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 Climatic conditions, mass balance and dynamics of Larsen B ice shelf, Antarctic Peninsula, prior to collapse

2004 ◽  
Vol 39 ◽  
pp. 557-562 ◽  
Author(s):  
Pedro Skvarca ◽  
Hernán De Angelis ◽  
Andrés F. Zakrajsek
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
Satellite Image ◽  
Climatic Conditions ◽  
Strain Rates ◽  
Ice Shelf ◽  
Ice Flow ◽  
Ice Shelves ◽  
Additional Information ◽  
Significant Acceleration

AbstractFollowing the collapse of Larsen A in 1995, about 3200 km2 of Larsen B ice shelf disintegrated in early 2002 during the warmest summer recorded on the northeastern Antarctic Peninsula. Immediately prior to disintegration the last field campaign was carried out on Larsen B. Measurements included surface net mass balance, velocity and strain rate on a longitudinal transect along Crane Glacier flowline and over a remnant section confined within Seal Nunataks that survived the collapse. In addition, an automatic weather station located nearby allowed derivation of melt days relevant to the formation and extent of surface meltwater. Repeated surveys allowed us to detect a significant acceleration in ice-flow velocity and associated increasing strain rates along the longitudinal transect. It may be possible to use this acceleration as a predictor of imminent ice-shelf collapse, applicable to ice shelves subject to similar climatic conditions. Additional information on recent ongoing changes was provided by a visible satellite image acquired in early 2003.

scholarly journals Recent ice-surface-elevation changes of Fleming Glacier in response to the removal of the Wordie Ice Shelf, Antarctic Peninsula

2010 ◽  
Vol 51 (55) ◽  
pp. 97-102 ◽  
Author(s):  
J. Wendt ◽  
A. Rivera ◽  
A. Wendt ◽  
F. Bown ◽  
R. Zamora ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Regional Climate ◽  
Airborne Lidar ◽  
Similar Data ◽  
Ice Shelf ◽  
International Polar Year ◽  
Ice Flow ◽  
Ice Shelves ◽  
Elevation Changes ◽  
The Antarctic

AbstractRegional climate warming has caused several ice shelves on the Antarctic Peninsula to retreat and ultimately collapse during recent decades. Glaciers flowing into these retreating ice shelves have responded with accelerating ice flow and thinning. The Wordie Ice Shelf on the west coast of the Antarctic Peninsula was reported to have undergone a major areal reduction before 1989. Since then, this ice shelf has continued to retreat and now very little floating ice remains. Little information is currently available regarding the dynamic response of the glaciers feeding the Wordie Ice Shelf, but we describe a Chilean International Polar Year project, initiated in 2007, targeted at studying the glacier dynamics in this area and their relationship to local meteorological conditions. Various data were collected during field campaigns to Fleming Glacier in the austral summers of 2007/08 and 2008/09. In situ measurements of ice-flow velocity first made in 1974 were repeated and these confirm satellite-based assessments that velocity on the glacier has increased by 40–50% since 1974. Airborne lidar data collected in December 2008 can be compared with similar data collected in 2004 in collaboration with NASA and the Chilean Navy. This comparison indicates continued thinning of the glacier, with increasing rates of thinning downstream, with a mean of 4.1 ± 0.2 m a−1 at the grounding line of the glacier. These comparisons give little indication that the glacier is achieving a new equilibrium.

scholarly journals Marine Ice Sheet Instability and Ice Shelf Buttressing Influenced Deglaciation of the Minch Ice Stream, Northwest Scotland

2018 ◽  
Author(s):  
Niall Gandy ◽  
Lauren J. Gregoire ◽  
Jeremy C. Ely ◽  
Christopher D. Clark ◽  
David M. Hodgson ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Ice Shelf ◽  
Dynamical Processes ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Shelves ◽  
Ice Stream ◽  
The Last Deglaciation

Abstract. Uncertainties in future sea level projections are dominated by our limited understanding of the dynamical processes that control instabilities of marine ice sheets. A valuable case to examine these processes is the last deglaciation of the British-Irish Ice Sheet. The Minch Ice Stream, which drained a large proportion of ice from the northwest sector of the British-Irish Ice Sheet during the last deglaciation, is well constrained, with abundant empirical data which could be used to inform, validate and analyse numerical ice sheet simulations. We use BISICLES, a higher-order ice sheet model, to examine the dynamical processes that controlled the retreat of the Minch Ice Stream. We simulate retreat from the shelf edge under constant "warm" surface mass balance and subshelf melt, to isolate the role of internal ice dynamics from external forcings. The model simulates a slowdown of retreat as the ice stream becomes laterally confined at a "pinning-point" between mainland Scotland and the Isle of Lewis. At this stage, the presence of ice shelves became a major control on deglaciation, providing buttressing to upstream ice. Subsequently, the presence of a reverse slope inside the Minch Strait produces an acceleration in retreat, leading to a "collapsed" state, even when the climate returns to the initial "cold" conditions. Our simulations demonstrate the importance of the Marine Ice Sheet Instability and ice shelf buttressing during the deglaciation of parts of the British-Irish Ice Sheet. Thus, geological data could be used to constrain these processes in ice sheet models used for projecting the future of our contemporary ice sheets.

Constraining ice shelf basalt melting rates from isochrone data

2021 ◽  
Author(s):  
Vjeran Visnjevic ◽  
Reinhard Drews ◽  
Clemens Schannwell ◽  
Inka Koch
Keyword(s):  
Ocean Circulation ◽  
Radar Data ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Ice Shelves ◽  
Inverse Approach ◽  
History Of ◽  
Forward And Inverse Modeling ◽  
Basal Melting

<p>Ice shelves buttress ice flow from the continent towards the ocean, and their disintegration results in increased ice discharge.  Ice-shelf evolution and integrity is influenced by surface accumulation, basal melting, and ice dynamics. We find signals of all of these processes imprinted in the ice-shelf stratigraphy that can be mapped using isochrones imaged with radar.</p><p>Our aim is to develop an inverse approach to infer ice shelf basal melt rates using radar isochrones as observational constraints. Here, we investigate the influence of basalt melt rates on the shape of isochrones using combined insights from both forward and inverse modeling. We use the 3D full Stokes model Elmer/Ice in our forward simulations, aiming to reproduce isochrone patterns observed in our data. Moreover we develop an inverse approach based on the shallow shelf approximating, aiming to constrain basal melt rates using isochronal radar data and surface velocities. Insights obtained from our simulations can also guide the collection of new radar data (e.g., profile lines along vs. across-flow) in a way that ambiguities in interpreting the ice-shelf stratigraphy can be minimized. Eventually, combining these approaches will enable us to better constrain the magnitude and history of basal melting, which will give valuable input for ocean circulation and sea level rise projections.</p>

The effect of Antarctic ice-shelf extent on ice discharge

2021 ◽  
Author(s):  
Jim Jordan ◽  
HIlmar Gudmundsson ◽  
Adrian Jenkins ◽  
Chris Stokes ◽  
Stewart Jamiesson ◽  
...  
Keyword(s):  
Mass Loss ◽  
Recent Work ◽  
Flow Model ◽  
Ice Shelf ◽  
Geophysical Research ◽  
Ice Flow ◽  
Ice Shelves ◽  
Grounding Line ◽  
Natural Variance ◽  
Observational Record

<div>The buttressing strength of Antarctic ice shelves directly effects the amount of ice discharge across the grounding line, with buttressing strength affected by both the thickness and extent of an ice shelf. Recent work has shown that a reduction in ice-shelf buttressing due to ocean induced ice-shelf thinning is responsible for a significant portion of increased Antarctic ice discharge (Gudmundsson et al., 2019, but few studies have attempted to show the effect of variability in ice-shelf extent on ice discharge. This variability arises due to ice-shelf calving following a cycle of long periods of slow, continuous calving interposed with calving of large, discrete sections.  These discrete calving events tend to occur on a comparative timeframe to that of the observational record. As such, when determining observed changes in ice discharge it is crucial that this natural variability is separated from any observed trends.  </div><div> </div><div>In this work we use the numerical ice-flow model Úa in combination with observations of ice shelf extent to diagnostically calculate Antarctic ice discharge. These observations primarily date back to the 1970s, though for some ice shelves records exist back to the 1940s. We assemble an Antarctic wide model for two scenarios: 1) with ice shelves at their maximum observed extent and 2) with ice shelves at their minimum observed extent. We then compare these two scenarios to differences in the observed changes in Antarctic ice-discharge to determine how much can be attributed to natural variance .</div><p> </p><p><span>Gudmundsson, G. H.</span><span>, Paolo, F. S., Adusumilli, S., & Fricker, H. A. (2019). </span>Instantaneous Antarctic ice‐ sheet mass loss driven by thinning ice shelves. <em>Geophysical Research Letters</em>, 46, 13903– 13909. </p>

scholarly journals Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

2020 ◽  
Vol 66 (260) ◽  
pp. 1064-1078
Author(s):  
Vikram Goel ◽  
Kenichi Matsuoka ◽  
Cesar Deschamps Berger ◽  
Ian Lee ◽  
Jørgen Dall ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ice Cores ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Shelves ◽  
The Past ◽  
Dronning Maud Land ◽  
The Antarctic

AbstractIce rises and rumples, locally grounded features adjacent to ice shelves, are relatively small yet play significant roles in Antarctic ice dynamics. Their roles generally depend upon their location within the ice shelf and the stage of the ice-sheet retreat or advance. Large, long-stable ice rises can be excellent sites for deep ice coring and paleoclimate study of the Antarctic coast and the Southern Ocean, while small ice rises tend to respond more promptly and can be used to reveal recent changes in regional mass balance. The coasts of Dronning Maud Land (DML) and Enderby Land in East Antarctica are abundant with these features. Here we review existing knowledge, presenting an up-to-date status of research in these regions with focus on ice rises and rumples. We use regional datasets (satellite imagery, surface mass balance and ice thickness) to analyze the extent and surface morphology of ice shelves and characteristic timescales of ice rises. We find that large parts of DML have been changing over the past several millennia. Based on our findings, we highlight ice rises suitable for drilling ice cores for paleoclimate studies as well as ice rises suitable for deciphering ice dynamics and evolution in the region.

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 Present stability of the Larsen C ice shelf, Antarctic Peninsula

2010 ◽  
Vol 56 (198) ◽  
pp. 593-600 ◽  
Author(s):  
D. Jansen ◽  
B. Kulessa ◽  
P.R. Sammonds ◽  
A. Luckman ◽  
E.C. King ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Austral Summer ◽  
Ice Shelf ◽  
Ice Flow ◽  
Seismic Reflection Data ◽  
Ice Shelves ◽  
Reflection Data ◽  
The Moment ◽  
Depth Relationship ◽  
Flow Velocities

AbstractWe modelled the flow of the Larsen C and northernmost Larsen D ice shelves, Antarctic Peninsula, using a model of continuum mechanics of ice flow, and applied a fracture criterion to the simulated velocities to investigate the ice shelf’s present-day stability. Constraints come from satellite data and geophysical measurements from the 2008/09 austral summer. Ice-shelf thickness was derived from BEDMAP and ICESat data, and the density–depth relationship was inferred from our in situ seismic reflection data. We obtained excellent agreements between modelled and measured ice-flow velocities, and inferred and observed distributions of rifts and crevasses. Residual discrepancies between regions of predicted fracture and observed crevasses are concentrated in zones where we assume a significant amount of marine ice and therefore altered mechanical properties in the ice column. This emphasizes the importance of these zones and shows that more data are needed to understand their influence on ice-shelf stability. Modelled flow velocities and the corresponding stress distribution indicate that the Larsen C ice shelf is stable at the moment. However, weakening of the elongated marine ice zones could lead to acceleration of the ice shelf due to decoupling from the slower parts in the northern inlets and south of Kenyon Peninsula, leading to a velocity distribution similar to that in the Larsen B ice shelf prior to its disintegration.

scholarly journals Climatically induced retreat and collapse of northern Larsen Ice Shelf, Antarctic Peninsula

1998 ◽  
Vol 27 ◽  
pp. 86-92 ◽  
Author(s):  
Helmut Rott ◽  
Wolfgang Rack ◽  
Thomas Nagler ◽  
Pedro Skvarca
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
High Sensitivity ◽  
Ice Shelf ◽  
Landsat Images ◽  
Surface Mass ◽  
Ice Shelves ◽  
Radar Images ◽  
Near Future ◽  
Larsen Ice Shelf

The areal changes of the northern Larsen Ite Shelf (LIS), Antarctic Peninsula, between March 1986 and March 1997 have been analyzed, based on synthetic aperture radar images of the European remote-sensing satellites ERS-1 and ERS-2 and on Landsat images. This analysis is complemented by data on ice motion and surface mass balance which have been obtained during several field campaigns since the early 1980s. After a period of retreat, coinciding with atmospheric warming and with decreasing net accumulation at the surface due to melt losses, the two northernmost sections of LIS disintegrated almost completely within a few days in January 1995. Recent observations of the ice-shelf section north of Jason Peninsula, which is presently the northernmost section of LIS, show increased summer melt and intensification of the rifting processes, probably causing accelerated retreat of this section in the near future. The retreat and the disintegration event of LIS indicate high sensitivity of ice shelves to prolonged perturbations of the mass balance.

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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