending ice-flow features. Hence southward flow in the upper St. Lawrence Valley seemingly took place in two distinct contexts: (1) during full glacial conditions, as ice margins stood at or near the late glacial maximum limits, and (2) during late deglaciation, as a post-ice stream reequilibration mechanism. Early deglacial events in the study area were also characterized by subglacial meltwater channelling and erosion along the valleys, subaquatic outwash deposition in glacial Lake Candona, and rapid infill of the valleys during the early stages of the ensuing Champlain Sea.

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Late Quaternary climate variability as recorded by micropalaeontological diatom data and geochemical data in the western Ross Sea, Antarctica

Antarctic Science ◽

10.1017/s0954102013000199 ◽

2013 ◽

Vol 25 (6) ◽

pp. 804-820 ◽

Cited By ~ 4

Author(s):

R. Tolotti ◽

C. Salvi ◽

G. Salvi ◽

M.C. Bonci

Keyword(s):

Continental Slope ◽

Ross Sea ◽

Late Quaternary ◽

Ice Sheet ◽

Geochemical Data ◽

Flow Paths ◽

Ice Flow ◽

Quaternary Climate ◽

History Of ◽

Geochemical Analyses

AbstractCores acquired from the Ross Sea continental shelf and continental slope during the XXX Italian Programma Nazionale di Ricerche in Antartide (PNRA) were analysed and yielded interesting micropalaeontological, biostratigraphic diatom results and palaeoceanographic implications. These multi-proxy analyses enabled us to reconstruct the glacial/deglacial history of this sector of the Ross embayment over the last 40 000 years, advancing our understanding of the Last Glacial Maximum (LGM) environmental and sedimentological processes linked to the Ross Sea ice sheet/ice shelf fluctuations in a basin and continental-slope environment, and allowed us to measure some of the palaeoceanographic dynamics. The central sector of the Ross Sea and part of its coast (south of the Drygalski Ice Tongue) enjoyed open marine conditions in the pre-LGM era (27 500–24 000 years bp). The retreat of the ice sheet could have been influenced by a southward shift of a branch of the Ross gyre, which triggered early deglaciation at c. 18 600 cal bp with a significant Modified Circumpolar Deep Water inflow over the continental slope at c. 14 380 cal BP. We assume that a lack of depositional material in each core, although at different times, represents a hiatus. Other than problems in core collection, this could be due to the onset of modern oceanographic conditions, with strong gravity currents and strong High Salinity Shelf Water exportation. Moreover, we presume that improvements in biostratigraphy, study of reworked diatom taxa, and lithological and geochemical analyses will provide important constraints for the reconstruction of the LGM grounding line, ice-flow lines and ice-flow paths and an interesting tool for reconstructing palaeo-sub-bottom currents in this sector of the Ross embayment.

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PISM-LakeCC: Implementing an adaptive proglacial lake boundary into an ice sheet model

10.5194/tc-2020-353 ◽

2020 ◽

Author(s):

Sebastian Hinck ◽

Evan J. Gowan ◽

Xu Zhang ◽

Gerrit Lohmann

Keyword(s):

Boundary Conditions ◽

Ice Sheet ◽

Laurentide Ice Sheet ◽

Hudson Bay ◽

Ice Streams ◽

Ice Flow ◽

Glacial Retreat ◽

Proglacial Lakes ◽

Lake Model ◽

Ice Sheet Dynamics

Abstract. Geological records show that vast proglacial lakes existed along the land terminating margins of palaeo ice sheets in Europe and North America. Proglacial lakes impact ice sheet dynamics by imposing marine-like boundary conditions at the ice margin. These lacustrine boundary conditions include changes in the ice sheet’s geometry, stress balance and frontal ablation and therefore affect the entire ice sheet’s mass balance. This interaction, however, has not been rigorously implemented in ice sheet models. In this study, the implementation of an adaptive lake boundary into the Parallel Ice Sheet Model (PISM) is described and applied to the glacial retreat of the Laurentide Ice Sheet (LIS). The results show that the presence of proglacial lakes locally enhances the ice flow. Along the continental ice margin, ice streams and ice lobes can be observed. Lacustrine terminating ice streams cause immense thinning of the ice sheet’s interior and thus play a significant role in the demise of the LIS. Due to the presence of lakes, a process similar to the marine ice sheet instability causes the collapse of the ice saddle over Hudson Bay, which blocked drainage via the Hudson Strait. In control experiments without a lake model, Hudson Bay is still glaciated at the end of the simulation. Future studies should target the development of parametrizations that better describe the glacial-lacustrine interactions.

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