scholarly journals Surface structure and stability of the Larsen C ice shelf, Antarctic Peninsula

2009 ◽  
Vol 55 (191) ◽  
pp. 400-410 ◽  
Author(s):  
N.F. Glasser ◽  
B. Kulessa ◽  
A. Luckman ◽  
D. Jansen ◽  
E.C. King ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Satellite Image ◽  
Austral Summer ◽  
Shelf Area ◽  
Shelf Edge ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Flow Units ◽  
Grounding Line ◽  
Longitudinal Structures

AbstractA structural glaciological description and analysis of surface morphological features of the Larsen C ice shelf, Antarctic Peninsula, is derived from satellite images spanning the period 1963–2007. The data are evaluated in two time ranges: a comparison of a 1963 satellite image photomosaic with a modern digital mosaic compiled using 2003/04 austral summer data; and an image series since 2003 showing recent evolution of the shelf. We map the ice-shelf edge, rift swarms, crevasses and crevasse traces, and linear longitudinal structures (called ‘flow stripes’ or ‘streak lines’). The latter are observed to be continuous over distances of up to 200 km from the grounding line to the ice-shelf edge, with little evidence of changes in pattern over that distance. Integrated velocity measurements along a flowline indicate that the shelf has been stable for ∼560 years in the mid-shelf area. Linear longitudinal features may be grouped into 12 units, each related to one or a small group of outlet feeder glaciers to the shelf. We observe that the boundaries between these flow units often mark rift terminations. The boundary zones originate upstream at capes, islands or other suture areas between outlet glaciers. In agreement with previous work, our findings imply that rift terminations within such suture zones indicate that they contain anomalously soft ice. We thus suggest that suture zones within the Larsen C ice shelf, and perhaps within ice shelves more generally, may act to stabilize them by reducing regional stress intensities and thus rates of rift lengthening.

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 Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years

2010 ◽  
Vol 4 (1) ◽  
pp. 77-98 ◽  
Author(s):  
A. J. Cook ◽  
D. G. Vaughan
Keyword(s):  
Antarctic Peninsula ◽  
Shelf Area ◽  
Spatial And Temporal Patterns ◽  
Ice Shelf ◽  
Ice Shelves ◽  
The Past ◽  
Predictive Skill ◽  
Dynamics And Control ◽  
And Control ◽  
The Antarctic

Abstract. In recent decades, seven out of twelve ice shelves around the Antarctic Peninsula (AP) have either retreated significantly or have been almost entirely lost. At least some of these retreats have been shown to be unusual within the context of the Holocene and have been widely attributed to recent atmospheric and oceanic changes. To date, measurements of the area of ice shelves on the AP have either been approximated, or calculated for individual shelves over dissimilar time intervals. Here we present a new dataset containing up-to-date and consistent area calculations for each of the twelve ice shelves on the AP over the past five decades. The results reveal an overall reduction in total ice-shelf area by over 28 000 km2 since the beginning of the period. Individual ice shelves show different rates of retreat, ranging from slow but progressive retreat to abrupt collapse. We discuss the pertinent features of each ice shelf and also broad spatial and temporal patterns in the timing and rate of retreat. We believe that an understanding of this diversity and what it implies about the underlying dynamics and control will provide the best foundation for developing a reliable predictive skill for ice-shelf change.

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 Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years

2009 ◽  
Vol 3 (2) ◽  
pp. 579-630 ◽  
Author(s):  
A. J. Cook ◽  
D. G. Vaughan
Keyword(s):  
Antarctic Peninsula ◽  
Shelf Area ◽  
Spatial And Temporal Patterns ◽  
Ice Shelf ◽  
Ice Shelves ◽  
The Past ◽  
Predictive Skill ◽  
Dynamics And Control ◽  
And Control ◽  
The Antarctic

Abstract. In recent decades, seven out of twelve ice shelves around the Antarctic Peninsula (AP) have either retreated significantly or have been almost entirely lost. At least some of these retreats have been shown to be unusual within the context of the Holocene and have been widely attributed to recent atmospheric and oceanic changes. To date, measurements of the area of ice shelves on the AP have either been approximated, or calculated for individual shelves over dissimilar time intervals. Here we present a new dataset containing up-to-date and consistent area calculations for each of the twelve ice shelves on the AP over the past five decades. The results reveal an overall reduction in total ice-shelf area by over 28 000 km2 since the beginning of the period. Individual ice shelves show different rates of retreat, ranging from slow but progressive retreat to abrupt collapse. We discuss the pertinent features of each ice shelf and also broad spatial and temporal patterns in the timing and rate of retreat. We believe that an understanding of this diversity and what it implies about the baseline dynamics and control will provide the best foundation for developing a reliable real predictive skill.

scholarly journals Motion of major ice-shelf fronts in Antarctica from slant-range analysis of radar altimeter data, 1978–98

2002 ◽  
Vol 34 ◽  
pp. 255-262 ◽  
Author(s):  
H.J. Zwally ◽  
M.A. Beckley ◽  
A.C. Brenner ◽  
M.B. Giovinetto
Keyword(s):  
Altimeter Data ◽  
Shelf Area ◽  
Radar Altimeter ◽  
Range Analysis ◽  
Ice Shelf ◽  
The West ◽  
Ice Shelves ◽  
Slant Range ◽  
Grounding Line ◽  
Dronning Maud Land

AbstractSlant-range analysis of radar altimeter data from the Seasat, Geosat and European Remote-sensing Satellite (ERS-1 and -2) databases is used to determine barrier location at particular times, and estimate barrier motion (kma–1) for major Antarctic ice shelves. The analysis covers various multi-year intervals from 1978 to 1998, supplemented by barrier location maps produced elsewhere for 1977 and 1986. Barrier motion is estimated as the ratio between mean annual ice-shelf area change for a particular interval, and the length of the discharge periphery. This value is positive if the barrier location progresses seaward, or negative if the barrier location regresses (break-back). Either positive or negative values are lower-limit estimates because the method does not detect relatively small area changes due to calving or surge events. The findings are discussed in the context of the three ice shelves that lie in large embayments (the Filchner–Ronne, Amery and Ross Ice Shelves), and marginal ice shelves characterized by relatively short distances between main segments of grounding line and barrier (those in the Dronning Maud Land sector between 010.1°W and 032.5°E, and the West and Shackleton Ice Shelves). The ice shelves included in the study account for approximately three-quarters of the total ice-shelf area of Antarctica, and discharge approximately two-thirds of the total grounded ice area.

scholarly journals Recent dynamic changes on Fleming Glacier after the disintegration of Wordie Ice Shelf, Antarctic Peninsula

2017 ◽  
Author(s):  
Peter Friedl ◽  
Thorsten C. Seehaus ◽  
Anja Wendt ◽  
Matthias H. Braun ◽  
Kathrin Höppner
Keyword(s):  
Antarctic Peninsula ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Glacier Tongue ◽  
Bedrock Topography ◽  
Grounding Line ◽  
Glacier Flow ◽  
Western Side ◽  
Continuous Dynamic ◽  
The Antarctic

Abstract. The Antarctic Peninsula is one of the world`s most affected regions by Climate Change. Several ice shelves retreated, thinned or completely disintegrated during recent decades, leading to acceleration and increased calving of their tributary glaciers. Wordie Ice Shelf, located at the south-western side of the Antarctic Peninsula, completely disintegrated in a series of events between the early 1970s and the late 1990s. We investigate the long-term response (1994–2016) of Fleming Glacier after the disintegration of Wordie Ice Shelf by analysing various multi-sensor remote sensing datasets. Our analysis reveals that after two decades of accelerated glacier flow and dynamic thinning the glacier tongue partially ungrounded between January and March 2008. From 2010 to 2011 a further phase of gradual grounding line recession was observed. In total, the retreat of the grounding line between 2008 and 2014 amounted to ~ 6–9 km and caused ~ 68 km2 of the glacier tongue to go afloat. We attribute this to continuous dynamic thinning and pronounced basal melt at the grounding line, probably by a south-western Antarctic Peninsula wide oceanic warming. The bedrock topography revealed that a deep subglacial trough facilitated the grounding line retreat. In response to the ungrounding of the Fleming Glacier tongue we observed an upstream propagation of the acceleration of surface velocities and corresponding to a median speedup along the glacier's centreline of ~ 1.4 m d−1 (~ 29 %) between 2007 and 2011. The propagation of high velocities has not yet affected regions far upstream (~ 50 km) of the glacier. Current ice thinning rates (2011–2014) in areas below 1000 m altitude range between ~ 2.6 to 3.1 m a−1 and are 60–70 % higher than between 2004 and 2008. Our study shows that Fleming Glacier is far away from approaching a new equilibrium and that the glacier dynamics are not primarily controlled by the loss of the ice shelf anymore. Currently, the Fleming Glacier tongue is grounded in a zone of bedrock elevation of ~ −400 m, however, about 3–4 km upstream modelled bedrock topography indicates a retrograde bed which transitions into a deep trough of up to −1000 m at ~ 10 km upstream. Hence, this endangers much larger ice masses in the future and a huge potential for an increase in sea level rise contribution.

scholarly journals An exploratory modelling study of perennial firn aquifers in the Antarctic Peninsula for the period 1979–2016

2021 ◽  
Vol 15 (2) ◽  
pp. 695-714
Author(s):  
J. Melchior van Wessem ◽  
Christian R. Steger ◽  
Nander Wever ◽  
Michiel R. van den Broeke
Keyword(s):  
Antarctic Peninsula ◽  
Climate Model ◽  
Liquid Water Content ◽  
Shelf Area ◽  
Accumulation Rates ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Grid Points ◽  
Western Side ◽  
The Antarctic

Abstract. In this study, we focus on the model detection in the Antarctic Peninsula (AP) of so-called perennial firn aquifers (PFAs) that are widespread in Greenland and Svalbard and are formed when surface meltwater percolates into the firn pack in summer, which is then buried by snowfall and does not refreeze during the following winter. We use two snow models, the Institute for Marine and Atmospheric Research Utrecht Firn Densification Model (IMAU-FDM) and SNOWPACK, and force these (partly) with mass and energy fluxes from the Regional Atmospheric Climate MOdel (RACMO2.3p2) to construct a 1979–2016 climatology of AP firn density, temperature, and liquid water content. An evaluation using 75 snow temperature observations at 10 m depth and density profiles from 11 firn cores shows that output of both snow models is sufficiently realistic to warrant further analysis of firn characteristics. The models give comparable results: in 941 model grid points in either model, covering ∼28 000 km2, PFAs existed for at least 1 year in the simulated period, most notably in the western AP. At these locations, surface meltwater production typically exceeds 200 mmw.e.yr-1, with accumulation for most locations >1000mmw.e.yr-1. Most persistent and extensive are PFAs modelled on and around Wilkins Ice Shelf. Here, both meltwater production and accumulation rates are sufficiently high to sustain a PFA on 49 % of the ice shelf area in (up to) 100 % (depending on the model) of the years in the 1979–2016 period. Although this PFA presence is confirmed by recent observations, its extent in the models appears underestimated. Other notable PFA locations are Wordie Ice Shelf, an ice shelf that has almost completely disappeared in recent decades, and the relatively warm north-western side of mountain ranges in Palmer Land, where accumulation rates can be extremely high, and PFAs are formed frequently. PFAs are not necessarily more frequent in areas with the largest melt and accumulation rates, but they do grow larger and retain more meltwater, which could increase the likelihood of ice shelf hydrofracturing. We find that not only the magnitude of melt and accumulation is important but also the timing of precipitation events relative to melt events. Large accumulation events that occur in the months following an above-average summer melt event favour PFA formation in that year. Most PFAs are predicted near the grounding lines of the (former) Prince Gustav, Wilkins, and Wordie ice shelves. This highlights the need to further investigate how PFAs may impact ice shelf disintegration events through the process of hydrofracturing in a similar way as supraglacial lakes do.

Supraglacial debris along the front of the Larsen-A Ice Shelf, Antarctic Peninsula

2003 ◽  
Vol 15 (4) ◽  
pp. 503-506 ◽  
Author(s):  
JEFFREY EVANS ◽  
COLM Ó COFAIGH
Keyword(s):  
Antarctic Peninsula ◽  
Landsat Imagery ◽  
Coarse Grained ◽  
Continuous Linear ◽  
Polar Ice ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Sea Floor ◽  
Grounding Line ◽  
The Antarctic

Semi-continuous, linear accumulations of poorly-sorted debris are present on the surface of the remnant Larsen-A Ice Shelf, Antarctic Peninsula. These accumulations form a complex of debris bands extending parallel to the front of the ice shelf for several kilometres. Landsat imagery shows that the debris bands originated as lateral moraines along the Nordenskjöld Coast. Almost 80% of clasts sampled from these debris accumulations have shape/roundness characteristics consistent with glacier transport in the zone of basal traction. Angular and very angular clasts account for 15% and 22% of clasts in the pebble- and cobble/boulder-sized fractions, respectively, and originated by rockfall from valley/nunatak sides, with subsequent passive glacier transportation. Lithological analysis indicates that the debris is derived locally from the Nordenskjöld Coast, Cape Fairweather region and interior of the Antarctic Peninsula. Episodic melt-out and resedimentation of this debris from the front of the ice shelf would deliver pulses of coarse-grained sediment to the sea floor. Therefore, coarse-grained debris can also be released along the calving margin of small polar ice shelves fringing mountainous terrain, and could potentially be confused with sediment deposited at the grounding line of Antarctic ice-shelves. Sedimentological criteria to differentiate between these environments are proposed in this paper.

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.

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