Velocity Anomaly of Campbell Glacier, East Antarctica, Observed by Double-Differential Interferometric SAR and Ice Penetrating Radar

Regional changes in the flow velocity of Antarctic glaciers can affect the ice sheet mass balance and formation of surface crevasses. The velocity anomaly of a glacier can be detected using the Double-Differential Interferometric Synthetic Aperture Radar (DDInSAR) technique that removes the constant displacement in two Differential Interferometric SAR (DInSAR) images at different times and shows only the temporally variable displacement. In this study, two circular-shaped ice-velocity anomalies in Campbell Glacier, East Antarctica, were analyzed by using 13 DDInSAR images generated from COSMO-SkyMED one-day tandem DInSAR images in 2010–2011. The topography of the ice surface and ice bed were obtained from the helicopter-borne Ice Penetrating Radar (IPR) surveys in 2016–2017. Denoted as A and B, the velocity anomalies were in circular shapes with radii of ~800 m, located 14.7 km (A) and 11.3 km (B) upstream from the grounding line of the Campbell Glacier. Velocity anomalies were up to ~1 cm/day for A and ~5 cm/day for B. To investigate the cause of the two velocity anomalies, the ice surface and bed profiles derived from the IPR survey crossing the anomalies were analyzed. The two anomalies lay over a bed hill along the glacial valley where stick-slip and pressure melting can occur, resulting in temporal variation of ice velocity. The bright radar reflection and flat hydraulic head at the ice bed of A observed in the IPR-derived radargram strongly suggested the existence of basal water in a form of reservoir or film, which caused smaller friction and the reduced variation of stick-slip motion compared to B. Crevasses began to appear at B due to tensile stress at the top of the hill and the fast flow downstream. The sporadic shift of the location of anomalies suggests complex pressure melting and transportation of the basal water over the bed hill.

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Decadal GPS-derived ice surface velocity along the transect from Zhongshan Station to and around Dome Argus, East Antarctica, 2005–16

Annals of Glaciology ◽

10.1017/aog.2018.3 ◽

2018 ◽

Vol 59 (76pt1) ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Yang Yuande ◽

Ke Hao ◽

Wang Zemin ◽

Li Fei ◽

Ding Minghu ◽

...

Keyword(s):

High Resolution ◽

Ground Truth ◽

East Antarctica ◽

Surface Velocity ◽

Interferometric Synthetic Aperture Radar ◽

Gps Measurements ◽

Zhongshan Station ◽

Ice Surface ◽

Ice Velocity ◽

Ice Sheet Dynamics

ABSTRACTUsing repeat GPS measurements during 2005–16, we calculated and updated two-dimensional high-resolution decadal ice surface velocity estimates along the traverse route from Zhongshan Station to and around Dome Argus, East Antarctica. Along the 71 sites of the transect, the magnitudes of ice velocity increased from near 0 in Dome Argus to 1, 10 and ~100 m a−1 at the sites DT416, DT333 and LT980, respectively. The comparison between GPS and interferometric synthetic aperture radar (InSAR) derived results agree well when the magnitude of the ice surface velocities is faster than 5 m a−1, and disagree for slower flow velocities. A scale value 1.15 and 0.12 can be applied to InSAR derived results over this region with ice surface velocity larger and <5 m a−1, respectively. We attributed the cause of the discrepancy to the insensitivity of InSAR to the magnitude of low ice surface velocities, thus confirming the importance of GPS fieldwork-based ground truth high-resolution ice velocity estimates to constrain ice-sheet dynamics.

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Satellite Altimeter Results Over East Antarctica

Annals of Glaciology ◽

10.3189/s0260305500002482 ◽

1982 ◽

Vol 3 ◽

pp. 32-35 ◽

Cited By ~ 2

Author(s):

R. L. Brooks

Keyword(s):

Tracking System ◽

Ice Sheet ◽

East Antarctica ◽

Satellite Altimeter ◽

Ice Shelves ◽

Ice Surface ◽

Operational Lifetime ◽

Waveform Retracking ◽

Better Than

During the operational lifetime of the Seasat altimeter from 3 July to 10 October 1978, more than 450 overflights were made over East Antarctica inland to latitude 72°S. An analysis of selected passes over a variety of ice features demonstrates that the oceanographic altimeter performed surprisingly well over the ice sheet and ice shelves, acquiring useful measurements during approximately 70% of each pass. The altimeter's onboard tracking system dampened out the ice-surface elevations, but post-flight retracking of the stored return waveforms reveals excellent ice-surface details. After waveform retracking, the altimeter repeatability is better than ±1 m.

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Basal ice motion and deformation at the ice-sheet margin, West Greenland

Annals of Glaciology ◽

10.3189/172756405781813113 ◽

2005 ◽

Vol 42 ◽

pp. 67-70 ◽

Cited By ~ 5

Author(s):

David M. Chandler ◽

Richard I. Waller ◽

William G. Adam

Keyword(s):

Deformation Mode ◽

Time Intervals ◽

Stick Slip ◽

Active Deformation ◽

West Greenland ◽

Shear Structures ◽

Basal Ice ◽

Ice Velocity ◽

Stick Slip Motion ◽

Slip Motion

AbstractMeasurements of basal ice deformation at the margin of Russell Glacier, West Greenland, have provided an opportunity to gain more insight into basal processes occurring near the margin. The basal ice layer comprises a debris-rich, heterogeneous stratified facies, overlain by a comparatively debris-poor dispersed facies. Ice velocities were obtained from anchors placed in both ice facies, at three sites under 5–15 m ice depth. Mean velocities ranged from 20 to 43 m a–1, and velocity gradients indicate high shear strain rates within the basal ice. Stick–slip motion and diurnal variations were observed during measurements at short (1–5 min) time intervals. Vertical gradients in horizontal ice velocity indicate two modes of deformation: (1) viscous deformation within the stratified ice facies, and (2) shear at the interface between the two basal ice facies. Deformation mode 1 may contribute to the folding and shear structures observed in the stratified facies. Deformation mode 2 may generate the stick–slip motion and be associated with the formation of debris bands. Active deformation close to the margin suggests that structures observed within the basal ice are only partially representative of processes occurring near the bed in areas away from the glacier margin.

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The propagation of a surge front on Bering Glacier, Alaska, 2001–2011

Annals of Glaciology ◽

10.3189/2013aog63a341 ◽

2013 ◽

Vol 54 (63) ◽

pp. 221-228 ◽

Cited By ~ 13

Author(s):

James Turrin ◽

Richard R. Forster ◽

Chris Larsen ◽

Jeanne Sauber

Keyword(s):

Feature Tracking ◽

Average Rate ◽

Surface Velocity ◽

Ablation Zone ◽

Ice Surface ◽

Glacier Terminus ◽

Bering Glacier ◽

Landsat 7 ◽

Ice Velocity ◽

Recent Activity

AbstractBering Glacier, Alaska, USA, has a ∼20 year surge cycle, with its most recent surge reaching the terminus in 2011. To study this most recent activity a time series of ice velocity maps was produced by applying optical feature-tracking methods to Landsat-7 ETM+ imagery spanning 2001-11. The velocity maps show a yearly increase in ice surface velocity associated with the down-glacier movement of a surge front. In 2008/09 the maximum ice surface velocity was 1.5 ±0.017 km a-1 in the mid-ablation zone, which decreased to 1.2 ±0.015 km a-1 in 2009/10 in the lower ablation zone, and then increased to nearly 4.4 ± 0.03 km a-1 in summer 2011 when the surge front reached the glacier terminus. The surge front propagated down-glacier as a kinematic wave at an average rate of 4.4 ±2.0 km a-1 between September 2002 and April 2009, then accelerated to 13.9 ± 2.0 km a-1 as it entered the piedmont lobe between April 2009 and September 2010. The wave seems to have initiated near the confluence of Bering Glacier and Bagley Ice Valley as early as 2001, and the surge was triggered in 2008 further down-glacier in the mid-ablation zone after the wave passed an ice reservoir area.

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Importance of Plastic Deformation in Regelation of Ice

Journal of Glaciology ◽

10.3189/s002214300003015x ◽

1979 ◽

Vol 23 (89) ◽

pp. 422-423

Author(s):

K. Tusima ◽

S. Tozuka

Keyword(s):

Plastic Deformation ◽

Ice Surface ◽

Pressure Melting ◽

The Wire ◽

Hard Balls

AbstractIt is well known that regelation may occur by pressure-melting in front of a wire and refreezing at the rear. The velocity of the wire has been observed to have values ranging from 10–5 to 10–1 mm/s. However, there have always been large discrepancies between experiments and any theory based on this mechanism, and, when moving at a comparable velocity, hard balls slid on an ice surface leave grooves made by plastic deformation. So, we conducted experiments to test whether regelation phenomena might be explained by plastic deformation of ice around the wire.

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Exploring the causes of glacier velocity anomalies in High Mountain Asia: Analysis from the Karakoram, Spiti Lahaul and Eastern Himalaya

10.5194/egusphere-egu21-11907 ◽

2021 ◽

Author(s):

Charlotte S. Curry ◽

Ann V. Rowan ◽

Felix S. L. Ng

Keyword(s):

Large Scale ◽

Flow Line ◽

Eastern Himalaya ◽

High Mountain ◽

Mean Velocity ◽

North West ◽

Velocity Anomaly ◽

Hypsometric Integral ◽

Glacier Velocity ◽

Correlated Parameters

Glaciers in High Mountain Asia (HMA) have been experiencing enhanced mass loss and velocity slowdown since the late 1990s, coincident with rising global and regional temperatures. In each HMA region with distinct climatic characteristics, the dynamical responses of glaciers vary substantially; yet these intra-regional variations are overlooked in regional assessments due to large-scale oversampling. In particular, the role of glacier morphological factors (e.g. size, elevation, hypsometry) in causing the different responses is poorly understood.We investigated the velocity changes of the glaciers in three regions &#8212; the Eastern Himalaya, Spiti Lahaul, and Karakoram &#8212; between 2000 and 2016 in order to understand the key components of glacier sensitivity and their relationship with glacier morphology. Using the NASA Inter-Mission Time Series of Land Ice Velocity and Elevation dataset as input, we extracted glacier-specific velocities (and associated errors) using a bespoke MATLAB script, and compiled these into &#8220;mean annual velocity anomaly&#8221; series following established methods. Anomalies were analysed with glacier morphometric parameters using a linear regression approach, with statistically significant relationships identified.Our results show that mean velocity anomaly within the Eastern Himalaya varies with glacier aspect, with mean annual anomalies of 0.09 &#177; 2.32 m yr-1 per year for north-flowing glaciers and &#8211;0.1 &#177; 1.59 m yr-1 per year for south-flowing glaciers. Glaciers in the Karakoram also show opposing trends, with anomalies of &#8211;0.86 &#177; 5.69 m yr-1 per year and &#8211;3.23 &#177; 2.53 m yr-1 per year in the north west, and 1.00 &#177; 3.80 m yr-1 per year in the south east. Glacier slowdown in Spiti Lahaul is &#8211;0.37 &#177; 4.50 m yr-1 per year, and we do not document contrasts in intra-regional glacier response. Overall, glacier size, minimum elevation and hypsometric integral are the most significantly correlated parameters to mean velocity anomaly. Percentage and area of debris, flow line length, slope and termination environment were also found to be important autocorrelations. Importantly, we find no consistent morphometric interactions contributing to glacier anomaly between all three regions, implying that glacier responses are unique and a cumulative product of their morphometric variability.

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Recent high-resolution Antarctic ice velocity maps reveal increased mass loss in Wilkes Land, East Antarctica

Scientific Reports ◽

10.1038/s41598-018-22765-0 ◽

2018 ◽

Vol 8 (1) ◽

Cited By ~ 17

Author(s):

Qiang Shen ◽

Hansheng Wang ◽

C. K. Shum ◽

Liming Jiang ◽

Hou Tse Hsu ◽

...

Keyword(s):

High Resolution ◽

Mass Loss ◽

East Antarctica ◽

Wilkes Land ◽

Ice Velocity

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Ice-Sheet flow in the Vicinity of Southern Victoria Land, Antarctica: Implications for Glacial Chronology

Journal of Glaciology ◽

10.1017/s0022143000014982 ◽

1979 ◽

Vol 24 (90) ◽

pp. 483

Author(s):

David J. Drewry

Keyword(s):

Ice Sheet ◽

East Antarctica ◽

Small Surface ◽

The North ◽

Ice Surface ◽

Glacial Chronology ◽

Victoria Land ◽

Dry Valley ◽

Radio Echo Sounding ◽

Taylor Glacier

Abstract Systematic radio echo-sounding during three seasons since 1971–72 has produced data on the configuration of the ice sheet in East Antarctica. In the sector extending inland from southern Victoria Land, the ice sheet exhibits a large ridge which drives ice towards David Glacier in the north and Mulock and Byrd Glaciers to the south. Within 100 km of the McMurdo dry-valley region soundings along ten sub-parallel lines (c. 10 km apart) provides detail on ice surface and flow patterns at the ridge tip. A small surface dome lies just inland of Taylor Glacier. The surface drops by 100 m or more before rising to join the major ridge in East Antarctica.

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Measured Velocities of Interior East Antarctica and the State of Mass Balance Within the I.A.G.P. Area

Journal of Glaciology ◽

10.1017/s0022143000014660 ◽

1979 ◽

Vol 24 (90) ◽

pp. 77-87 ◽

Cited By ~ 28

Author(s):

N. W. Young

Keyword(s):

Mass Balance ◽

Total Mass ◽

East Antarctica ◽

Velocity Measurements ◽

Drainage Basins ◽

Mass Budget ◽

Large Sector ◽

Ice Velocity ◽

True Mass ◽

Made In

AbstractRecent measurements of accumulation and ice velocity made in the interior of East Antarctica indicate that a large sector between longitudes 80° E. and 135° E. and north of latitude 80° S. has close to a zero net mass budget. This sector is within the study area for the International Antarctic Glaciological Project (I.A.G.P.) and covers a major portion of the area indicated for projects of special emphasis. Velocity measurements were made at a number of points on a traverse route from Mirny (lat. 66° 33′ S., long. 93°00′ E.) on the coast Dome “C” (lat. 74° 40′ S., long. 124° 00′ E.), in the interior. Accumulation measurements were made along this and other traverse routes, extending as far as Vostok (lat. 78° 28′ S., long. 106° 50′ E.), by a number of methods. These included stake, stratigraphic, isotopic, and totalβ-decay observations. The better accumulation data have allowed a review of the total mass input to be made. The true mass budget has been estimated by comparing velocities, calculated assuming a zero net mass budget with measured velocities along the traverse routes and on a number of the outlet glaciers. For this purpose the area was divided into a number of drainage basins according to outlet at the coast. The area of about 106km2and 150 Gt a−1flux input is drained primarily by three glacier systems of which the Totten accounts for 40% of the flux from 55% of the area; the Vanderford 20% from 15%; and the Scott/Denman 20% from 20%.

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The upper mantle beneath the South Atlantic Ocean, South America and Africa from waveform tomography with massive data sets

Geophysical Journal International ◽

10.1093/gji/ggz574 ◽

2020 ◽

Vol 221 (1) ◽

pp. 178-204 ◽

Cited By ~ 7

Author(s):

N L Celli ◽

S Lebedev ◽

A J Schaeffer ◽

M Ravenna ◽

C Gaina

Keyword(s):

South America ◽

Upper Mantle ◽

High Velocity ◽

South Atlantic ◽

The South ◽

Low Velocity ◽

The West ◽

Velocity Anomaly ◽

Archean Crust ◽

Velocity Anomalies

SUMMARY We present a tomographic model of the crust, upper mantle and transition zone beneath the South Atlantic, South America and Africa. Taking advantage of the recent growth in broadband data sampling, we compute the model using waveform fits of over 1.2 million vertical-component seismograms, obtained with the automated multimode inversion of surface, S and multiple S waves. Each waveform provides a set of linear equations constraining perturbations with respect to a 3-D reference model within an approximate sensitivity volume. We then combine all equations into a large linear system and solve it for a 3-D model of S- and P-wave speeds and azimuthal anisotropy within the crust, upper mantle and uppermost lower mantle. In South America and Africa, our new model SA2019 reveals detailed structure of the lithosphere, with structure of the cratons within the continents much more complex than seen previously. In South America, lower seismic velocities underneath the transbrasilian lineament (TBL) separate the high-velocity anomalies beneath the Amazon Craton from those beneath the São Francisco and Paraná Cratons. We image the buried portions of the Amazon Craton, the thick cratonic lithosphere of the Paraná and Parnaíba Basins and an apparently cratonic block wedged between western Guyana and the slab to the west of it, unexposed at the surface. Thick cratonic lithosphere is absent under the Archean crust of the São Luis, Luis Álves and Rio de La Plata Cratons, next to the continental margin. The Guyana Highlands are underlain by low velocities, indicating hot asthenosphere. In the transition zone, we map the subduction of the Nazca Plate and the Chile Rise under Patagonia. Cratonic lithosphere beneath Africa is more fragmented than seen previously, with separate cratonic units observed within the West African and Congo Cratons, and with cratonic lithosphere absent beneath large portions of Archean crust. We image the lateral extent of the Niassa Craton, hypothesized previously and identify a new unit, the Cubango Craton, near the southeast boundary of the grater Congo Craton, with both of these smaller cratons unexposed at the surface. In the South Atlantic, the model reveals the patterns of interaction between the Mid-Atlantic Ridge (MAR) and the nearby hotspots. Low-velocity anomalies beneath major hotspots extend substantially deeper than those beneath the MAR. The Vema Hotspot, in particular, displays a pronounced low-velocity anomaly under the thick, high-velocity lithosphere of the Cape Basin. A strong low velocity anomaly also underlies the Cameroon Volcanic Line and its offshore extension, between Africa and the MAR. Subtracting the global, age-dependent VS averages from those in the South Atlantic Basins, we observe areas where the cooling lithosphere is locally hotter than average, corresponding to the location of the Tristan da Cunha, Vema and Trindade hotspots. Beneath the anomalously deep Argentine Basin, we image unusually thick, high-velocity lithosphere, which suggests that its anomalously great depth can be explained, at least to a large extent, by isostatic, negative lithospheric buoyancy.

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