scholarly journals Numerical modelling of the historic front variation and the future behaviour of the Pasterze glacier, Austria

1997 ◽  
Vol 24 ◽  
pp. 234-241 ◽  
Author(s):  
Z. Zuo ◽  
J. Oerlemans
Keyword(s):  
Steady State ◽  
Flow Model ◽  
Calibration Method ◽  
Climate Scenarios ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Steady State Condition ◽  
Ice Volume ◽  
Future Warming ◽  
Dynamic Calibration Method

An ice-flow model is used to simulate the front variations of the Pasterze glacier, Austria. The model deals explicitly with the ice flux from sub-streams and tributaries to the main ice stream. The dynamic calibration method adopted successfully calibrates the ice-flow model under a non-steady-state condition. Despite the complexity of the glacier geometry, the ice dynamics of the Pasterze are adequately simulated.Results of the sensitivity experiments suggest that the Pasterze glacier has been in a non-steady state most of the time and has a response time of 34–50 years.Projections of the behaviour of the Pasterze in the next 100 years are made under various climate scenarios. Results suggest that the Pasterze will undergo a substantial retreat if there is future warming. The glacier is likely to retreat 2–5 km by the year 2100. The ice volume could be reduced by 24–63% by the end of the 21st century.

scholarly journals Numerical modelling of the historic front variation and the future behaviour of the Pasterze glacier, Austria

1997 ◽  
Vol 24 ◽  
pp. 234-241 ◽  
Author(s):  
Z. Zuo ◽  
J. Oerlemans
Keyword(s):  
Steady State ◽  
Flow Model ◽  
Calibration Method ◽  
Climate Scenarios ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Steady State Condition ◽  
Ice Volume ◽  
Future Warming ◽  
Dynamic Calibration Method

An ice-flow model is used to simulate the front variations of the Pasterze glacier, Austria. The model deals explicitly with the ice flux from sub-streams and tributaries to the main ice stream. The dynamic calibration method adopted successfully calibrates the ice-flow model under a non-steady-state condition. Despite the complexity of the glacier geometry, the ice dynamics of the Pasterze are adequately simulated. Results of the sensitivity experiments suggest that the Pasterze glacier has been in a non-steady state most of the time and has a response time of 34–50 years. Projections of the behaviour of the Pasterze in the next 100 years are made under various climate scenarios. Results suggest that the Pasterze will undergo a substantial retreat if there is future warming. The glacier is likely to retreat 2–5 km by the year 2100. The ice volume could be reduced by 24–63% by the end of the 21st century.

scholarly journals Basal conditions and ice dynamics inferred from radar-derived internal stratigraphy of the northeast Greenland ice stream

2014 ◽  
Vol 55 (67) ◽  
pp. 127-137 ◽  
Author(s):  
Benjamin A. Keisling ◽  
Knut Christianson ◽  
Richard B. Alley ◽  
Leo E. Peters ◽  
John E.M. Christian ◽  
...  
Keyword(s):  
Steady State ◽  
Additional Data ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Ice Stream ◽  
Radio Echo Sounding ◽  
Ice Flows ◽  
Basal Melting ◽  
Spatially Varying ◽  
Geothermal Flux

AbstractWe analyze the internal stratigraphy in radio-echo sounding data of the northeast Greenland ice stream to infer past and present ice dynamics. In the upper reaches of the ice stream, we propose that shear-margin steady-state folds in internal reflecting horizons (IRHs) form due to the influence of ice flow over spatially varying basal lubrication. IRHs are generally lower in the ice stream than outside, likely because of greater basal melting in the ice stream from enhanced geothermal flux and heat of sliding. Strain-rate modeling of IRHs deposited during the Holocene indicates no recent major changes in ice-stream vigor or extent in this region. Downstream of our survey, IRHs are disrupted as the ice flows into a prominent overdeepening. When combined with additional data from other studies, these data suggest that upstream portions of the ice stream are controlled by variations in basal lubrication whereas downstream portions are confined by basal topography.

scholarly journals Assessing Controls on Ice Dynamics at Crane Glacier, Antarctic Peninsula Using a Numerical Ice Flow Model

2021 ◽  
Author(s):  
Rainey Aberle
Keyword(s):  
Antarctic Peninsula ◽  
Flow Model ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Climate Conditions ◽  
Ice Shelves ◽  
Tidewater Glacier ◽  
Mass Discharge

The widespread retreat of glaciers and the collapse of ice shelves along the Antarctic Peninsula has been attributed to atmospheric and oceanic warming, which promotes mass loss. However, several glaciers on the eastern peninsula that were buttressed by the Larsen A and B ice shelves prior to collapse in 1995 and 2002, respectively, have been advancing in recent years. This asymmetric pattern of rapid retreat and long-term re-advance is similar to the tidewater glacier cycle, which can occur largely independent of climate forcing. Here, I use a width- and depth-integrated numerical ice flow model to investigate glacier response to ice shelf collapse and the influence of changing climate conditions at Crane Glacier, formerly a tributary of the Larsen B ice shelf, over the last ~10 years. Sensitivity tests to explore the influence of perturbations in surface mass balance and submarine melt (up to 10 m a-1) and fresh water impounded in crevasses (up to 10 m) on glacier dynamics reveal that by 2100, the modeled mass discharge ranges from 0.53-98 Gt a-1, with the most substantial changes due to surface melt-induced thinning. My findings suggest that the growth of a floating ice tongue can hinder enhanced flow, allowing the grounding zone to remain steady for many decades, analogous to the advancing stage of the tidewater glacier cycle. Additionally, former tributary glaciers can take several decades to geometrically adjust to ice shelf collapse at their terminal boundary while elevated glacier discharge persists.

scholarly journals Ice flow modelling to constrain the surface mass balance and ice discharge of San Rafael Glacier, Northern Patagonia Icefield

2018 ◽  
Vol 64 (246) ◽  
pp. 568-582 ◽  
Author(s):  
GABRIELA COLLAO-BARRIOS ◽  
FABIEN GILLET-CHAULET ◽  
VINCENT FAVIER ◽  
GINO CASASSA ◽  
ETIENNE BERTHIER ◽  
...  
Keyword(s):  
Mass Balance ◽  
Flow Model ◽  
Surface Velocity ◽  
Shear Stresses ◽  
Surface Mass Balance ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Northern Patagonia ◽  
San Rafael

ABSTRACTWe simulate the ice dynamics of the San Rafael Glacier (SRG) in the Northern Patagonia Icefield (46.7°S, 73.5°W), using glacier geometry obtained by airborne gravity measurements. The full-Stokes ice flow model (Elmer/Ice) is initialized using an inverse method to infer the basal friction coefficient from a satellite-derived surface velocity mosaic. The high surface velocities (7.6 km a−1) near the glacier front are explained by low basal shear stresses (<25 kPa). The modelling results suggest that 98% of the surface velocities are due to basal sliding in the fast-flowing glacier tongue (>1 km a−1). We force the model using different surface mass-balance scenarios taken or adapted from previous studies and geodetic elevation changes between 2000 and 2012. Our results suggest that previous estimates of average surface mass balance over the entire glacier (Ḃ) were likely too high, mainly due to an overestimation in the accumulation area. We propose that most of SRG imbalance is due to the large ice discharge (−0.83 ± 0.08 Gt a−1) and a slightly positiveḂ(0.08 ± 0.06 Gt a−1). The committed mass-loss estimate over the next century is −0.34 ± 0.03 Gt a−1. This study demonstrates that surface mass-balance estimates and glacier wastage projections can be improved using a physically based ice flow model.

scholarly journals A two-dimensional shallow ice-flow model of Glacier de Saint-Sorlin, France

2003 ◽  
Vol 49 (167) ◽  
pp. 527-538 ◽  
Author(s):  
Emmanuel Le Meur ◽  
Christian Vincent
Keyword(s):  
Steady State ◽  
20Th Century ◽  
Flow Rate ◽  
Flow Model ◽  
Parameter Study ◽  
Two Dimensional ◽  
Zeroth Order ◽  
Ice Flow ◽  
Glacier Changes ◽  
Bedrock Surface

AbstractA two-dimensional ice-flow model based on the shallow-ice approximation (SIA) is used to investigate the dynamics of Glacier de Saint-Sorlin, France. This glacier is well suited for this kind of study. First, the particular geometry of the glacier itself as well as that of the bedrock surface allows for correct applicability of the SIA (zeroth-order equations), provided that thickness changes and termini positions rather than short-scale dynamics are considered. Secondly, the wealth of available data for the glacier including mass-balance series and records of glacier changes provides a reliable forcing and a powerful constraining set for the model. Steady-state simulations show realistic results and the capabilities of the model in reproducing the glacier extent at the beginning of the 20th century. An extensive parameter study of ice rheology and sliding intensity is also carried out and the results are checked against the thickness changes as well as the glacier termini positions since 1905. It is possible to find a parameter combination that best matches these two types of data with an ice-flow rate factor of 2 × 10−24 Pa−3 s−1 and a Weertman-type sliding factor of 5 × 10−14 m8 N−3 a−1 which both appear to be in agreement with similar inferences from recent modelling attempts.

scholarly journals Space geodesy as a tool for measuring ice surface velocity in the Dome C region and along the ITASE traverse

2004 ◽  
Vol 39 ◽  
pp. 402-408 ◽  
Author(s):  
Luca Vittuari ◽  
Christian Vincent ◽  
Massimo Frezzotti ◽  
Francesco Mancini ◽  
Stefano Gandolfi ◽  
...  
Keyword(s):  
Steady State ◽  
Ice Sheet ◽  
Surface Flow ◽  
State Condition ◽  
Surface Velocity ◽  
Ice Dynamics ◽  
Steady State Condition ◽  
Terra Nova Bay ◽  
Ice Surface ◽  
Terra Nova

AbstractDome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for the drilling of a deep ice core. This paper presents results from geodetic surveys of ice velocities (absolute and relative) at Dome C and along a transect to Terra Nova Bay. The purpose of the surveys was to provide accurate data for the study of ice dynamics, particularly a strain network comprising 37 poles surveyed in 1995 and again in 1999. Data indicate that the ice surface at the poles closest to the topographic summit moves horizontally by up to a few mm a–1 in a direction consistent with downslope motion of the ice sheet, while 25 km from the summit it moves up to 211 mma–1. The EPICA drilling site yields an interpolated velocity of about 15 ±10mma–1 in a north-northwesterly direction. Analysis of the velocity field and surface topography reveals that the surface flow centre is nearly co-located with the dome summit, and that both are in a steady-state condition. The measured horizontal velocities are consistent with the remote-sensing result and provide accurate ground-truth control for flow mapping. Seven snow–firn cores, up to 53m deep, were drilled during the Terra Nova Bay–Dome C traverse. Submerged velocity systems were installed at the borehole and measured using the global positioning system (GPS). First results show a steady-state condition. Measured (horizontal) ice velocities increase from the summit of the ice sheet to the coast, reaching about 28 ma–1 at site GPS2A.

scholarly journals Ice-flow sensitivity to boundary processes: a coupled model study in the Vostok Subglacial Lake area, Antarctica

2012 ◽  
Vol 53 (60) ◽  
pp. 173-180 ◽  
Author(s):  
Malte Thoma ◽  
Klaus Grosfeld ◽  
Christoph Mayer ◽  
Frank Pattyn
Keyword(s):  
Boundary Condition ◽  
Flow Model ◽  
Ice Sheet ◽  
Diagnostic Study ◽  
Lake Area ◽  
Lake Ice ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Subglacial Lake ◽  
Highly Nonlinear

AbstractSeveral hundred subglacial lakes have been identified beneath Antarctica so far. Their interaction with the overlying ice sheet and their influence on ice dynamics are still subjects of investigation. While it is known that lakes reduce the ice-sheet friction towards a free-slip basal boundary condition, little is known about how basal melting and freezing at the lake/ice interface modifies the ice dynamics, thermal regime and ice rheology. In this diagnostic study we simulate the Vostok Subglacial Lake area with a coupled full Stokes 3-D ice-flow model and a 3-D lake-circulation model. The exchange of energy (heat) and mass at the lake/ice interface increases (decreases) the temperature in the ice column above the lake by up to 10% in freezing (melting) areas, resulting in a significant modification of the highly nonlinear ice viscosity. We show that basal lubrication at the bottom of the ice sheet has a significant impact not only on the ice flow above the lake itself, but also on the vicinity and far field. While the ice flow crosses Vostok Subglacial Lake, flow divergence is observed and modelled. The heterogeneous basal-mass-balance pattern at the lake/ice interface intensifies this divergence. Instead of interactive coupling between the ice-flow model and the lake-flow model, only a single iteration is required for a realistic representation of the ice/water interaction. In addition, our study indicates that simplified parameterizations of the surface temperature boundary condition might lead to a velocity error of 20% for the area of investigation.

scholarly journals The response of a simple Antarctic ice-flow model to temperature and sea-level fluctuations over the Cenozoic era

2007 ◽  
Vol 46 ◽  
pp. 69-77 ◽  
Author(s):  
C.I. Van Tuyll ◽  
R.S.W. Van De Wal ◽  
J. Oerlemans
Keyword(s):  
Sea Level ◽  
Deep Sea ◽  
Flow Model ◽  
Ice Sheet ◽  
Temperature Record ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Sea Temperature ◽  
Ice Volume ◽  
The Antarctic

AbstractAn ice-flow model is used to simulate the Antarctic ice-sheet volume and deep-sea temperature record during Cenozoic times. We used a vertically integrated axisymmetric ice-sheet model, including bedrock adjustment. In order to overcome strong numerical hysteresis effects during climate change, the model is solved on a stretching grid. The Cenozoic reconstruction of the Antarctic ice sheet is accomplished by splitting the global oxygen isotope record derived from benthic foraminifera into an ice-volume and a deep-sea temperature component. The model is tuned to reconstruct the initiation of a large ice sheet of continental size at 34 Ma. The resulting ice volume curve shows that small ice caps (<107 km3) could have existed during Paleocene and Eocene times. Fluctuations during the Miocene are large, indicating a retreat back from the coast and a vanishing ice flux across the grounding line, but with ice volumes still up to 60% of the present-day volume. The resulting deep-sea temperature curve shows similarities with the paleotemperature curve derived from Mg/Ca in benthic calcite from 25 Ma till the present, which supports the idea that the ice volume is well reproduced for this period. Before 34 Ma, the reproduced deep-sea temperature is slightly higher than is generally assumed. Global sea-level change turns out to be of minor importance when considering the Cenozoic evolution of the ice sheet until 5 Ma.

scholarly journals Ice-dynamic projections of the Greenland ice sheet in response to atmospheric and oceanic warming

2014 ◽  
Vol 8 (4) ◽  
pp. 3851-3905 ◽  
Author(s):  
J. J. Fürst ◽  
H. Goelzer ◽  
P. Huybrechts
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Flow Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Melting ◽  
Strong Impact ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Over Time

Abstract. Continuing global warming will have a strong impact on the Greenland ice sheet in the coming centuries. During the last decade, both increased surface melting and enhanced ice discharge from calving glaciers have contributed 0.6 ± 0.1 mm yr−1 to global sea-level rise, roughly in shares of respectively 60 and 40 per cent. Here we use a higher-order ice flow model, initialised to the present state, to simulate future ice volume changes driven by both atmospheric and oceanic temperature changes. For these projections, the ice flow model accounts for runoff-induced basal lubrication and ocean warming-induced discharge increase at the marine margins. For a suite of ten Atmosphere and Ocean General Circulation Models and four Representative Concentration Pathway scenarios, the projected sea-level rise lies in the range of +1.4 to +16.6 cm by the year 2100. For two low emission scenarios, the projections are conducted up to 2300. Ice loss rates are found to either abate when the warming already peaks in this century, allowing to preserve the ice sheet in a geometry close to the present-day state, or to remain at a constant level over three hundred years under moderate warming. The volume loss is predominantly caused by increased surface melting as the contribution from enhanced ice discharge decreases over time and is self-limited by thinning and retreat of the marine margin reducing the ice–ocean contact area. The effect of enhanced basal lubrication on the volume evolution is found to be negligible on centennial time scales. The presented projections show that the observed rates of volume change over the last decades cannot simply be extrapolated over the 21st century on account of a different balance of processes causing ice loss over time. The results also indicate that the largest source of uncertainty arises from the surface mass balance and the underlying climate change projections, and not from ice dynamics.

scholarly journals Application of GRACE to the evaluation of an ice flow model of the Greenland Ice Sheet

2016 ◽  
Author(s):  
N.-J. Schlegel ◽  
D. N. Wiese ◽  
E. Y. Larour ◽  
M. M. Watkins ◽  
J. E. Box ◽  
...  
Keyword(s):  
Mass Balance ◽  
Flow Model ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Validation Data ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass

Abstract. Quantifying the Greenland Ice Sheet’s future contribution to sea level rise is a challenging task that requires accurate estimates of ice flow sensitivity to climate change. Forward models of ice flow dynamics are promising tools for estimating future ice sheet behavior, yet confidence is low because evaluation of historical simulations is so challenging due to the scarcity of highly-resolved (spatially and temporally) continental-wide validation data. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained mass concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of estimated monthly global gravity fields. Specifically, the Jet Propulsion Laboratory’s JPL RL05M GRACE mascon solution (GRACE-JPL) now offers an opportunity for ice sheet model evaluation within independently resolved 300 km mascons. Here, we investigate how Greenland Ice Sheet mass balance captured through observations - GRACE-JPL - differs from that simulated by the ice flow model - the Ice Sheet System Model (ISSM). For the years 2003-2012, ISSM is forced with regional climate model (RCM) surface mass balance (SMB), and resulting mass balance is directly compared against GRACE-JPL within individual mascons. Overall, we find good agreement in the Northeast, Southwest, and the interior of the ice sheet, where mass balance is primarily controlled by SMB. In the Northwest, seasonal amplitudes match well, but trends in ISSM are muted relative to GRACE-JPL. In the Southeast, GRACE-JPL exhibits larger seasonal amplitude than that predicted by SMB while simultaneously having more pronounced trends. These results indicate that discrepancies in the Northwest are controlled by changes in ice dynamics that are not currently modeled by ISSM, i.e. transient processes driven by ice sheet hydrology and ice-ocean interaction, while discrepancies in the Southeast are controlled by a combination of these missing dynamics and errors in modeled SMB. Along the margins, we find that transient dynamics are responsible for consistent intra-annual variations in regional mass balance that ultimately contribute to the steeper negative mass trends observed by GRACE-JPL. Consequently, ice-ocean interactions and hydrologically-driven processes at relatively high (monthly-to-seasonal) temporal resolutions must be considered for improving upon ice flow models.

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