Ice velocity changes in the Ross and Ronne sectors observed using satellite radar data from 1997 and 2009

Abstract. We report changes in ice velocity of a 6.5 million km2 region around South Pole encompassing the Filchner-Ronne and Ross Ice Shelves and a significant portion of the ice streams and glaciers that constitute their catchment areas. Using the first full interferometric synthetic aperture radar (InSAR) coverage of the region completed in 2009 and partial coverage acquired in 1997, we processed the data to assemble a comprehensive map of ice speed changes between those two years. On the Ross Ice Shelf, our results confirm a continued deceleration of Mercer and Whillans Ice Streams with a 12-yr velocity difference of −50 m yr−1 (−16.7%) and −100 m yr−1 (−25.3%) at their grounding lines. The deceleration spreads 450 km upstream of the grounding line and more than 500 km onto the shelf, beyond what was previously known. Ross and Filchner Ice Shelves exhibit signs of pre-calving events, representing the largest observed changes, with an increase in speed in excess of +100 m yr−1 in 12 yr. Other changes in the Ross Ice Shelf region are less significant. The observed changes in glacier speed extend on the Ross Ice Shelf along the ice streams' flow lines. Most tributaries of the Filchner-Ronne Ice Shelf show a modest deceleration or no change between 1997 and 2009. Slessor Glacier shows a small deceleration over a large sector. No change is detected on the Bailey, Rutford, and Institute Ice Streams. On the Filchner Ice Shelf itself, ice decelerated rather uniformly with a 12-yr difference in speed of −50 m yr−1, or −5% of its ice front speed, which we attribute to a 12 km advance in its ice front position. Our results show that dynamic changes are present in the region. They highlight the need for continued observation of the area with a primary focus on the Siple Coast. The dynamic changes in Central Antarctica between 1997 and 2009 are generally second-order effects in comparison to losses on glaciers in the Bellingshausen and Amundsen Seas region and on the Antarctic Peninsula. We therefore conclude that the dynamic changes shown here do not have a strong impact on the mass budget of the Antarctic continent.

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Twelve years of ice velocity change in Antarctica observed by RADARSAT-1 and -2 satellite radar interferometry

The Cryosphere Discussions ◽

10.5194/tcd-6-1715-2012 ◽

2012 ◽

Vol 6 (3) ◽

pp. 1715-1738 ◽

Cited By ~ 2

Author(s):

B. Scheuchl ◽

J. Mouginot ◽

E. Rignot

Keyword(s):

Ice Shelf ◽

Ice Streams ◽

Velocity Difference ◽

Velocity Change ◽

Ice Dynamics ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Ice Stream ◽

Catchment Areas ◽

Ice Velocity

Abstract. We report changes in ice velocity of a 6.5 million km2 region around South Pole encompassing the Ronne/Filchner and Ross Ice Shelves and a significant portion of the ice streams and glaciers that constitute their catchment areas. Using the first full interferometric synthetic-aperture radar (InSAR) coverage of the region completed in 2009 and partial coverage acquired in 1997, we process the data to assemble a comprehensive map of ice velocity changes with a nominal precision of detection of &pm;3–4 m yr–1. The largest observed changes, an increase in speed of 100 m yr–1 in 12 yr, are near the frontal regions of the large ice shelves and are associated with the slow detachment of large tabular blocks that will eventually form icebergs. On the Ross Ice Shelf, our data reveal a slow down of Mercer and Whillans Ice Streams with a 12 yr velocity difference of 50 m yr–1 (16.7 %) and 100 m yr–1 (25.3 %) at their grounding lines. The slow down spreads 450 km upstream of the grounding line and more than 500 km onto the shelf, i.e., far beyond what was previously known. Also slowing in the Ross Ice Shelf sector are MacAyeal Ice Stream and Byrd Glacier with a 12 yr velocity difference near their grounding lines of 30 m yr–1 (6.7 %) and 35 m yr–1 (4.1 %), respectively. Bindschadler Ice Stream is faster by 20 m yr–1 (5 %). Most of these changes in glacier speed extend on the Ross Ice Shelf along the ice streams' flow lines. At the mouth of the Filchner/Ronne Ice Shelves, the 12 yr difference in glacier speed is below the 8 % level. We detect the largest slow down with a 12 yr velocity difference of up to 30 m yr–1 on Slessor and Recovery Glaciers, equivalent to 6.7 % and 3.3 %, respectively. Foundation Ice Stream shows a modest speed up (30 m yr–1 or 5 %). No change is detected on Bailey, Rutford, and Institute Ice Streams. On the Filchner Ice Shelf proper, ice slowed down rather uniformly with a 12 yr velocity difference of 50 m yr–1, or 5 % of its ice front speed, which we attribute to an 12 km advance in its ice front position. Overall, we conclude that the ice streams and ice shelves in this broad region, in contrast with their counterparts in the Amundsen and Bellingshausen seas, exhibit changes in ice dynamics that have almost no impact on the overall ice balance of the region.

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Efficient Location and Extraction of the Iceberg Calved Areas of the Antarctic Ice Shelves

Remote Sensing ◽

10.3390/rs12162658 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2658

Author(s):

Mengzhen Qi ◽

Yan Liu ◽

Yijing Lin ◽

Fengming Hui ◽

Teng Li ◽

...

Keyword(s):

Extraction Process ◽

Ice Shelf ◽

Extraction Area ◽

Ice Shelves ◽

Textural Characteristics ◽

Iceberg Calving ◽

Ice Velocity ◽

The Antarctic ◽

Omission Errors

Continuous, rapid, and precise monitoring of calving events contributes to an in-depth understanding of calving mechanisms, which have the potential to cause significant mass loss from the Antarctic ice sheet. The difficulties in the precise monitoring of iceberg calving lie with the coexistence of ice shelf advances and calving. The manual location of iceberg calving is time-consuming and painstaking, while achieving precise extraction has mostly relied on the surface textural characteristics of the ice shelves and the quality of the images. Here, we propose a new and efficient method of separating the expansion and calving processes of ice shelves. We visualized the extension process by simulating a new coastline, based on the ice velocity, and detected the calved area using the simulated coastline and single-temporal post-calving images. We extensively tested the validity of this method by extracting four annual calving datasets (from August 2015 to August 2019) from the Sentinel-1 synthetic aperture radar mosaic of the Antarctic coastline. A total of 2032 annual Antarctic calving events were detected, with areas ranging from 0.05 km2 to 6141.0 km2, occurring on almost every Antarctic ice shelf. The extraction accuracy of the calved area depends on the positioning accuracy of the simulated coastline and the spatial resolution of the images. The positioning error of the simulated coastline is less than one pixel, and the determined minimum valid extraction area is 0.05 km2, when based on 75 m resolution images. Our method effectively avoids repetition and omission errors during the calved area extraction process. Furthermore, its efficiency is not affected by the surface textural characteristics of the calving fronts and the various changes in the frontal edge velocity, which makes it fully applicable to the rapid and accurate extraction of different calving types.

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On the Disintegration of Ice Shelves: the Role of Thinning

Annals of Glaciology ◽

10.1017/s0260305500002676 ◽

1982 ◽

Vol 3 ◽

pp. 146-151 ◽

Cited By ~ 11

Author(s):

T. J. Hughes

Keyword(s):

Weak Links ◽

Ice Melting ◽

Ice Shelf ◽

Ice Streams ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Tidal Pumping ◽

Grounding Line ◽

Converging Flow

It is proposed that an ice shelf disintegrates when its calving front retreats faster than its grounding line. This paper examines the role of ice thinning in grounding-line retreat. Thinning occurs as a result of creep spreading and ice melting. Thinning by creep is examined for the general regime of bending converging flow in an ice shelf lying in a confined embayment, and at the grounding lines of ice streams that supply the ice shelf and ice rises where the ice shelf is grounded on bedrock. Thinning by melting is examined at these grounding lines for tidal pumping and for descent of surface melt water into strandline crevasses, where concentrated melting is focused at the supposed weak links that connect the ice shelf to its embayment, its ice streams, and its ice rises. Applications are made to the Ross Ice 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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Dynamic changes on Wilkins Ice Shelf during the 2006–2009 retreat derived from satellite observations

10.5194/tc-2016-218 ◽

2016 ◽

Author(s):

Melanie Rankl ◽

Johannes Jakob Fürst ◽

Angelika Humbert ◽

Matthias Holger Braun

Keyword(s):

Surface Flow ◽

Satellite Observations ◽

Ice Shelf ◽

Dynamic Changes ◽

Ice Shelves ◽

Multi Stage ◽

Multi Temporal ◽

Horizontal Strain ◽

Offset Tracking ◽

The Antarctic

Abstract. Ice shelves serve as important buttresses for upstream areas. Several large ice shelves on the Antarctic Peninsula have disintegrated or retreated, which implied dynamic consequences for upstream ice. The present study aims to assess dynamic changes on Wilkins Ice Shelf during multi-stage ice-front retreat in the last decade. A total area of 2135 &pm; 75 km2 was lost in the period 2008–2009. The present study uses time-series of SAR satellite observations (1994/96, 2006–2010) in order to derive variations in multi-temporal surface flow from intensity offset tracking methods. Spatial patterns of horizontal strain rate and stress components were inferred during different ice-front retreat stages. These fields are used to explain the different break-up stages and to evaluate the ice-shelf stability. For this purpose, we apply criteria which were forwarded to explain and assess past ice-shelf retreat.

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A Model for Holocene Retreat of the West Antarctic Ice Sheet

Quaternary Research ◽

10.1016/0033-5894(78)90098-4 ◽

1978 ◽

Vol 10 (2) ◽

pp. 150-170 ◽

Cited By ~ 249

Author(s):

Robert H. Thomas ◽

Charles R. Bentley

Keyword(s):

Sea Level ◽

Ice Sheet ◽

Ice Shelf ◽

Ice Streams ◽

The West ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

Ice Shelves ◽

Ross Ice Shelf ◽

West Antarctic

Marine ice sheets are grounded on land which was below sea level before it became depressed under the ice-sheet load. They are inherently unstable and, because of bedrock topography after depression, the collapse of a marine ice sheet may be very rapid. In this paper equations are derived that can be used to make a quantitative estimate of the maximum size of a marine ice sheet and of when and how rapidly retreat would take place under prescribed conditions. Ice-sheet growth is favored by falling sea level and uplift of the seabed. In most cases the buttressing effect of a partially grounded ice shelf is a prerequisite for maximum growth out to the edge of the continental shelf. Collapse is triggered most easily by eustatic rise in sea level, but it is possible that the ice sheet may self-destruct by depressing the edge of the continental shelf so that sea depth is increased at the equilibrium grounding line.Application of the equations to a hypothetical “Ross Ice Sheet” that 18,000 yr ago may have covered the present-day Ross Ice Shelf indicates that, if the ice sheet existed, it probably extended to a line of sills parallel to the edge of the Ross Sea continental shelf. By allowing world sea level to rise from its late-Wisconsin minimum it was possible to calculate retreat rates for individual ice streams that drained the “Ross Ice Sheet.” For all the models tested, retreat began soon after sea level began to rise (∼15,000 yr B.P.). The first 100 km of retreat took between 1500 and 2500 yr but then retreat rates rapidly accelerated to between 0.5 and 25 km yr−1, depending on whether an ice shelf was present or not, with corresponding ice velocities across the grounding line of 4 to 70 km yr−1. All models indicate that most of the present-day Ross Ice Shelf was free of grounded ice by about 7000 yr B.P. As the ice streams retreated floating ice shelves may have formed between promontories of slowly collapsing stagnant ice left behind by the rapidly retreating ice streams. If ice shelves did not form during retreat then the analysis indicates that most of the West Antarctic Ice Sheet would have collapsed by 9000 yr B.P. Thus, the present-day Ross Ice Shelf (and probably the Ronne Ice Shelf) serves to stabilize the West Antarctic Ice Sheet, which would collapse very rapidly if the ice shelves were removed. This provides support for the suggestion that the 6-m sea-level high during the Sangamon Interglacial was caused by collapse of the West Antarctic Ice Sheet after climatic warming had sufficiently weakened the ice shelves. Since the West Antarctic Ice Sheet still exists it seems likely that ice shelves did form during Holocene retreat. Their effect was to slow and, finally, to halt retreat. The models that best fit available data require a rather low shear stress between the ice shelf and its sides, and this implies that rapid shear in this region encouraged the formation of a band of ice with a preferred crystal fabric, as appears to be happening today in the floating portions of fast bounded glaciers.Rebound of the seabed after the ice sheet had retreated to an equilibrium position would allow the ice sheet to advance once more. This may be taking place today since analysis of data from the Ross Ice Shelf indicates that the southeast corner is probably growing thicker with time, and if this persists then large areas of ice shelf must become grounded. This would restrict drainage from West Antarctic ice streams which would tend to thicken and advance their grounding lines into the ice shelf.

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Thermodynamics of the interaction between ice shelves and the sea

Polar Record ◽

10.1017/s0032247400028692 ◽

1976 ◽

Vol 18 (112) ◽

pp. 37-41 ◽

Cited By ~ 39

Author(s):

C. S. M. Doake

Keyword(s):

Ice Sheets ◽

Ice Sheet ◽

Snow Accumulation ◽

Ice Shelf ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Surface Snow ◽

Seaward Edge ◽

The Antarctic

An ice shelf is a floating ice sheet, attached to land where ice is grounded along the coastline. Nourished both by surface snow accumulation and by glaciers and ice sheets flowing off the land, ice shelves can reach a considerable thickness, varying from up to 1 300 m when the ice starts to float to 200 m or less at the seaward edge (known as the ice front). Nearly all the world's ice shelves are found in Antarctica, where they cover an area of about one and a half million square kilometres. The two largest are the Ross Ice Shelf and the Filchner-Ronne ice shelf, each with an area of about half a million square kilometres. Smaller ice shelves fringe other parts of the Antarctic coastline.

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Flow Of Antarctic Ice Shelves Between Long. 29° E. And 44° W

Journal of Glaciology ◽

10.3189/s0022143000015008 ◽

1979 ◽

Vol 24 (90) ◽

pp. 484-485

Author(s):

Olav Orheim

Keyword(s):

Large Mass ◽

Ice Shelf ◽

Ice Streams ◽

Time Intervals ◽

Ice Shelves ◽

Mass Losses ◽

Mass Outflow ◽

Similar Part ◽

The Antarctic ◽

Over Time

This paper discusses the mass outflow and dynamics of a 3000 km long front of the Antarctic ice sheet—the coastline from Prinsesse Ragnhild Kyst to the Filchner Ice Shelf. Ice shelves, mostly 50–100 km wide, account for more than 95% of this coastline. Large mass losses by calving generally occur at intervals of several decades at any particular location, and usually involve shelf areas of 10-1000 km2. The mass loss by calving during the periods between the large calvings is insignificant, except where ice streams run directly into the sea without forming ice shelves. The latter sections account for 2% of the coastline in question and a similar part is made up of ice rises. Thus, with the exception of these short segments, the ice front advances systematically over time intervals of a few decades. Large calvings interrupting the advance can be recognized by significant change in shape and position of the ice front.

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Effect of Improved Bedrock Geometry on Antarctic Vulnerability to Regional Ice Shelf Collapse

10.5194/egusphere-egu2020-10033 ◽

2020 ◽

Author(s):

Daniel Martin ◽

Stephen Cornford ◽

Esmond Ng

Keyword(s):

Recent Work ◽

Sea Level ◽

Ice Sheet ◽

Mass Conservation ◽

West Antarctica ◽

Ice Shelf ◽

Ice Streams ◽

Ice Shelves ◽

Starting Point ◽

The Antarctic

The Antarctic Ice Sheet (AIS) is vulnerable to the thinning or even the collapse of its floating ice shelves, which tend to buttress ice streams. Any reduction in buttressing results in acceleration and thinning upstream and potentially the onset of Marine Ice Sheet Instability. Recent work demonstrates that West Antarctica is vulnerable to sustained disintegration in any of its major marine outlets, resulting in 2-3 m sea level rise over 1000 years. At the same time regions in East Antarctica are vulnerable only to the loss of local ice shelves. However, most of this work has used the Bedmap2 dataset as a starting point. Since the release of Bedmap2 in 2012, there has been a sustained campaign of observations, along with improved interpolation techniques based on mass conservation. The resulting datasets, including the recently released BedMachine dataset, incorporate much-improved bedrock and thickness data compared to what was available in Bedmap2.&#160;We reproduce our previous examination of the millennial-scale vulnerability of the AIS to the loss of its shelves to examine the effect of this improvement on projected Antarctic vulnerability, paying special attention to regions like the Aurora Basin which were under-constrained in Bedmap2.

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Ice Shelves: A Review

Journal of Glaciology ◽

10.1017/s0022143000014799 ◽

1979 ◽

Vol 24 (90) ◽

pp. 273-286 ◽

Cited By ~ 56

Author(s):

Robert H. Thomas

Keyword(s):

Indirect Evidence ◽

Ice Shelf ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Flat Slabs ◽

Amery Ice Shelf ◽

Ice Flows ◽

Shelf Dynamics ◽

The Antarctic ◽

Considerable Detail

AbstractIce shelves form where ice flows off the Antarctic ice sheet onto the sea to produce rather flat slabs of floating ice which, for the theoretician, are the simplest of all large ice masses. Boundary conditions are well defined, conditions change very slowly over distances that are large compared with ice thickness, and horizontal velocities are independent of depth. Unconfined ice shelves can be used as giant creep machines to investigate the ice flow law at low stresses. Further inland, where movement is hampered by obstructions such as grounded ice rises and by shear between the ice shelf and its sides, the ice shelf transmits a backpressure which tends to restrict drainage from the ice sheets that feed it. Wastage from ice shelves is principally by calving and by bottom melting. There has been no direct measurement of bottom-melting rates, but indirect evidence suggests that, near the seaward edges of ice shelves, bottom-melting rates may exceed one metre per year, with significant melting within about 100 km of the ice front. Further inland there may be bottom freezing, and analysis of cores taken from the Amery Ice Shelf indicate that bottom-freezing rates average 0.5 m a–1over a distance of 200 km. Such high freezing-rates are probably exceptional, and, beneath the Ross Ice Shelf, freezing appears to be insignificant even at a distance of 400 km from the ice front.Because of their accessibility ice shelves have been studied in considerable detail, but many problems remain. In particular we need to improve our understanding of basal flux, ice-shelf dynamics near the grounding line, the calving of icebergs, and the state of equilibrium of ice rises. In addition there is a clear need for basic data from the Filchner-Ronne ice shelf.

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