Ice-shelf Flow Research Articles

Oscillatory response of Larsen C Ice Shelf flow to the calving of iceberg A-68

Abstract The collapse of several ice shelves in the Antarctic Peninsula since the late 20th century has resulted in the upstream acceleration of multiple formerly buttressed outlet glaciers, raising questions about the stability of Antarctica's remaining ice shelves and the effects their demise may have upon inland ice. Here, we use high temporal resolution Sentinel-1A/B synthetic aperture radar-derived observations to assess the velocity response of Larsen C Ice Shelf (LCIS) to the calving of colossal iceberg A-68 in 2017. We find marked oscillations in ice-shelf flow across LCIS in the months following A-68's calving, beginning with a near-ice-shelf-wide slowdown of 11.3 m yr−1 on average. While falling close to the limits of detectability, these ice-flow variations appear to have been presaged by similar oscillations in the years prior to A-68's breakaway, associated primarily with major rifting events, together reflecting potentially hitherto unobserved ice-shelf mechanical processes with important implications for ice-shelf weakening. Such ice-flow oscillations were, however, short-lived, with more recent observations suggesting a deceleration below longer-term rates of ice flow. Collectively, our observations reveal complex spatial-temporal patterns of ice-flow variability at LCIS. Similarly abrupt fluctuations may have important implications for the stability of other ice shelves, necessitating the continued, close observation of Antarctica's coastline in the future.

Southern Ocean pinnipeds provide bathymetric insights on the East Antarctic continental shelf

Poor coverage of the Antarctic continental shelf bathymetry impedes understanding the oceanographic processes affecting Antarctica’s role in global climate. Continental shelf bathymetry influences warm modified Circumpolar Deep Water movement onto the shelf, making it an important factor promoting ice shelf melting and influencing the flow of ice shelves into the ocean. Building on previous work using seal dives to redefine bathymetry, our longitudinal study of ocean physics and animal behaviour provided new depth information from over 500,000 individual seal dives on the East Antarctic continental shelf. About 25% of these seal dives were 220 m (sometimes over 1000 m) deeper than the interpolated seafloor from IBCSO V2. Focusing on four well-sampled regions, we show that the bathymetry of 22% to 60% of the sampled area was improved by incorporating seal dive data. This revealed new bathymetric features, including troughs off the Shackleton Ice Shelf and Underwood Glacier and a deep canyon near the Vanderford Glacier. This deep canyon, the Mirounga-Nuyina Canyon, was confirmed by a recent multi-beam echo sounder survey. Further acquisitions of seal data will improve our understanding and modelling of Antarctic coastal ocean processes and ice-sheet dynamics.

Marginal Detachment Zones: The Fracture Factories of Ice Shelves?

AbstractAlong the lateral margins of floating ice shelves in Greenland and Antarctica, ice flow past confining margins and pinning points is often accompanied by extensive rifting. Rifts in zones of marginal decoupling (“detachment zones”) typically propagate inward from the margins and result in many of Earth's largest calving events. Velocity maps of detachment zones indicate that flow through these regions is spatially transitioning from confined to unconfined ice shelf flow. We employ the software package icepack to demonstrate that longitudinally decreasing marginal resistance reproduces observed transitions in flow regime, and we show that these spatial transitions are accompanied by near‐margin tension sufficient to explain full‐thickness rifts. Thus, we suggest that zones of progressive decoupling are a primary control on ice shelf calving. The steadiness of detachment zone positions may be a good indicator of ice shelf vulnerability, with migratory or thinning detachment zones indicating shelves at risk of dynamic speedup and increased fracture.

Near-surface seismic anisotropy in Antarctic glacial snow and ice revealed by high-frequency ambient noise

AbstractAmbient seismic recordings taken at broad locations across Ross Ice Shelf and a dense array near West Antarctic Ice Sheet (WAIS) Divide, Antarctica, show pervasive temporally variable resonance peaks associated with trapped seismic waves in near-surface firn layers. These resonance peaks feature splitting on the horizontal components, here interpreted as frequency-dependent anisotropy in the firn and underlying ice due to several overlapping mechanisms driven by ice flow. Frequency peak splitting magnitudes and fast/slow axes were systematically estimated at single stations using a novel algorithm and compared with good agreement with active source anisotropy measurements at WAIS Divide determined via active sources recorded on a 1 km circular array. The approach was further applied to the broad Ross Ice Shelf (RIS) array, where anisotropy axes were directly compared with visible surface features and ice shelf flow lines. The near-surface firn, depicted by anisotropy above 30 Hz, was shown to exhibit a novel plastic stretching mechanism of anisotropy, whereby the fast direction in snow aligns with accelerating ice shelf flow.

Antarctic ice-shelf advance driven by anomalous atmospheric and sea-ice circulation

The disintegration of the eastern Antarctic Peninsula’s Larsen A and B ice shelves has been attributed to atmosphere and ocean warming, and increased mass losses from the glaciers once restrained by these ice shelves have increased Antarctica’s total contribution to sea-level rise. Abrupt recessions in ice-shelf frontal position presaged the break-up of Larsen A and B, yet, in the ~20 years since these events, documented knowledge of frontal change along the entire ~1,400-km-long eastern Antarctic Peninsula is limited. Here, we show that 85% of the seaward ice-shelf perimeter fringing this coastline underwent uninterrupted advance between the early 2000s and 2019, in contrast to the two previous decades. We attribute this advance to enhanced ocean-wave dampening, ice-shelf buttressing and the absence of sea-surface slope-induced gravitational ice-shelf flow. These phenomena were, in turn, enabled by increased near-shore sea ice driven by a Weddell Sea-wide intensification of cyclonic surface winds around 2002. Collectively, our observations demonstrate that sea-ice change can either safeguard from, or set in motion, the final rifting and calving of even large Antarctic ice shelves. Most of the eastern Antarctic Peninsula’s coastline has undergone uninterrupted advance since the early 2000s due to enhanced near-shore sea ice, according to satellite observations and reanalysis data.

Modeling the Deformation Regime of Thwaites Glacier, West Antarctica, Using a Simple Flow Relation for Ice Anisotropy (ESTAR)

AbstractIce deformation dominates the evolution of ice shelf flow and the slow‐moving regions in the interior of ice sheets. However, deformation may be poorly represented in large‐scale ice sheet models that use the Glen flow relation, due to its questionable applicability to the steady‐state flow of anisotropic ice that prevails in ice sheets, having been derived from secondary creep rates of isotropic ice. We assess the deformation regimes of Thwaites Glacier, West Antarctica, using the Glen and “Empirical Scalar Tertiary Anisotropy Regime”, (ESTAR) flow relations, the latter being derived from steady‐state deformation rates of anisotropic ice. For grounded ice, the character of the flow relation determines the contribution of deformation to overall flow, with ESTAR producing greater bed‐parallel shear deformation than the standard Glen flow relation. The ESTAR experiments show larger basal shear stress maxima than the standard Glen experiment because ESTAR treats the responses to simple shear stresses and compression stresses differently, reducing the role of lateral and longitudinal stresses in momentum balance. On the Thwaites Glacier Tongue, ESTAR provides the best match to observed speeds by accounting for the differing effects of stresses on ice flow. Our results highlight the importance of the numerical description of anisotropy, particularly: In regions of transition from deformation‐dominated to sliding‐dominated flow; in the approach to the grounding line, and across ice shelves. Given the importance of these locations in determining mass flux into the ocean, our results have implications for projections of sea level change from Antarctic ice loss.

Controls on Larsen C Ice Shelf Retreat From a 60‐Year Satellite Data Record

AbstractRapid retreat of the Larsen A and B ice shelves has provided important clues about the ice shelf destabilization processes. The Larsen C Ice Shelf, the largest remaining ice shelf on the Antarctic Peninsula, may also be vulnerable to future collapse in a warming climate. Here, we utilize multisource satellite images collected over 1963–2020 to derive multidecadal time series of ice front, flow velocities, and critical rift features over Larsen C, with the aim of understanding the controls on its retreat. We complement these observations with modeling experiments using the Ice‐sheet and Sea‐level System Model to examine how front geometry conditions and mechanical weakening due to rifts affect ice shelf dynamics. Over the past six decades, Larsen C lost over 20% of its area, dominated by rift‐induced tabular iceberg calving. The Bawden Ice Rise and Gipps Ice Rise are critical areas for rift formation, through their impact on the longitudinal deviatoric stress field. Mechanical weakening around Gipps Ice Rise is found to be an important control on localized flow acceleration and the propagation of two rifts that caused a major calving event in 2017. Capturing the time‐varying effects of rifts on ice rigidity in ice shelf models is essential for making realistic predictions of ice shelf flow dynamics and instability. In the context of the Larsen A and Larsen B collapses, we infer a chronology of destabilization processes for embayment‐confined ice shelves, which provides a useful framework for understanding the historical and future destabilization of Antarctic ice shelves.

Bathymetric Control on Borchgrevink and Roi Baudouin Ice Shelves in East Antarctica

AbstractThe stability of ice shelves and drainage of ice sheets they buttress is largely determined by melting at their atmospheric and oceanic interfaces. Subglacial bathymetry can impact ice shelf stability because it influences the onset and the pattern of warm ocean water incursions into the cavities between them and the seafloor. Bathymetry is further important at pinning points, which significantly retard the flow of ice shelves. This effect can be lost instantaneously if basal and surface melting cause an ice sheet to thin and lift off its pinning points. With all this in mind, we have developed a model of bathymetry beneath the western Roi Baudouin and central and eastern Borchgrevink ice shelves in Dronning Maud Land based on inversion from gravity data and tied to available depth references offshore and subglacial topography inland of the grounding line. The model shows deep glacial troughs beneath the ice shelves and bathymetric sills close to the continental shelf. The central Borchgrevink Ice Shelf overhangs the continental slope by around 50 km, exposing its northern parts to the open ocean and higher ocean temperatures. Continuous troughs traverse the central Borchgrevink and western Roi Baudouin ice shelves at depths greater than the offshore thermocline and thus present a risk of Warm Deep Water intrusions into their cavities under the current and future oceanographic regimes. Differing bathymetric characteristics might explain the ice shelves' contrasting dominant mass loss processes.

Mechanics and dynamics of pinning points on the Shirase Coast, West Antarctica

Abstract. Ice rises and rumples, sites of localised ice-shelf grounding, modify ice-shelf flow by generating lateral and basal shear stresses, upstream compression, and downstream tension. Studies of pinning points typically quantify this role indirectly, through related metrics such as a buttressing number. Here, we quantify the dynamic effects of pinning points directly, by comparing model-simulated stress states in the Ross Ice Shelf (RIS) with and without a specific set of pinning points located downstream of the MacAyeal and Bindschadler ice streams (MacIS and BIS, respectively). Because ice properties are only known indirectly, the experiment is repeated with different realisations of the ice softness. While longitudinal stretching, and thus ice velocity, is smaller with the pinning points, flow resistance generated by other grounded features is also smaller. Conversely, flow resistance generated by other grounded features increases when the pinning points are absent, providing a non-local control on the net effect of the pinning points on ice-shelf flow. We find that an ice stream located directly upstream of the pinning points, MacIS, is less responsive to their removal than the obliquely oriented BIS. This response is due to zones of locally higher basal drag acting on MacIS, which may itself be a consequence of the coupled ice-shelf and ice-stream response to the pinning points. We also find that inversion of present-day flow and thickness for basal friction and ice softness, without feature-specific, a posteriori adjustment, leads to the incorrect representation of ice rumple morphology and an incorrect boundary condition at the ice base. Viewed from the perspective of change detection, we find that, following pinning point removal, the ice shelf undergoes an adjustment to a new steady state that involves an initial increase in ice speeds across the eastern ice shelf, followed by decaying flow speeds, as mass flux reduces thickness gradients in some areas and increases thickness gradients in others. Increases in ice-stream flow speeds persist with no further adjustment, even without sustained grounding-line retreat. Where pinning point effects are important, model tuning that respects their morphology is necessary to represent the system as a whole and inform interpretations of observed change.

Treatment of ice-shelf evolution combining flow and flexure

AbstractWe develop a two-dimensional, plan-view formulation of ice-shelf flow and viscoelastic ice-shelf flexure. This formulation combines, for the first time, the shallow-shelf approximation for horizontal ice-shelf flow (and shallow-stream approximation for flow on lubricated beds such as where ice rises and rumples form), with the treatment of a thin-plate flexure. We demonstrate the treatment by performing two finite-element simulations: one of the relict pedestalled lake features that exist on some debris-covered ice shelves due to strong heterogeneity in surface ablation, and the other of ice rumpling in the grounding zone of an ice rise. The proposed treatment opens new venues to investigate physical processes that require coupling between the longitudinal deformation and vertical flexure, for instance, the effects of surface melting and supraglacial lakes on ice shelves, interactions with the sea swell, and many others.

Exploring mechanisms responsible for tidal modulation in flow of the Filchner–Ronne Ice Shelf

Abstract. An extensive network of GPS sites on the Filchner–Ronne Ice Shelf and adjoining ice streams shows strong tidal modulation of horizontal ice flow at a range of frequencies. A particularly strong (horizontal) response is found at the fortnightly (Msf) frequency. Since this tidal constituent is absent in the (vertical) tidal forcing, this observation implies the action of some non-linear mechanism. Another striking aspect is the strong amplitude of the flow perturbation, causing a periodic reversal in the direction of ice shelf flow in some areas and a 10 %–20 % change in speed at grounding lines. No model has yet been able to reproduce the quantitative aspects of the observed tidal modulation across the entire Filchner–Ronne Ice Shelf. The cause of the tidal ice flow response has, therefore, remained an enigma, indicating a serious limitation in our current understanding of the mechanics of large-scale ice flow. A further limitation of previous studies is that they have all focused on isolated regions and interactions between different areas have, therefore, not been fully accounted for. Here, we conduct the first large-scale ice flow modelling study to explore these processes using a viscoelastic rheology and realistic geometry of the entire Filchner–Ronne Ice Shelf, where the best observations of tidal response are available. We evaluate all relevant mechanisms that have hitherto been put forward to explain how tides might affect ice shelf flow and compare our results with observational data. We conclude that, while some are able to generate the correct general qualitative aspects of the tidally induced perturbations in ice flow, most of these mechanisms must be ruled out as being the primary cause of the observed long-period response. We find that only tidally induced lateral migration of grounding lines can generate a sufficiently strong long-period Msf response on the ice shelf to match observations. Furthermore, we show that the observed horizontal short-period semidiurnal tidal motion, causing twice-daily flow reversals at the ice front, can be generated through a purely elastic response to basin-wide tidal perturbations in the ice shelf slope. This model also allows us to quantify the effect of tides on mean ice flow and we find that the Filchner–Ronne Ice Shelf flows, on average, ∼ 21 % faster than it would in the absence of large ocean tides.

Marine ice sheet dynamics: the impacts of ice-shelf buttressing

Marine ice sheets are continent-scale glacial masses that lie partially submerged in the ocean, as applies to significant regions of Antarctica and Greenland. Such ice sheets have the potential to destabilise under a buoyancy-driven instability mechanism, with considerable implications for future sea level. This paper and its companion present a theoretical analysis of marine ice sheet dynamics under the effect of a potentially dominant control of the buttressing force generated by lateral stresses on the downstream floating component of the ice sheet (the ice shelf). The analysis reveals critical conditions under which ice-shelf buttressing suppresses the buoyancy-driven collapse of an ice sheet and elucidates the implications of lateral stresses on grounding-line control and overall ice-sheet structure. Integrations of a suitably simplified quasi-two-dimensional model are conducted, yielding analytical results that provide a quick assessment of steady-state balances for a given ice-sheet configuration. An analytical balance equation describing the spectrum of marine ice sheet flow regimes spanning zero to strong ice-shelf buttressing is developed. It is determined that the dynamics across this spectrum exhibits markedly different flow regimes and structural characteristics. For sufficient buttressing, the grounding line occurs near to where a lateral-drag controlled section of the ice shelf meets the bedrock, implying an independent control of the grounding line by the ice shelf. The role of basal stresses is relegated to controlling only the thickness of the ice sheet upstream of the grounding line, with no significant control of the grounding line itself. It is further demonstrated that lateral stresses are responsible for inducing additional secondary contacts between the ice shelf and the bedrock downstream of the grounding line, resulting in a rich variety of additional steady states. These inducements generate a further stabilising mechanism that can fully suppress grounding-line retreat and eliminate otherwise irreparable hysteresis effects. The results provide a conceptual framework for numerical and observational interpretation of marine ice sheet dynamics, and clarifies the manner in which ice shelves can control grounding-line positions independently. It is thus indicated that a full resolution of the fine details of the flow of ice shelves and the processes controlling their erosion and disintegration is necessary for the confident forecasting of possible ice-sheet collapse over the course of the next few centuries.

The internal structure of the Brunt Ice Shelf from ice-penetrating radar analysis and implications for ice shelf fracture

Abstract. The rate and direction of rift propagation through ice shelves depend on both the stress field and the heterogeneity (or otherwise) of the physical properties of the ice. The Brunt Ice Shelf in Antarctica has recently developed new rifts, which are being actively monitored as they lengthen and interact with the internal structure of the ice shelf. Here we present the results of a ground-penetrating radar survey of the Brunt Ice Shelf aimed at understanding variations in the internal structure. We find that there are flow bands composed mostly of thick (ca. 250 m) meteoric ice interspersed with thinner (ca. 150 m) sections of ice shelf that have a large proportion of sea ice and seawater-saturated firn. Therefore the ice shelf is, in essence, a series of ice tongues cemented together with ice mélange. The changes in structure are related both to the thickness and flow speed of ice at the grounding line and to subsequent processes of firn accumulation and brine infiltration as the ice shelf flows towards the calving front. It is shown that rifts propagating through the Brunt Ice Shelf preferentially skirt the edges of blocks of meteoric ice and slow their rate of propagation when forced by the stress field to break through them, in contrast to the situation on other ice shelves where rift propagation speeds up in meteoric ice.

Tidal bending of ice shelves as a mechanism for large-scale temporal variations in ice flow

Abstract. GPS measurements reveal strong modulation of horizontal ice shelf and ice stream flow at a variety of tidal frequencies, most notably a fortnightly (Msf) frequency not present in the vertical tides themselves. Current theories largely fail to explain the strength and prevalence of this signal over floating ice shelves. We show how well-known non-linear aspects of ice rheology can give rise to widespread, long-periodic tidal modulation in ice shelf flow, generated within ice shelves themselves through tidal flexure acting at diurnal and semidiurnal frequencies. Using full-Stokes viscoelastic modelling, we show that inclusion of tidal bending within the model accounts for much of the observed tidal modulation of ice shelf flow. Furthermore, our model shows that, in the absence of vertical tidal forcing, the mean flow of the ice shelf is reduced by almost 30 % for the geometry that we consider.

Changes in flow of Crosson and Dotson ice shelves, West Antarctica, in response to elevated melt

Abstract. Crosson and Dotson ice shelves are two of the most rapidly changing outlets in West Antarctica, displaying both significant thinning and grounding-line retreat in recent decades. We used remotely sensed measurements of velocity and ice geometry to investigate the processes controlling their changes in speed and grounding-line position over the past 20 years. We combined these observations with inverse modeling of the viscosity of the ice shelves to understand how weakening of the shelves affected this speedup. These ice shelves have lost mass continuously since the 1990s, and we find that this loss results from increasing melt beneath both shelves and the increasing speed of Crosson. High melt rates persisted over the period covered by our observations (1996–2014), with the highest rates beneath areas that ungrounded during this time. Grounding-line flux exceeded basin-wide accumulation by about a factor of 2 throughout the study period, consistent with earlier studies, resulting in significant loss of grounded as well as floating ice. The near doubling of Crosson's speed in some areas during this time is likely the result of weakening of its margins and retreat of its grounding line. This speedup contrasts with Dotson, which has maintained its speed despite increasingly high melt rates near its grounding line, likely a result of the sustained competency of the shelf. Our results indicate that changes to melt rates began before 1996 and suggest that observed increases in melt in the 2000s compounded an ongoing retreat of this system. Advection of a channel along Dotson, as well as the grounding-line position of Kohler Glacier, suggests that Dotson experienced a change in flow around the 1970s, which may be the initial cause of its continuing retreat.

Tidal modulation of ice shelf buttressing stresses

ABSTRACT Ocean tides influence the flow of marine-terminating glaciers. Observations indicate that the large fortnightly variations in ice flow at Rutford Ice Stream in West Antarctica originate in the floating ice shelf. We show that nonlinear variations in ice shelf buttressing driven by tides can produce such fortnightly variations in ice flow. These nonlinearities in the tidal modulation of buttressing stresses can be caused by asymmetries in the contact stress from migration of the grounding line and bathymetric pinning points beneath the ice shelf. Using a simple viscoelastic model, we demonstrate that a combination of buttressing and hydrostatic stress variations can explain a diverse range of tidal variations in ice shelf flow, including the period, phase and amplitude of flow variations observed at Rutford and Bindschadler Ice Streams.

The shape of change: an EOF approach to identifying sources of transient thickness change in an ice shelf

ABSTRACT Ross Ice Shelf (RIS) is known to experience transient thickness change due to changes in the flow of its tributary ice streams and glaciers and this may complicate identification of external, climate-forced signals in contemporary observations of ice shelf thinning and thickening. Flux changes at the lateral boundaries produce both instantaneous and longer timescale adjustments in the coupled velocity and thickness fields. Here, we adapt a statistical approach to output from a numerical model of ice shelf flow to identify characteristic patterns (spatial response surfaces) associated with stepped and cyclic perturbations to boundary fluxes. Once known, characteristic patterns identified in observational data may be attributed to specific sources. An example involving discharge of Byrd Glacier into RIS is described. We find that spatial response surfaces for thickness and velocity generated in individual flow model experiments appear to be independent of flux perturbation shape and magnitude. Additionally, recent acceleration of Byrd Glacier is apparent in ICESat-detected change in RIS thickness.

The dynamics of confined extensional flows

I present a theoretical and experimental study of floating viscous fluid films introduced into a channel of finite length, motivated by the flow of glacial ice shelves. The dynamics are characterized by a mixture of viscous extensional stresses, transverse shear stresses and a driving buoyancy force. A theory based on a width-integrated model is developed and investigated using analytical, asymptotic and numerical methods. With fluid introduced at a constant rate, the flow is found to approach a steady state with two possible asymptotic forms depending on the length of the channel. For channel lengths less than half the width, the flow is similar to a purely extensional one-dimensional flow, characterized by concave surface profiles and being insensitive to the position of the channel exit (or calving front). Greater lengths result in a more complex asymptotic structure in which the flow adjusts over a short distance towards a prevailing flow of universal dimensionless form. In complete contrast to the extensional regime, the prevailing flow is controlled by the position of the channel exit. Data from a new laboratory experiment involving particle velocimetry of a floating fluid film compares well with the predicted along-channel velocity. Motivated by glaciological application, the analysis is generalized to power-law rheologies and the results used to classify the flow regimes of a selection of ice shelves. The prediction for the frontal speed is in good agreement with geophysical data, indicating that the universal profile predicted by the theory is common in nature.

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

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.

Representation of sharp rifts and faults mechanics in modeling ice shelf flow dynamics: Application to Brunt/Stancomb‐Wills Ice Shelf, Antarctica

AbstractIce shelves play a major role in buttressing ice sheet flow into the ocean, hence the importance of accurate numerical modeling of their stress regime. Commonly used ice flow models assume a continuous medium and are therefore complicated by the presence of rupture features (crevasses, rifts, and faults) that significantly affect the overall flow patterns. Here we apply contact mechanics and penalty methods to develop a new ice shelf flow model that captures the impact of rifts and faults on the rheology and stress distribution of ice shelves. The model achieves a best fit solution to satellite observations of ice shelf velocities to infer the following: (1) a spatial distribution of contact and friction points along detected faults and rifts, (2) a more realistic spatial pattern of ice shelf rheology, and (3) a better representation of the stress balance in the immediate vicinity of faults and rifts. Thus, applying the model to the Brunt/Stancomb‐Wills Ice Shelf, Antarctica, we quantify the state of friction inside faults and the opening rates of rifts and obtain an ice shelf rheology that remains relatively constant everywhere else on the ice shelf. We further demonstrate that better stress representation has widespread application in examining aspects affecting ice shelf structure and dynamics including the extent of ice mélange in rifts and the change in fracture configurations. All are major applications for better insight into the important question of ice shelf stability.