scholarly journals A thermomechanical model of ice-shelf flow

1996 ◽  
Vol 23 ◽  
pp. 13-20 ◽  
Author(s):  
Vincent Rommelaere ◽  
Catherine Ritz
Keyword(s):  
Small Island ◽  
Numerical Techniques ◽  
Ice Shelf ◽  
Thermomechanical Model ◽  
Grounding Line ◽  
Shelf Flow

An ice-shelf model which features efficient numerical techniques is developed to determine the back-force exerted by sides and pinning points, such as islands of an embayed ice shelf. The model is applied to three ideal geometries and shows that the restraint exerted by a small island, even far downstream from the grounding line, can represent about one-half of the total restraint due to the embayment. Our results are further interpreted to suggest several criteria useful for testing any ice-shelf model.

scholarly journals A thermomechanical model of ice-shelf flow

1996 ◽  
Vol 23 ◽  
pp. 13-20 ◽  
Author(s):  
Vincent Rommelaere ◽  
Catherine Ritz
Keyword(s):  
Small Island ◽  
Numerical Techniques ◽  
Ice Shelf ◽  
Thermomechanical Model ◽  
Grounding Line ◽  
Shelf Flow

An ice-shelf model which features efficient numerical techniques is developed to determine the back-force exerted by sides and pinning points, such as islands of an embayed ice shelf. The model is applied to three ideal geometries and shows that the restraint exerted by a small island, even far downstream from the grounding line, can represent about one-half of the total restraint due to the embayment. Our results are further interpreted to suggest several criteria useful for testing any ice-shelf model.

scholarly journals Fracture and back stress along the Byrd Glacier flowband on the Ross Ice Shelf

2004 ◽  
Vol 16 (3) ◽  
pp. 345-354 ◽  
Author(s):  
JAMES P. KENNEALLY ◽  
TERENCE J. HUGHES
Keyword(s):  
Fracture Mechanics ◽  
Ductile Fracture ◽  
Back Stress ◽  
Ice Thickness ◽  
Subsequent Growth ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Transverse Tensile ◽  
Grounding Line ◽  
Shelf Flow

East Antarctic ice discharged by Byrd Glacier continues as a flowband to the calving front of the Ross Ice Shelf. Flow across the grounding line changes from compressive to extensive as it leaves the fjord through the Transantarctic Mountains occupied by Byrd Glacier. Magnitudes of the longitudinal compressive stress that suppress opening of transverse tensile cracks are calculated for the flowband. As compressive back stresses diminish, initial depths and subsequent growth of these cracks, and their spacing, are calculated using theories of elastic and ductile fracture mechanics. Cracks are initially about one millimeter wide, with approximately 30 m depths and 20 m spacings for a back stress of 83 kPa at a distance of 50 km beyond the fjord, where floating ice is 600 m thick. When these crevasses penetrate the whole ice thickness, they release tabular icebergs 20 km to 100 km wide, spaced parallel to the calving front of the Ross Ice Shelf.

scholarly journals Bathymetric controls on calving processes at Pine Island Glacier

2018 ◽  
Vol 12 (6) ◽  
pp. 2039-2050 ◽  
Author(s):  
Jan Erik Arndt ◽  
Robert D. Larter ◽  
Peter Friedl ◽  
Karsten Gohl ◽  
Kathrin Höppner ◽  
...  
Keyword(s):  
Sea Level ◽  
Satellite Imagery ◽  
Back Stress ◽  
Ice Shelf ◽  
The North ◽  
Grounding Line ◽  
Intermittent Contact ◽  
Shelf Flow ◽  
Line Positions ◽  
Observational Record

Abstract. Pine Island Glacier is the largest current Antarctic contributor to sea-level rise. Its ice loss has substantially increased over the last 25 years through thinning, acceleration and grounding line retreat. However, the calving line positions of the stabilising ice shelf did not show any trend within the observational record (last 70 years) until calving in 2015 led to unprecedented retreat and changed the alignment of the calving front. Bathymetric surveying revealed a ridge below the former ice shelf and two shallower highs to the north. Satellite imagery shows that ice contact on the ridge was likely lost in 2006 but was followed by intermittent contact resulting in back stress fluctuations on the ice shelf. Continuing ice-shelf flow also led to occasional ice-shelf contact with the northern bathymetric highs, which initiated rift formation that led to calving. The observations show that bathymetry is an important factor in initiating calving events.

scholarly journals Insights into ice stream dynamics through modeling their response to tidal forcing

2014 ◽  
Vol 8 (1) ◽  
pp. 659-689 ◽  
Author(s):  
S. H. R. Rosier ◽  
G. H. Gudmundsson ◽  
J. A. M. Green
Keyword(s):  
Flow Line ◽  
Coupling Length ◽  
Length Scale ◽  
Ice Shelf ◽  
Ice Streams ◽  
Tidal Forcing ◽  
Ice Stream ◽  
Grounding Line ◽  
Basal Sliding ◽  
Shelf Flow

Abstract. The tidal forcing of ice streams at their ocean boundary can serve as a natural experiment to gain an insight into their dynamics and constrain the basal sliding law. A 3-D visco-elastic full Stokes model of coupled ice-stream ice-shelf flow is used to investigate the response of ice streams to ocean tides. In agreement with previous results based on flow-line modeling and with a fixed grounding line position, we find that a non-linear basal sliding law can reproduce long period modulation of tidal forcing found in field observations, and the inclusions of lateral effects and grounding line migration do not alter this result. Further analysis of modeled ice stream flow shows a varying stress-coupling length scale of boundary effects upstream of the grounding line. We derive a visco-elastic stress coupling length scale from ice stream equations that depends on the forcing period and closely agrees with model output.

scholarly journals Bathymetric Controls on Calving Processes at Pine Island Glacier

2018 ◽  
Author(s):  
Jan Erik Arndt ◽  
Robert D. Larter ◽  
Peter Friedl ◽  
Karsten Gohl ◽  
Kathrin Höppner
Keyword(s):  
Sea Level ◽  
Satellite Imagery ◽  
Back Stress ◽  
Ice Shelf ◽  
The North ◽  
Grounding Line ◽  
Intermittent Contact ◽  
Shelf Flow ◽  
Line Positions ◽  
Observational Record

Abstract. Pine Island Glacier is the largest current Antarctic contributor to sea level rise. Its ice loss has substantially increased over the last 25 years through thinning, acceleration and grounding line retreat. However, the calving line positions of the stabilizing ice shelf did not show any trend within the observational record (last 70 years) until calving in 2015 led to unprecedented retreat and changed alignment of the calving front. Bathymetric surveying revealed a ridge below the former ice shelf and two shallower highs to the north. Satellite imagery shows that ice contact on the ridge likely was lost in 2006 but was followed by intermittent contact resulting in back stress fluctuations on the ice shelf. Continuing ice shelf flow also led to occasional ice shelf contact with the northern bathymetric highs, which initiated rift formation that led to calving. The observations show that bathymetry is an important factor in initiating calving events.

scholarly journals Insights into ice stream dynamics through modelling their response to tidal forcing

2014 ◽  
Vol 8 (5) ◽  
pp. 1763-1775 ◽  
Author(s):  
S. H. R. Rosier ◽  
G. H. Gudmundsson ◽  
J. A. M. Green
Keyword(s):  
Flow Line ◽  
Coupling Length ◽  
Length Scale ◽  
Ice Shelf ◽  
Ice Streams ◽  
Tidal Forcing ◽  
Ice Stream ◽  
Grounding Line ◽  
Basal Sliding ◽  
Shelf Flow

Abstract. The tidal forcing of ice streams at their ocean boundary can serve as a natural experiment to gain an insight into their dynamics and constrain the basal sliding law. A nonlinear 3-D viscoelastic full Stokes model of coupled ice stream ice shelf flow is used to investigate the response of ice streams to ocean tides. In agreement with previous results based on flow-line modelling and with a fixed grounding line position, we find that a nonlinear basal sliding law can qualitatively reproduce long-period modulation of tidal forcing found in field observations. In addition, we show that the inclusion of lateral drag, or allowing the grounding line to migrate over the tidal cycle, does not affect these conclusions. Further analysis of modelled ice stream flow shows a varying stress-coupling length scale of boundary effects upstream of the grounding line. We derive a viscoelastic stress-coupling length scale from ice stream equations that depends on the forcing period and closely agrees with model output.

scholarly journals Twenty-first century response of Petermann Glacier, northwest Greenland to ice shelf loss

2020 ◽  
pp. 1-11
Author(s):  
Emily A. Hill ◽  
G. Hilmar Gudmundsson ◽  
J. Rachel Carr ◽  
Chris R. Stokes ◽  
Helen M. King
Keyword(s):  
Sea Level ◽  
First Century ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Sea Levels ◽  
Grounding Line ◽  
Global Mean Sea Level ◽  
Near Future ◽  
Global Mean ◽  
Large Sections

Abstract Ice shelves restrain flow from the Greenland and Antarctic ice sheets. Climate-ocean warming could force thinning or collapse of floating ice shelves and subsequently accelerate flow, increase ice discharge and raise global mean sea levels. Petermann Glacier (PG), northwest Greenland, recently lost large sections of its ice shelf, but its response to total ice shelf loss in the future remains uncertain. Here, we use the ice flow model Úa to assess the sensitivity of PG to changes in ice shelf extent, and to estimate the resultant loss of grounded ice and contribution to sea level rise. Our results have shown that under several scenarios of ice shelf thinning and retreat, removal of the shelf will not contribute substantially to global mean sea level (<1 mm). We hypothesize that grounded ice loss was limited by the stabilization of the grounding line at a topographic high ~12 km inland of its current grounding line position. Further inland, the likelihood of a narrow fjord that slopes seawards suggests that PG is likely to remain insensitive to terminus changes in the near future.

scholarly journals Sensitivity of Pine Island Glacier, West Antarctica, to changes in ice-shelf and basal conditions: a model study

2002 ◽  
Vol 48 (163) ◽  
pp. 552-558 ◽  
Author(s):  
Marjorie Schmeltz ◽  
Eric Rignot ◽  
Todd K. Dupont ◽  
Douglas R. MacAyeal
Keyword(s):  
Shear Stress ◽  
Element Model ◽  
Shelf Area ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Stream ◽  
Model Study ◽  
Grounding Line ◽  
Glacier Velocity ◽  
Basal Shear

AbstractWe use a finite-element model of coupled ice-stream/ice-shelf flow to study the sensitivity of Pine Island Glacier, West Antarctica, to changes in ice-shelf and basal conditions. By tuning a softening coefficient of the ice along the glacier margins, and a basal friction coefficient controlling the distribution of basal shear stress underneath the ice stream, we are able to match model velocity to that observed with interferometric synthetic aperture radar (InSAR). We use the model to investigate the effect of small perturbations on ice flow. We find that a 5.5–13% reduction in our initial ice-shelf area increases the glacier velocity by 3.5–10% at the grounding line. The removal of the entire ice shelf increases the grounding-line velocity by > 70%. The changes in velocity associated with ice-shelf reduction are felt several tens of km inland. Alternatively, a 5% reduction in basal shear stress increases the glacier velocity by 13% at the grounding line. By contrast, softening of the glacier side margins would have to be increased a lot more to produce a comparable change in ice velocity. Hence, both the ice-shelf buttressing and the basal shear stress contribute significant resistance to the flow of Pine Island Glacier.

scholarly journals High basal melting forming a channel at the grounding line of Ross Ice Shelf, Antarctica

2016 ◽  
Vol 43 (1) ◽  
pp. 250-255 ◽  
Author(s):  
Oliver J. Marsh ◽  
Helen A. Fricker ◽  
Matthew R. Siegfried ◽  
Knut Christianson ◽  
Keith W. Nicholls ◽  
...  
Keyword(s):  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Grounding Line ◽  
Basal Melting

scholarly journals Dynamical processes involved in the retreat of marine ice sheets

2001 ◽  
Vol 47 (157) ◽  
pp. 271-282 ◽  
Author(s):  
Richard C.A. Hindmarsh ◽  
E. Le Meur
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line ◽  
Neutral Equilibrium ◽  
Generally True

AbstractMarine ice sheets with mechanics described by the shallow-ice approximation by definition do not couple mechanically with the shelf. Such ice sheets are known to have neutral equilibria. We consider the implications of this for their dynamics and in particular for mechanisms which promote marine ice-sheet retreat. The removal of ice-shelf buttressing leading to enhanced flow in grounded ice is discounted as a significant influence on mechanical grounds. Sea-level rise leading to reduced effective pressures under ice streams is shown to be a feasible mechanism for producing postglacial West Antarctic ice-sheet retreat but is inconsistent with borehole evidence. Warming thins the ice sheet by reducing the average viscosity but does not lead to grounding-line retreat. Internal oscillations either specified or generated via a MacAyeal–Payne thermal mechanism promote migration. This is a noise-induced drift phenomenon stemming from the neutral equilibrium property of marine ice sheets. This migration occurs at quite slow rates, but these are sufficiently large to have possibly played a role in the dynamics of the West Antarctic ice sheet after the glacial maximum. Numerical experiments suggest that it is generally true that while significant changes in thickness can be caused by spatially uniform changes, spatial variability coupled with dynamical variability is needed to cause margin movement.

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