Tides and the flow of Rutford Ice Stream, West Antarctica

Gudmundsson, G. Hilmar

doi:10.1029/2006jf000731

Cited by 123 publications

(256 citation statements)

References 44 publications

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“…In contrast, the surface tilt between the two sites matches closely the ice shelf displacement in both the relative amplitude and phase, suggesting that tidal tilt rather than tidal currents is the primary driver of the horizontal movements and the strain between sites (Figure 3). Since ice at À20 C is expected to be almost purely elastic at diurnal and semidiurnal periods [Gudmundsson, 2007], the cold ice of RIS behaves predominantly as an elastic sheet at tidal time scales. Anchored at its southern grounding lines, the ice shelf responds to twice daily changes in tilt, causing large variations in both velocity and strain, as well as amplifying the horizontal motions towards the ice front.…”

Section: Resultsmentioning

confidence: 99%

Diurnal and semidiurnal tide‐induced lateral movement of Ronne Ice Shelf, Antarctica

Makinson

King

Nicholls

et al. 2012

Geophysical Research Letters

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[1] Recent GPS observations from a spatially extensive network across Ronne Ice Shelf show significant daily ice flow variations. At all sites, the almost-synchronous horizontal displacements occur at diurnal and semidiurnal tidal periods. During spring tides, displacements, velocities and strains near the ice front have superimposed oscillations that are AE300% of their mean values and occur over a six-hour period, resulting in regular ice shelf flow reversals. Close to ice stream grounding lines, however, the horizontal diurnal and semidiurnal signals decay and almost vanish. From our analysis, we conclude that ice shelves respond primarily elastically to tidal tilting, thus accounting for the observed diurnal and semidiurnal flow variations, and their amplification toward the ice shelf front. Our findings suggest that detailed modeling of these data could provide improved ice shelf and ice stream models for correctly simulating ice shelf flow and predicting future ice sheet evolution.

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Section: Resultsmentioning

confidence: 99%

Diurnal and semidiurnal tide‐induced lateral movement of Ronne Ice Shelf, Antarctica

Makinson

King

Nicholls

et al. 2012

Geophysical Research Letters

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“…Thus, over forcings with periods <4 days and stresses of less than �100 kPa, purely elastic models should be a reasonable approximation. In particular, tidal forcings (period 1 day) over ice plains or ice streams (stresses 30 kPa) should be well approximated by elastic models (Gudmundsson, 2007).…”

Section: Governing Equationsmentioning

confidence: 99%

An improved model for tidally modulated grounding-line migration

Tsai

Gudmundsson

2015

J. Glaciol.

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ABSTRACT. Understanding grounding-line dynamics is necessary for predictions of long-term ice-sheet stability. However, despite growing observations of the tidal influence on grounding-line migration, this short-timescale migration is poorly understood, with most modeling attempts assuming beam theory to calculate displacements. Here we present an improved model of tidal grounding-line migration that treats migration as an elastic fracture problem, forced by the additional ocean water pressure from the tide. This new model predicts that the grounding line cannot be assumed to be in hydrostatic equilibrium and, furthermore, that migration is inherently asymmetric and nonlinear, with migration distances that are not proportional to the tidal load. Specifically, for constant surface slope, the grounding line migrates upstream approximately ten times further as the tide rises from mean sea level to high tide than it migrates downstream as the tide falls from mean sea level to low tide, and migration distances are substantially larger than simple flotation arguments suggest. Numerical tests also show that the dependence of migration distance on elastic moduli and ice-sheet thickness are inconsistent with predictions of beam theory for a range of realistic values. Finally, applying the new model to observations in Antarctica results in new estimates of bed slopes, though these estimates remain uncertain due to imperfect knowledge of the relevant rheological parameters.

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“…High temporal resolution GPS monitoring of ice motion at RIS site C1, 10 km upstream of the grounding line, has shown that horizontal ice velocity varies by ∼ 20 % on fortnightly timescales in response to tidally modulated vertical displacement of the FilchnerRonne Ice Shelf (Gudmundsson, 2006(Gudmundsson, , 2007Murray et al, 2007;Minchew et al, 2017). In addition, passive seismic monitoring has demonstrated increased seismic activity during tidal cycles (Aðalgeirsdóttir et al, 2008).…”

Section: Are Ice-stream Beds Dynamic?mentioning

confidence: 99%

How dynamic are ice-stream beds?

et al. 2018

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Abstract. Projections of sea-level rise contributions from West Antarctica's dynamically thinning ice streams contain high uncertainty because some of the key processes involved are extremely challenging to observe. An especially poorly observed parameter is sub-decadal stability of ice-stream beds, which may be important for subglacial traction, till continuity and landform development. Only two previous studies have made repeated geophysical measurements of ice-stream beds at the same locations in different years, but both studies were limited in spatial extent. Here, we present the results from repeat radar measurements of the bed of Pine Island Glacier, West Antarctica, conducted 3-6 years apart, along a cumulative ∼ 60 km of profiles. Analysis of the correlation of bed picks between repeat surveys shows that 90 % of the bed displays no significant change despite the glacier increasing in speed by up to 40 % over the last decade. We attribute the negligible detection of morphological change at the bed of Pine Island Glacier to the ubiquitous presence of a deforming till layer, wherein sediment transport is in steady state, such that sediment is transported along the basal interface without inducing morphological change to the radarsounded basal interface. Given the precision of our measurements, the upper limit of subglacial erosion observed here is 500 mm a −1 , far exceeding erosion rates reported for glacial settings from proglacial sediment yields, but substantially below subglacial erosion rates of 1.0 m a −1 previously reported from repeat geophysical surveys in West Antarctica.

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Tides and the flow of Rutford Ice Stream, West Antarctica

Cited by 123 publications

References 44 publications

Diurnal and semidiurnal tide‐induced lateral movement of Ronne Ice Shelf, Antarctica

Diurnal and semidiurnal tide‐induced lateral movement of Ronne Ice Shelf, Antarctica

An improved model for tidally modulated grounding-line migration

How dynamic are ice-stream beds?

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