Velocities of the Amery Ice Shelf's primary tributary glaciers, 2004–12

M.L. Pittard; J.L. Roberts; C.S. Watson; B.K. Galton-Fenzi; R.C. Warner; R. Coleman

doi:10.1017/s0954102015000231

Velocities of the Amery Ice Shelf's primary tributary glaciers, 2004–12

Antarctic Science ◽

10.1017/s0954102015000231 ◽

2015 ◽

Vol 27 (5) ◽

pp. 511-523 ◽

Cited By ~ 4

Author(s):

M.L. Pittard ◽

J.L. Roberts ◽

C.S. Watson ◽

B.K. Galton-Fenzi ◽

R.C. Warner ◽

...

Keyword(s):

Surface Velocity ◽

Ice Shelf ◽

Ice Flow ◽

Ice Shelves ◽

Ice Surface ◽

Amery Ice Shelf ◽

Landsat 7 ◽

One Year ◽

Shelf Region

AbstractMonitoring the rate of ice flow into ice shelves is vital to understanding how, where and when mass changes occur in Antarctica. Previous observations of ice surface velocity indicate that the Amery Ice Shelf and tributary glaciers have been relatively stable over the period 1968 to 1999. This study measured the displacement of features on the ice surface over a sequence of Landsat 7 images separated by approximately one year and spanning 2004 to 2012 using the surface feature tracking software IMCORR. The focus is on the region surrounding the southern grounding zone of the Amery Ice Shelf and its primary tributary glaciers: the Fisher, Lambert and Mellor glaciers. No significant changes in surface velocity were observed over this period. Accordingly, the velocity fields from each image pair between 2004 and 2012 were used to synthesize an average velocity dataset of the Amery Ice Shelf region and to compare it to previously published velocity datasets and in situ global positioning system velocity observations. No significant change in ice surface velocities was found between 2004 and 2012 in the Amery Ice Shelf region, which suggests that it continues to remain stable.

Mass budget of the grounded ice in the Lambert Glacier–Amery Ice Shelf system

Annals of Glaciology ◽

10.3189/172756408784700644 ◽

2008 ◽

Vol 48 ◽

pp. 193-197 ◽

Cited By ~ 9

Author(s):

Wen Jiahong ◽

Wang Yafeng ◽

Liu Jiying ◽

Kenneth C. Jezek ◽

Philippe Huybrechts ◽

...

Keyword(s):

Accumulation Rate ◽

Surface Velocity ◽

Ice Shelf ◽

Outlet Glacier ◽

Mass Budget ◽

Ice Surface ◽

Amery Ice Shelf ◽

Lambert Glacier ◽

Lambert Glacier Basin

AbstractWe used remote-sensing and in situ measurements of surface accumulation rate, ice surface velocity, thickness and elevation to evaluate the mass budgets of grounded ice-flow regimes that form the Lambert Glacier–Amery Ice Shelf system. Three distinct drainage regimes are considered: the western and eastern margins of the ice shelf, and the southern grounding line at the major outlet glacier confluence, which can be identified with drainage zones 9, 11 and 10 respectively of Giovinetto and Zwally (2000). Our findings show the entire grounded portion of the basin is approximately in balance, with a mass budget of –4.2±9.8 Gt a–1. Drainages 9, 10 and 11 are within balance to the level of our measurement uncertainty, with mass budgets of –2.5±2.8 Gt a–1, –2.6±7.8 Gt a–1 and 0.9±2.3 Gt a–1, respectively. The region upstream of the Australian Lambert Glacier basin (LGB) traverse has a net mass budget of 4.4±6.3 Gt a–1, while the downstream region has –8.9±9.9 Gt a–1. These results indicate that glacier drainages 9, 10 and 11, upstream and downstream of the Australian LGB traverse, are in balance to within our measurement error.

Calving cycle of the Brunt Ice Shelf, Antarctica, driven by changes in ice shelf geometry

The Cryosphere ◽

10.5194/tc-13-2771-2019 ◽

2019 ◽

Vol 13 (10) ◽

pp. 2771-2787 ◽

Cited By ~ 1

Author(s):

Jan De Rydt ◽

Gudmundur Hilmar Gudmundsson ◽

Thomas Nagler ◽

Jan Wuite

Keyword(s):

Large Scale ◽

Ice Shelf ◽

Ice Flow ◽

Ice Shelves ◽

Flow Models ◽

Speed Up ◽

The Antarctic ◽

Detrimental Impact ◽

Natural Laboratory

Abstract. Despite the potentially detrimental impact of large-scale calving events on the geometry and ice flow of the Antarctic Ice Sheet, little is known about the processes that drive rift formation prior to calving, or what controls the timing of these events. The Brunt Ice Shelf in East Antarctica presents a rare natural laboratory to study these processes, following the recent formation of two rifts, each now exceeding 50 km in length. Here we use 2 decades of in situ and remote sensing observations, together with numerical modelling, to reveal how slow changes in ice shelf geometry over time caused build-up of mechanical tension far upstream of the ice front, and culminated in rift formation and a significant speed-up of the ice shelf. These internal feedbacks, whereby ice shelves generate the very conditions that lead to their own (partial) disintegration, are currently missing from ice flow models, which severely limits their ability to accurately predict future sea level rise.

The cavity under the Amery Ice Shelf, East Antarctica

Journal of Glaciology ◽

10.3189/002214308787779898 ◽

2008 ◽

Vol 54 (188) ◽

pp. 881-887 ◽

Cited By ~ 29

Author(s):

B.K. Galton-Fenzi ◽

C. Maraldi ◽

R. Coleman ◽

J. Hunter

Keyword(s):

Water Column ◽

Ocean Circulation ◽

East Antarctica ◽

Ocean Tide ◽

Ice Shelf ◽

Ice Shelves ◽

Ocean Tide Model ◽

Amery Ice Shelf ◽

Tidal Constituents

AbstractOcean circulation under ice shelves and associated rates of melting and freezing are strongly influenced by the shape of the sub-ice-shelf cavity. We have refined an existing method and used additional in situ measurements to estimate the cavity shape under the Amery Ice Shelf, East Antarctica. A finite-element hydrodynamic ocean-tide model was used to simulate the major tidal constituents for a range of different sub-Amery Ice Shelf cavity water-column thicknesses. The data are adjusted in the largely unsurveyed southern region of the ice-shelf cavity by comparing the complex error between simulated tides and in situ tides, derived from GPS observations. We show a significant improvement in the simulated tides, with a combined complex error of 1.8 cm, in comparison with past studies which show a complex error of ∼5.3 cm. Our bathymetry incorporates ice-draft data at the grounding line and seismic surveys, which have provided a considerable amount of new data. This technique has particular application when the water column beneath ice shelves is inaccessible and in situ GPS data are available.

Calving cycle of the Brunt Ice Shelf, Antarctica, driven by changes in ice-shelf geometry

10.5194/tc-2019-46 ◽

2019 ◽

Author(s):

Jan De Rydt ◽

G. Hilmar Gudmundsson ◽

Thomas Nagler ◽

Jan Wuite

Keyword(s):

Large Scale ◽

Ice Shelf ◽

Ice Flow ◽

Ice Shelves ◽

Flow Models ◽

Speed Up ◽

The Antarctic ◽

Detrimental Impact ◽

Natural Laboratory

Abstract. Despite the potentially detrimental impact of large-scale calving events on the geometry and ice flow of the Antarctic Ice Sheet, little is known about the processes that drive rift formation prior to calving, or what controls the timing of these events. The Brunt Ice Shelf in East Antarctica presents a rare natural laboratory to study these processes, following the recent formation of two rifts, each now exceeding 50 km in length. Here we use a unique 50-years' time series of in-situ and remote sensing observations, together with numerical modelling, to reveal how slow changes in ice shelf geometry over time caused build-up of mechanical tension far upstream of the ice front, and culminated in rift formation and a significant speed-up of the ice shelf. These internal feedbacks, whereby ice shelves generate the very conditions that lead to their own (partial) disintegration are currently missing from ice flow models, which severely limits their ability to accurately predict future sea level rise.

SEASONAL COMPARISON OF VELOCITY OF THE EASTERN TRIBUTARY GLACIERS, AMERY ICE SHELF, ANTARCTICA, USING SAR OFFSET TRACKING

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-iv-2-w5-595-2019 ◽

2019 ◽

Vol IV-2/W5 ◽

pp. 595-600

Author(s):

S. D. Jawak ◽

S. Kumar ◽

A. J. Luis ◽

P. H. Pandit ◽

S. F. Wankhede ◽

...

Keyword(s):

Primary Objective ◽

Velocity Estimation ◽

East Antarctica ◽

Surface Velocity ◽

Ice Shelf ◽

Ice Shelves ◽

Tracking Method ◽

Amery Ice Shelf ◽

Glacier Velocity ◽

Offset Tracking

Abstract. Antarctica and Greenland are two major Earth’s continental ice shelves which play an important role in influencing Earth’s energy balance through their high albedo. The ice sheets comprise of grounded ice or the continental glaciers and their associated ice shelves. Surface velocity is an important parameter that needs to be monitored to understand the glacier dynamics. Marine terminating glaciers have higher velocity than land terminating glaciers. Therefore, ice shelves are generally observed to have higher velocity as compared to continental glaciers. The focus of this study is Amery ice shelf (AIS) which is the third largest ice shelf located in east Antarctica terminating into the Prydz Bay on the eastern Antarctica. The surface ice-flow velocity of AIS is very high compared to its surrounding glaciers which flows at a rate of 1400&thinsp;m&thinsp;a&minus;1 and drains about 8% of the Antarctic ice sheet. AIS is fed by different glaciers and ice streams at the head, as well as from the western and eastern side of the ice shelf before it terminates into the ocean. The primary objective of this study was to compute velocity of the eastern tributary glaciers of AIS using SAR from Sentinel-1 data. The secondary objective was to compare the winter and summer velocities of the glaciers for 2017&ndash;2018. The offset tracking method has been applied to the ground range detected (GRD) product obtained from Sentinel-1 satellite. This method is suitable for regions with higher glacier velocity where interferometry is generally affected by the loss of coherence. The offset tracking method works by tracking the features on the basis of another feature and calculates the offset between the two features in the images. Two tributary glaciers near the Clemence massif and another glacier near the Pickering Nunatak feed into this ice shelf from the eastern glacial basin region that drains ice from the American Highland, east Antarctica. The glaciers near the Clemence massif showed low annual velocity which ranged from 100&thinsp;m&thinsp;a&minus;1 at the head to &sim;300&thinsp;m&thinsp;a&minus;1 near the end of the glacier, where it merges with AIS. The glaciers flowing near the Pickering Nunatak exhibited moderate velocity ranging from 150&thinsp;m&thinsp;a&minus;1 at its head and reaching up to 450&thinsp;m&thinsp;a&minus;1 near the tongue. The summer velocity (March 2018) was observed to be higher than the velocity in winter (July 2017) and the difference between the summer and the winter velocities was found to be between 50&thinsp;m&thinsp;a&minus;1 and 130&thinsp;m&thinsp;a&minus;1. The results for the velocity were obtained at 120&thinsp;m resolution and were compared with the previous MEaSUREs (Making Earth System Data Records for Use in Research Environments) yearly velocity at 450&thinsp;m and 1&thinsp;km resolution provided by National Snow and Ice Data Center portal. The results were evaluated using statistical measure- bias and the accuracy was derived using the root mean square error. The bias did not exceed 20&thinsp;m&thinsp;a&minus;1 for the three glaciers and the accuracy was observed to be more than 85% for most of the regions. The accuracy of the results suggests that the offset tracking technique is useful for future velocity estimation in the regions of high glacier velocity.

Monitoring ice shelf velocities from repeat MODIS and Landsat data – a method study on the Larsen C ice shelf, Antarctic Peninsula, and 10 other ice shelves around Antarctica

The Cryosphere ◽

10.5194/tc-4-161-2010 ◽

2010 ◽

Vol 4 (2) ◽

pp. 161-178 ◽

Cited By ~ 46

Author(s):

T. Haug ◽

A. Kääb ◽

P. Skvarca

Keyword(s):

Velocity Field ◽

Spatial Resolution ◽

Antarctic Peninsula ◽

Image Matching ◽

Surface Velocity ◽

Ice Shelf ◽

Ice Shelves ◽

Modis Data ◽

Landsat 7 ◽

Derived Data

Abstract. We investigate the velocity field of the Larsen C ice shelf, Antarctic Peninsula, over the periods 2002–2006 and 2006–2009 based on repeat optical satellite data. The velocity field of the entire ice shelf is measured using repeat low resolution MODIS data (250 m spatial resolution). The measurements are validated for two ice shelf sections against repeat medium resolution Landsat 7 ETM + pan data (15 m spatial resolution). Horizontal surface velocities are obtained through image matching using both orientation correlation operated in the frequency domain and normalized crosscorrelation operated in the spatial domain, and the two methods compared. The uncertainty in the displacement measurements turns out to be about one fourth of the pixel size for the MODIS derived data, and about one pixel for the Landsat derived data. The difference between MODIS and Landsat based speeds is −15.4 m a−1 and 13.0 m a−1, respectively, for the first period for the two different validation sections on the ice shelf, and −26.7 m a−1 and 27.9 m a−1 for the second period for the same sections. This leads us to conclude that repeat MODIS images are well suited to measure ice shelf velocity fields and monitor their changes over time. Orientation correlation seems better suited for this purpose because it produces fewer mismatches, is able to match images with regular noise and data voids, and is faster. Since it can match images with regular data voids it is possible to match Landsat 7 ETM+ images even after the 2003 failure of the Scan Line Corrector (SLC off) that leaves significant image stripes with no data. Image matching based on the original 12-bit radiometric resolution MODIS data produced slightly better results than using the 8-bit version of the same images. Streamline interpolation from the obtained surface velocity field on Larsen C indicates ice travel times of up to 450 to 550 years between the inland boundary and the ice shelf edge. In a second step of the study we test our method successfully on 10 other ice shelves around Antarctica demonstrating that the approach presented could in fact be used for large scale monitoring of ice shelf dynamics.

Evaluation of basal melting parameterisations using in situ ocean and melting observations from the Amery Ice Shelf, East Antarctica

10.5194/os-2021-111 ◽

2021 ◽

Author(s):

Madelaine Gamble Rosevear ◽

Benjamin Keith Galton-Fenzi ◽

Craig Stevens

Keyword(s):

Freezing Point ◽

Acoustic Doppler Current Profiler ◽

Current Speed ◽

East Antarctica ◽

Ice Shelf ◽

Ice Shelves ◽

Amery Ice Shelf ◽

Current Profiler ◽

Basal Melting

Abstract. Ocean driven melting of Antarctic ice shelves is causing grounded ice to be lost from the Antarctic continent at an accelerating rate. However, the ocean processes governing ice shelf melting are not well understood, contributing to uncertainty in projections of Antarctica's contribution to sea level. Here, we analyse oceanographic data and in situ measurements of ice shelf melt collected from an instrumented mooring beneath the centre of the Amery Ice Shelf, East Antarctica. This is the first direct measurement of basal melting from the Amery Ice Shelf, and was made through the novel application of an upwards-facing Acoustic Doppler Current Profiler (ADCP). ADCP data were also used to map a region of the ice base, revealing a steep topographic feature or “scarp” in the ice with vertical and horizontal scales of ~20 m and ~40 m respectively. The annually-averaged ADCP-derived melt rate of 0.51 ± 0.18 m yr−1 is consistent with previous modelling results and glaciological estimates, and there is significant seasonal variation in melting with a maximum in May and a minimum in September. Melting is driven by temperatures ~0.2 °C above the local freezing point and background and tidal currents, which have typical speeds of ~3.0 cm s−1 and 10.0 cm s−1 respectively. We use the coincident measurements of ice shelf melt and oceanographic forcing to evaluate parameterisations of ice-ocean interactions, and find that parameterisations in which there is an explicit dependence of the melt rate on current speed beneath the ice tend to overestimate the local melt rate at AM06 by between 200 % and 400 %, depending on the choice of drag coefficient. A convective parameterisation in which melting is a function of the slope of the ice base is also evaluated and is shown to under-predict melting by 20 % at this site. Using available observations from other ice shelves, we show that a common current speed-dependent parameterisation overestimates melting at all but the coldest, most energetic cavity conditions.

Inferring ice-flow directions from single ice-sheet surface images using the Radon transform

Journal of Glaciology ◽

10.3189/2013jog12j042 ◽

2013 ◽

Vol 59 (213) ◽

pp. 129-136 ◽

Cited By ~ 2

Author(s):

Jason L. Roberts ◽

Roland C. Warner ◽

Adam Treverrow

Keyword(s):

Radon Transform ◽

Flow Direction ◽

Surface Flow ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Landsat 7 ◽

Flow Directions ◽

Direction Fields ◽

Shelf Region ◽

Lambert Glacier

AbstractWe present a new method for extracting the direction of surface flow for ice sheets, based on the detection of flow-induced features that are visible in satellite imagery. The orientation of linear features is determined using a Radon transform and only requires a single image. The technique is demonstrated by applying it to the RADARSAT mosaic of Antarctica, over the Lambert Glacier–Amery Ice Shelf region of East Antarctica. Comparisons with both existing flow-direction fields and traced streamlines over the same area provide an evaluation of the method. We also illustrate its application to Landsat 7 imagery.

Ice shelf history determined from deformation styles in surface debris

Antarctic Science ◽

10.1017/s0954102014000376 ◽

2014 ◽

Vol 26 (6) ◽

pp. 661-673 ◽

Cited By ~ 9

Author(s):

Neil F. Glasser ◽

Tom Holt ◽

Ed Fleming ◽

Carl Stevenson

Keyword(s):

Last Glacial Maximum ◽

Surface Velocity ◽

Velocity Measurements ◽

Ice Shelf ◽

Ice Flow ◽

Ice Surface ◽

Deformational History ◽

Intense Deformation ◽

The Last Glacial Maximum ◽

The Last Glacial

AbstractThis paper presents InSAR-derived ice shelf velocities and observations of surface debris deformation on the McMurdo Ice Shelf (MIS). Ice shelf velocities show that the MIS has a low surface velocity, with debris-laden parts of the ice shelf in the area known as the ‘swirls’ averaging speeds of c. 3 m a-1 increasing to c. 16 m a-1 at the ice front. Analysis of the fold patterns within moraine ridges on the ice surface reveals a deformational history inconsistent with the present velocity measurements. Polyphase, isoclinal folding within moraine ridges at the surface are interpreted to have formed through intense deformation by past ice flow in a NNW orientation. The velocities and styles of deformation indicate that the majority of debris on the ice shelf was originally transported into the area by a large and dynamic ice sheet/ice shelf system entirely different to that of the present configuration. Although the age of this event is unknown, it is possible that this debris has been exposed on the surface of the ice shelf since the last glacial maximum.

Ice loss processes in the Seal Nunataks ice shelf region from satellite altimetry and imagery

Annals of Glaciology ◽

10.1017/aog.2016.29 ◽

2016 ◽

Vol 57 (73) ◽

pp. 94-104 ◽

Cited By ~ 2

Author(s):

Christopher Shuman ◽

Ted Scambos ◽

Etienne Berthier

Keyword(s):

Detailed Analysis ◽

Antarctic Peninsula ◽

Satellite Altimetry ◽

Ice Shelf ◽

Ice Shelves ◽

Landsat 7 ◽

Fast Ice ◽

Shelf Region

ABSTRACTThe Seal Nunataks ice shelf (SNIS, ~743 km2 in 2013) is an unofficial name for a remnant area between the former Larsen A and Larsen B ice shelves off the northeastern Antarctic Peninsula. Analyses using Landsat 7 ETM+ and Terra ASTER images from 2001 to 13 and ICESat altimetry from 2003 to 09 show it has retreated and thinned following the Larsen A (1995) and Larsen B (2002) disintegrations. Despite some regional cooling and more fast ice since 2008, SNIS continues to lose ice along its margins and may be losing contact with some nunataks. Detailed analysis of data from four ICESat tracks indicates that ice shelf thinning rates range between 1.9 and 2.7 m a−1, and generally increase from west to east. An ICESat repeat track crossing the adjacent Robertson Island shows a mean elevation loss of 1.8 m a−1. Two tracks crossing the SNIS's remaining tributary, Rogosh Glacier, show sub-meter elevation losses. Comparing shelf remnant and grounded ice thinning rates implies that basal ocean melting augments SNIS thinning by ~1 m a−1, a rate that is consistent with other estimates of ocean-driven shelf thinning in the region.