Greenland Ice Sheet: Higher Nonlinearity of Ice Flow Significantly Reduces Estimated Basal Motion

Bons, Paul D.; Kleiner, Thomas; Llorens, Maria-Gema; Prior, David J.; Sachau, Till; Weikusat, Ilka; Jansen, Daniela

doi:10.1029/2018gl078356

Cited by 66 publications

(98 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ice rises archive their flow history in their characteristic internal stratigraphy (e.g. Conway et al, 1999;Nereson and Waddington, 2002;Drews et al, 2015), making them potentially suitable sites for ice-core drilling such as for the International Partnerships in Ice Core Sciences (IPICS) 2K and 40K Array (Brook et al, 2006). Due to very low deviatoric stresses near the bed of the divide region and the power law rheology of ice, the effective viscosity (e.g.…”

Section: Introductionmentioning

confidence: 99%

Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing

et al. 2019

View full text Add to dashboard Cite

Abstract. The majority of Antarctic ice shelves are bounded by grounded ice rises. These ice rises exhibit local flow fields that partially oppose the flow of the surrounding ice shelves. Formation of ice rises is accompanied by a characteristic upward-arching internal stratigraphy (“Raymond arches”), whose geometry can be analysed to infer information about past ice-sheet changes in areas where other archives such as rock outcrops are missing. Here we present an improved modelling framework to study ice-rise evolution using a satellite-velocity calibrated, isothermal, and isotropic 3-D full-Stokes model including grounding-line dynamics at the required mesh resolution (<500 m). This overcomes limitations of previous studies where ice-rise modelling has been restricted to 2-D and excluded the coupling between the ice shelf and ice rise. We apply the model to the Ekström Ice Shelf, Antarctica, containing two ice rises. Our simulations investigate the effect of surface mass balance and ocean perturbations onto ice-rise divide position and interpret possible resulting unique Raymond arch geometries. Our results show that changes in the surface mass balance result in immediate and sustained divide migration (>2.0 m yr−1) of up to 3.5 km. In contrast, instantaneous ice-shelf disintegration causes a short-lived and delayed (by 60–100 years) response of smaller magnitude (<0.75 m yr−1). The model tracks migration of a triple junction and synchronous ice-divide migration in both ice rises with similar magnitude but differing rates. The model is suitable for glacial/interglacial simulations on the catchment scale, providing the next step forward to unravel the ice-dynamic history stored in ice rises all around Antarctica.

show abstract

Section: Introductionmentioning

confidence: 99%

Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing

et al. 2019

View full text Add to dashboard Cite

show abstract

“…concerning melting and basal conditions. In particular, Bons et al (2018) thorough analysis of observational data of the Greenland Ice Sheet supports a flow exponent of n = 4, not the standard value of n = 3. This is in line with recent experiments which allow for large ice deformations in the lab, a regime similar to ice flow in glaciers, which also finds n > 3 (Qi et al, 2017).…”

Section: Discussionmentioning

confidence: 92%

“…Thorough analysis of the thickness, surface slope and velocities of the Greenland Ice Sheet, which are available through remote sensing, allow to relate the driving stress to the velocities and thus to infer the flow exponent n under realistic conditions. Bons et al (2018) find a flow exponent n = 4 in regions where sliding is negligible.…”

mentioning

confidence: 87%

Sensitivity of ice flow to uncertainty in flow law parameters in an idealized one-dimensional geometry

Zeitz¹,

Levermann²,

Winkelmann³

2020

Preprint

View full text Add to dashboard Cite

Abstract. The flow of ice drives mass losses in both, the Antarctic and the Greenland Ice Sheet. The projections of possible future sea-level rise rely on numerical ice-sheet models, which solve the physics of ice flow and melt. While a number of important uncertainties have been addressed by the ice-sheet modeling community, the flow law, which is at the center of most process-based ice-sheet models, has so far been assumed certain. Unfortunately, recent studies show that the parameters in the flow law might be uncertain and different from the widely accepted standard values. Here, we use an idealized flowline setup to investigate how uncertainties in the flow law translate into uncertainties in flow-driven mass loss given a step-wise increase of surface temperatures. We find that the measured range of flow parameters can double the flow-driven mass loss within the first centuries of warming, compared to a setting with standard parameters. The spread of ice loss due to an uncertainty in flow parameters is of the same order as the increase in mass loss due to increasing surface temperatures. While this study focuses on an idealized setting in order to disentangle the effect of the flow law from other effects, it is likely that this uncertainty carries over to realistic three-dimensional simulations of Greenland and Antarctica.

show abstract

“…CC BY 4.0 License. by many previous ice-rise divide studies, the commonly used exponent of the ice rheology law (n=3) is not able to reproduce the Raymond arch amplitudes from observations, but often a higher exponent (ni≈4.5) is chosen that better matches the arch amplitudes from observations (Martín et al, 2014;Drews et al, 2015;Bons et al, 2018). Moreover, Martín et al (2009a) showed that the commonly employed approximation of ice being an isotropic material in large-scale ice-sheet models is not valid at ice divides, where a preferential orientation of the ice crystals leads to enhanced ice deformation.…”

Section: Model Limitations 15mentioning

confidence: 99%

“…In this equation E is the enhancement factor, B is a viscosity parameter computed through an Arrhenius law, n is Glen's flow law parameter (n=3), and the effective strain rate is defined as˙ e 2 = tr(˙ 2 )/2. Although there is evidence that the Glen flow parameter is >3 (Bons et al, 2018), particularly near ice rises , we stick to the current modelling standard of n=3, because we focus on divide migration rather than Raymond arch amplitudes here. The same holds for the 20 enhancement factor, which is often used to account for anisotropic effects, but is set to 1 (isotropic conditions) in all simulations.…”

mentioning

confidence: 99%

Kinematic response of ice-rise divides to changes in oceanic and atmospheric forcing

Schannwell¹,

Drews²,

Ehlers³

et al. 2019

Preprint

View full text Add to dashboard Cite

Abstract. The majority of Antarctic ice shelves are bounded by grounded ice rises. These ice rises exhibit local flow regimes that partially oppose the flow of the surrounding ice shelves. Formation of such ice rises is accompanied by a characteristic upward arching internal stratigraphy (Raymond arches), archiving potential past divide migration and the onset of divide flow. Information about past ice-sheet conditions can therefore be retrieved in areas where other archives are missing. However, the quantitative interpretation of the stratigraphy requires modelling and radar observations. Hitherto, ice-rise modelling has been restricted to 2D and excluded the coupling between ice shelf and ice rise. This presents a major limitation for the interpretation of ice rises as ice-dynamic archive. Here we present an improved modelling framework to study ice-rise evolution using a calibrated, isothermal, and isotropic 3D Full-Stokes model including grounding-line dynamics at the required mesh resolution (<500 m). We apply the model to the Ekström Ice Shelf catchment containing two ice rises. Our results show that changes in the surface mass balance result in immediate and sustained divide migration (>2.0 m/yr) of up to 3.5 km. In contrast, instantaneous ice-shelf disintegration causes a short-lived and delayed (by 60–100 years) response of smaller magnitude (<0.75 m/yr). The model tracks migration of a triple junction and synchronous ice-divide migration in both ice rises with similar magnitude but differing rates. The model is suitable for glacial/interglacial simulations on the catchment scale, providing the next step forward to unravel the ice-dynamic history stored in ice rises all around Antarctica.

show abstract

Greenland Ice Sheet: Higher Nonlinearity of Ice Flow Significantly Reduces Estimated Basal Motion

Cited by 66 publications

References 50 publications

Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing

Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing

Sensitivity of ice flow to uncertainty in flow law parameters in an idealized one-dimensional geometry

Kinematic response of ice-rise divides to changes in oceanic and atmospheric forcing

Contact Info

Product

Resources

About