Coastal-change and glaciological map of the Ronne Ice Shelf area, Antarctica, 1974-2002

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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Ice Movement Studies on the Skelton Glacier

Journal of Glaciology ◽

10.3189/s0022143000027258 ◽

1961 ◽

Vol 3 (29) ◽

pp. 873-878

Author(s):

Charles R. Wilson ◽

A. P. Crary

Keyword(s):

Ross Sea ◽

Ice Thickness ◽

Strain Rates ◽

Shelf Area ◽

Dry Valleys ◽

Ice Shelf ◽

The West ◽

Ross Ice Shelf ◽

High Plateau ◽

Plateau Area

The volume of ice that flows annually from the Skelton Glacier on the west side of the Ross Ice Shelf between the Worcester and Royal Society Ranges was determined during 1958–59 traverse operations to be approximately 791 × 106 m.3 or 712 × 106 m.3 water equivalent. Annual accumulation on the Skelton névé field and small cirque glaciers is estimated to be 1,018 × 106 m.3 water equivalent, but this figure can be reduced to 712 × 106 m.3 by assuming that 30 per cent of the expected accumulation in the lower slopes of the glacier is lost to adjacent areas of the Ross Ice Shelf by katabatic winds. It is evident that little or no contribution to the nourishment of the Skelton Glacier comes from the high plateau area of East Antarctica. It is suggested that this condition exists generally in the western Ross Sea and Ross Shelf area, and is responsible for the existence of the present “dry” valleys in the McMurdo Sound area.Some estimates of local ice regime are made at two sites on the glacier where ice thickness and strain rates are known.

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Assessment of historical changes (1959-2012) and the causes of recent break-ups of the Petersen ice shelf, Nunavut, Canada

Annals of Glaciology ◽

10.3189/2015aog69a687 ◽

2015 ◽

Vol 56 (69) ◽

pp. 65-76 ◽

Cited By ~ 11

Author(s):

Adrienne White ◽

Luke Copland ◽

Derek Mueller ◽

Wesley Van Wychen

Keyword(s):

Loss Rate ◽

Open Water ◽

Shelf Area ◽

Ice Shelf ◽

Pack Ice ◽

The Mean ◽

Landfast Sea Ice ◽

Ice Pressure ◽

Ground Penetrating ◽

Thickness Measurements

AbstractAerial photography and satellite imagery of the Petersen ice shelf, Nunavut, Canada, from 1959 to 2012 show that it was stable until June 2005, after which a series of major calving events in the summers of 2005, 2008, 2011 and 2012 resulted in the loss of ∼61% of the June 2005 ice-shelf area. This recent series of calving events was initiated by the loss of extensive regions of ˃50-year-old multi-year landfast sea ice from the front of the ice shelf in summer 2005. Each subsequent calving event has been preceded by open-water conditions and resulting loss of pack-ice pressure across the front of the ice shelf, and most occurred during record warm summers. Ground-penetrating radar (GPR) ice thickness measurements and RADARSAT-2 derived observations of surface motion indicate that tributary glaciers provided total ice input of 1.19-5.65 Mta–1 to the ice shelf from 2011 to 2012, far below the mean surface loss rate of 28.45 Mta–1. With recent losses due to calving and little evidence for current basal freeze-on, this suggests that the Petersen ice shelf will no longer exist by the 2040s, or sooner if further major calving events occur.

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Isostatic Equilibrium Grounding Line Between The West Antarctic Ice Sheet And The Ross Ice Shelf

Journal of Glaciology ◽

10.1017/s0022143000015082 ◽

1979 ◽

Vol 24 (90) ◽

pp. 500 ◽

Cited By ~ 1

Author(s):

C. R. Bentley ◽

L. Greischar

Keyword(s):

Ice Sheet ◽

Shelf Area ◽

Ice Shelf ◽

Ice Streams ◽

West Antarctic Ice Sheet ◽

Ross Ice Shelf ◽

Isostatic Rebound ◽

West Antarctic ◽

Grounding Line ◽

Eastern Half

Abstract Taking various retreat-rates for the presumed grounded ice sheet in the Ross embayment during Wisconsin time, as calculated by Thomas (Thomas and Bentley, 1978), and assuming a time constant of 4400 years for isostatic rebound, a sea-floor uplift of 100±50 m still to be expected in the grid western part of the Ross Ice Shelf can be calculated. The expected uplift diminishes from grid west to grid east, and is probably negligible in the eastern half of the shelf area. There are extensive areas near the present grounding line where the water depth beneath the shelf is less than 100 m, so that uplift would lead to grounding. As grounding occurred, the neighboring ice shelf would thicken, causing grounding to advance farther. This process would probably extend the grounding line to a position running grid north-eastward across the shelf from the seaward end of Roosevelt Island, deeply indented by the extensions of the present ice streams. Floating ice would remain in the grid south-eastern half of the shelf.

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Two decades of Antarctic coastal-change revealed by satellite imagery and deep learning

10.5194/egusphere-egu21-5344 ◽

2021 ◽

Author(s):

Celia A. Baumhoer ◽

Andreas Dietz ◽

Mariel Dirscherl ◽

Claudia Kuenzer

Keyword(s):

Deep Learning ◽

Ice Sheet ◽

Continuous Mapping ◽

Coastal Change ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Wilkes Land ◽

The Antarctic

Antarctica&#8217;s coastline is constantly changing by moving glacier and ice shelf fronts. The extent of glaciers and ice shelves influences the ice discharge and sea level contribution of the Antarctic Ice Sheet. Therefore, it is crucial to assess where ice shelf areas with strong buttressing forces are lost. So far, those changes have not been assessed for entire Antarctica within comparable time frames.We present a framework for circum-Antarctic coastline extraction based on a U-Net architecture. Antarctic coastal-change is calculated by using a deep learning derived coastline for the year 2018 in combination with earlier manual derived coastlines of 1997 and 2009. For the first time, this allows to compare circum-Antarctic changes in glacier and ice shelf front position for the last two decades. We found that the Antarctic Ice Sheet area decreased by -29,618&#177;1,193 km2 in extent between 1997-2008 and gained an area of 7,108&#177;1,029km2 between 2009 and 2018. Retreat dominated for the Antarctic Peninsula and West Antarctica and advance for the East Antarctic Ice Sheet over the entire investigation period. The only exception in East Antarctica was Wilkes Land experiencing simultaneous calving front retreat of several glaciers between 2009-2018. Biggest tabular iceberg calving events occurred at Ronne and Ross Ice Shelf within their natural calving cycle between 1997-2008. Future work includes the continuous mapping of Antarctica&#8217;s coastal-change on a more frequent temporal scale. &#160;

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Investigating the climate variability in the Totten area using NEMO-LIM regional model.

10.5194/egusphere-egu2020-8075 ◽

2020 ◽

Author(s):

Guillian Van Achter ◽

Charles Pelletier ◽

Thierry Fichefet

Keyword(s):

Sea Ice ◽

Ocean Circulation ◽

Ice Sheet ◽

Regional Model ◽

East Antarctica ◽

Shelf Area ◽

Ice Shelf ◽

Ice Shelves ◽

Landfast Ice ◽

The Impact

The Totten ice shelf drains over 570 000 km&#178; of East Antarctica. Most of the ice sheet that drains through the Totten ice-shelf is from Aurora Subglacial Basin and is marine based making the region potentially vulnerable to rapid ice sheet colapse. Understanding how the changes in ocean circulation and properties are causing increased basal melt of Antarctic ice shelves is crucial for predicting future sea level rise. In the context of the The PARAMOUR project (decadal predictability and variability of polar climate: the role of atmosphere-ocean-cryosphere multiscale interaction), we use a high resolution NEMO-LIM 3.6 regional model to investigate the variability and the predictability of the coupled climate system over the Totten area in East Antarctica. In this poster, we will present our on-going work about the impact of landfast ice over the variability of the system. Landfast ice is sea ice that is fastened to the coastline, to the sea floor along shoals or to grouded icebergs. Current sea ice models are unable to represent very crudely the formation, maintenance and decay of coastal landfast ice. We applyed several parameterization for modeling landfast ice over the Totten ice shelf area.

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Dynamic changes on the Wilkins Ice Shelf during the 2006–2009 retreat derived from satellite observations

The Cryosphere ◽

10.5194/tc-11-1199-2017 ◽

2017 ◽

Vol 11 (3) ◽

pp. 1199-1211 ◽

Cited By ~ 5

Author(s):

Melanie Rankl ◽

Johannes Jakob Fürst ◽

Angelika Humbert ◽

Matthias Holger Braun

Keyword(s):

Time Series ◽

Satellite Observations ◽

Principal Strain ◽

Strain Rates ◽

Shelf Area ◽

Ice Shelf ◽

Dynamic Changes ◽

Flow Angle ◽

Ice Shelves ◽

Stress Flow

Abstract. The vast ice shelves around Antarctica provide significant restraint to the outflow from adjacent tributary glaciers. This important buttressing effect became apparent in the last decades, when outlet glaciers accelerated considerably after several ice shelves were lost around the Antarctic Peninsula (AP). The present study aims to assess dynamic changes on the Wilkins Ice Shelf (WIS) during different stages of ice-front retreat and partial collapse between early 2008 and 2009. The total ice-shelf area lost in these events was 2135 ± 75 km2 ( ∼  15 % of the ice-shelf area relative to 2007). Here, we use time series of synthetic aperture radar (SAR) satellite observations (1994–1996, 2006–2010) in order to derive variations in surface-flow speed from intensity-offset tracking. Spatial patterns of horizontal strain-rate, stress and stress-flow angle distributions are determined during different ice-front retreat stages. Prior to the final break up of an ice bridge in 2008, a strong speed up is observed, which is also discernible from other derived quantities. We identify areas that are important for buttressing and areas prone to fracturing using in-flow and first principal strain rates as well as principal stress components. Further propagation of fractures can be explained as the first principal components of strain rates and stresses exceed documented threshold values. Positive second principal stresses are another scale-free indicator for ice-shelf areas, where fractures preferentially open. Second principal strain rates are found to be insensitive to ice-front retreat or fracturing. Changes in stress-flow angles highlight similar areas as the in-flow strain rates but are difficult to interpret. Our study reveals the large potential of modern SAR satellite time series to better understand dynamic and structural changes during ice-shelf retreat but also points to uncertainties introduced by the methods applied.

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