scholarly journals An Inter-Comparison of Techniques for Determining Velocities of Maritime Arctic Glaciers, Svalbard, Using Radarsat-2 Wide Fine Mode Data

2016 ◽  
Author(s):  
Thomas Schellenberger ◽  
Wesley Van Wychen ◽  
Luke Copland ◽  
Andreas Kääb ◽  
Laurence Gray
Keyword(s):  
Speckle Tracking ◽  
Ice Sheets ◽  
Synthetic Aperture ◽  
Pixel Resolution ◽  
Tidewater Glaciers ◽  
Ice Caps ◽  
Spatial Coverage ◽  
Fine Mode ◽  
Comparison Of Techniques ◽  
Glacier Velocity

Glacier dynamics play an important role in the mass balance of many glaciers, ice caps and ice sheets. In this study we exploit Radarsat-2 (RS-2) Wide Fine (WF) data to determine the surface speed of Svalbard glaciers in the winters of 2012/2013 and 2013/2014 using Synthetic Aperture RADAR (SAR) offset and speckle tracking. The RS-2 WF mode combines the advantages of the large spatial coverage of the Wide mode (150 x 150 km) and the high pixel resolution (9m) of the Fine mode and thus has a major potential for glacier velocity monitoring from space through offset and speckle tracking. Faster flowing glaciers (1.95 m d-1 - 2.55 m d-1) which are studied in detail are Nathorstbreen, Kronebreen, Kongsbreen and Monacobreen. Using our Radarsat-2 WF dataset, we compare the performance of two SAR tracking algorithms, namely the GAMMA Remote Sensing Software and a custom written MATLAB script (GRAY method) that has primarily been used in the Canadian Arctic. Both algorithms provide comparable results, especially for the faster flowing glaciers and the termini of slower tidewater glaciers. A comparison of the WF data to RS-2 Ultrafine and Wide mode data reveals the superiority of RS-2 WF data over the Wide mode data.

scholarly journals An Inter-Comparison of Techniques for Determining Velocities of Maritime Arctic Glaciers, Svalbard, Using Radarsat-2 Wide Fine Mode Data

2016 ◽  
Author(s):  
Thomas Schellenberger ◽  
Wesley Van Wychen ◽  
Luke Copland ◽  
Andreas Kääb ◽  
Laurence Gray
Keyword(s):  
Speckle Tracking ◽  
Ice Sheets ◽  
Synthetic Aperture ◽  
Pixel Resolution ◽  
Tidewater Glaciers ◽  
Ice Caps ◽  
Spatial Coverage ◽  
Fine Mode ◽  
Comparison Of Techniques ◽  
Glacier Velocity

Glacier dynamics play an important role in the mass balance of many glaciers, ice caps and ice sheets. In this study we exploit Radarsat-2 (RS-2) Wide Fine (WF) data to determine the surface speed of Svalbard glaciers in the winters of 2012/2013 and 2013/2014 using Synthetic Aperture RADAR (SAR) offset and speckle tracking. The RS-2 WF mode combines the advantages of the large spatial coverage of the Wide mode (150 x 150 km) and the high pixel resolution (9m) of the Fine mode and thus has a major potential for glacier velocity monitoring from space through offset and speckle tracking. Faster flowing glaciers (1.95 md-1 - 2.55 md-1) which are studied in more detail are Nathorstbreen, Kronebreen, Kongsbreen and Monacobreen. Using our Radarsat-2 Wide Fine dataset, we compare the performance of two SAR tracking algorithms, namely the GAMMA Remote Sensing Software and a custom written MATLAB script that has primarily been used in the Canadian Arctic. Both algorithms provide comparable results, especially for the faster flowing glaciers and the termini of slower tidewater glaciers. A comparison of the WF data to RS-2 Ultrafine and Wide mode data reveals the superiority of RS-2 WF data over the Wide mode data.

scholarly journals Glacier Flow Dynamics of the Severnaya Zemlya Archipelago in Russian High Arctic Using the Differential SAR Interferometry (DInSAR) Technique

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2466 ◽  
Author(s):  
Nela ◽  
Bandyopadhyay ◽  
Singh ◽  
Glazovsky ◽  
Lavrentiev ◽  
...  
Keyword(s):  
Maximum Velocity ◽  
Lower Surface ◽  
Sar Interferometry ◽  
Surface Velocity ◽  
Ice Caps ◽  
Average Value ◽  
Glacier Velocity ◽  
Severnaya Zemlya ◽  
Academy Of Sciences ◽  
Severnaya Zemlya Archipelago

Glacier velocity is one of the most important parameters to understand glacier dynamics. The Severnaya Zemlya archipelago is host to many glaciers of which four major ice caps encompassing these glaciers are studied, namely, Academy of Sciences, Rusanov, Karpinsky, and University. In this study, we adopted the differential interferometric synthetic aperture radar (DInSAR) method utilizing ALOS-2/PALSAR-2 datasets, with a temporal resolution of 14 days. The observed maximum velocity for one of the marine-terminating glaciers in the Academy of Sciences Ice Cap was 72.24 cm/day (≈263 m/a). For the same glacier, an increment of 3.75 times the flow rate was observed in 23 years, compared to a previous study. This has been attributed to deformation in the bed topography of the glacier. Glaciers in other ice caps showed a comparatively lower surface velocity, ranging from 7.43 to 32.12 cm/day. For estimating the error value in velocity, we selected three ice-free regions and calculated the average value of their observed movement rates by considering the fact that there is zero movement for ice-free areas. The average value observed for the ice-free area was 0.09 cm/day, and we added this value in our uncertainty analysis. Further, it was observed that marine-terminating glaciers have a higher velocity than land-terminating glaciers. Such important observations were identified in this research, which are expected to facilitate future glacier velocity studies.

scholarly journals Equilibrium Profile of Ice Caps

1961 ◽  
Vol 3 (30) ◽  
pp. 953-964 ◽  
Author(s):  
J. Weertman
Keyword(s):  
Creep Rate ◽  
Ice Sheets ◽  
Additional Stress ◽  
Two Dimensional ◽  
Longitudinal Stress ◽  
Sliding Velocity ◽  
Ice Caps ◽  
Ice Cap ◽  
Rate Effects ◽  
Equilibrium Profile

AbstractNye’s theory of the equilibrium profile of two-dimensional ice caps is modified to include longitudinal stress and creep rate effects. A more generalized law for the sliding velocity of a glacier over its bed is introduced into the analysis in order to permit the inclusion of these additional complications. It is found that in the case of small ice caps (of the order of 30 km. in width), it is important to include the longitudinal stress. A somewhat “flatter” profile than that calculated by Nye is obtained. For ice sheets of the dimensions of the Greenland or Antarctic Ice Sheets, the additional stress causes essentially no modification in Nye’s theory. Nye’s theory also has been extended to include an isostatic sinking under the weight of the ice of the bedrock below an ice cap.

scholarly journals A three-dimensional calving model: numerical experiments on Johnsons Glacier, Livingston Island, Antarctica

2010 ◽  
Vol 56 (196) ◽  
pp. 200-214 ◽  
Author(s):  
Jaime Otero ◽  
Francisco J. Navarro ◽  
Carlos Martin ◽  
Maria L. Cuadrado ◽  
Maria I. Corcuera
Keyword(s):  
Three Dimensional ◽  
Ice Sheets ◽  
Prognostic Models ◽  
Current Position ◽  
Polar Ice ◽  
Ice Dynamics ◽  
Ice Shelves ◽  
Tidewater Glaciers ◽  
Livingston Island ◽  
Polar Ice Sheets

AbstractCalving from tidewater glaciers and ice shelves accounts for around half the mass loss from both polar ice sheets, yet the process is not well represented in prognostic models of ice dynamics. Benn and others proposed a calving criterion appropriate for both grounded and floating glacier tongues or ice shelves, based on the penetration depth of transverse crevasses near the calving front, computed using Nye’s formula. The criterion is readily incorporated into glacier and ice-sheet models, but has not been fully validated with observations. We apply a three-dimensional extension of Benn and others’ criterion, incorporated into a full-Stokes model of glacier dynamics, to estimate the current position of the calving front of Johnsons Glacier, Antarctica. We find that two improvements to the original model are necessary to accurately reproduce the observed calving front: (1) computation of the tensile deviatoric stress opening the crevasse using the full-stress solution and (2) consideration of such a tensile stress as a function of depth. Our modelling results also suggest that Johnsons Glacier has a polythermal structure, rather than the temperate structure suggested by earlier studies.

scholarly journals Topography and dynamics of Austfonna, Nordaustlandet, Svalbard, from SAR interferometry

1997 ◽  
Vol 24 ◽  
pp. 403-408 ◽  
Author(s):  
Beverley Unwin ◽  
Duncan Wingham
Keyword(s):  
Sar Interferometry ◽  
Synthetic Aperture ◽  
Drainage Basins ◽  
Ice Caps ◽  
Radar Images ◽  
Differential Interferometry ◽  
Digital Elevation ◽  
Radio Echo Sounding ◽  
Velocity Information ◽  
Elevation Model

The ice caps of Nordaustlandet, Svalbard, represent one of the largest glaciated areas outside of Antarctica and Greenland. They demonstrate a variety of different flow regimes within a comparatively compact area. We report on the first interferometrically derived elevation models and velocity visualisations of Austfonna. This initial investigation had three purposes: to determine whether the coherence and velocity characteristics of the region permitted interferometric survey; to determine the accuracy of derived elevations; and to assess the possibility of investigating time-variant flow of the more dynamic ice bodies using differential interferometry. A trio of coherent synthetic aperture radar images from ERS-1 ’s First Ice Phase was identified. The images were combined to separate the topographic and velocity components of the resultant interferograms. The topographic phase difference was used to produce a digital elevation model of Austfonna. Its accuracy relative to radio-echo-sounding derived tie-points is 8 m and its resolution 40 m. We also present synoptic views of the velocity field of three of Austfonna’s drainage basins, and comment on the extraction of useful velocity information.

Response of faults to climate-driven changes in ice and water volumes on Earth’s surface

2010 ◽  
Vol 368 (1919) ◽  
pp. 2501-2517 ◽  
Author(s):  
Andrea Hampel ◽  
Ralf Hetzel ◽  
Georgios Maniatis
Keyword(s):  
Rate Increase ◽  
Numerical Models ◽  
Ice Sheets ◽  
Slip Rate ◽  
Normal Faults ◽  
Basin And Range Province ◽  
Ice Caps ◽  
Last Glaciation ◽  
Earthquake Frequency ◽  
Water Volumes

Numerical models including one or more faults in a rheologically stratified lithosphere show that climate-induced variations in ice and water volumes on Earth’s surface considerably affect the slip evolution of both thrust and normal faults. In general, the slip rate and hence the seismicity of a fault decreases during loading and increases during unloading. Here, we present several case studies to show that a postglacial slip rate increase occurred on faults worldwide in regions where ice caps and lakes decayed at the end of the last glaciation. Of note is that the postglacial amplification of seismicity was not restricted to the areas beneath the large Laurentide and Fennoscandian ice sheets but also occurred in regions affected by smaller ice caps or lakes, e.g. the Basin-and-Range Province. Our results do not only have important consequences for the interpretation of palaeoseismological records from faults in these regions but also for the evaluation of the future seismicity in regions currently affected by deglaciation like Greenland and Antarctica: shrinkage of the modern ice sheets owing to global warming may ultimately lead to an increase in earthquake frequency in these regions.

scholarly journals Stability of Temperate Ice Caps and Ice Sheets Resting on Beds of Deformable Sediment

1979 ◽  
Vol 24 (90) ◽  
pp. 29-43 ◽  
Author(s):  
G. S Boulton ◽  
A. S Jones
Keyword(s):  
North America ◽  
Ice Sheets ◽  
Surface Profile ◽  
Extreme Case ◽  
Strength Properties ◽  
Ice Shelf ◽  
Forward Movement ◽  
Glacier Surface ◽  
Ice Caps ◽  
Equilibrium Profile

AbstractAlthough theories of glacier movement generally assume that glaciers flow over rigid rock beds, there are many places where glaciers rest on beds of deformable sediment, and the great Pleistocene ice sheets which extended from time to time over much of Northern Europe and North America were largely underlain by such beds. Observations show that a large proportion of the forward movement of a glacier lying on such a bed may be contributed by deformation of the bed rather than the glacier. A theory is developed in which the glacier surface profile is related to the hydraulic and strength properties of potentially deformable bed materials. If these have a high hydraulic transmissibility, melt water is readily discharged sub-glacially, the bed is stable, and the profile is a normal parabolic one, governed by the rhcological properties of ice. If bed transmissibility is low, water pressures build up, the bed begins to deform, and a lower equilibrium profile will develop, so that in an extreme case the glacier approximates to a thin flat sheet, similar to an ice shelf. It is suggested that such behaviour may have occurred at the margins of large Pleistocene ice sheets over North America and Europe, and evidence in support of this is drawn from the reconstructed shapes of these ice margins, anomalously small amounts of isostatic rebound, anomalously high retreat-rates, and the presence of glaciotcctonic structures. Reasons are suggested to explain why this behaviour should have been important for Pleistocene glaciers which penetrated into currently temperate latitudes but does not appear to be important in large modern glaciers.

Three-Dimensional Coastal Geomorphology Deformation Modelling Using Differential Synthetic Aperture Interferometry

2012 ◽  
Vol 67 (6-7) ◽  
pp. 419-420 ◽  
Keyword(s):  
Root Mean Square Error ◽  
Three Dimensional ◽  
Phase Unwrapping ◽  
Coastal Geomorphology ◽  
Synthetic Aperture ◽  
Mean Square ◽  
New Approach ◽  
Deformation Simulation ◽  
Accurate Performance ◽  
Fine Mode

This work presents a new approach for three-dimensional (3D) coastal deformation simulation using differential synthetic aperture interferometry (DInSAR). In doing so, conventional InSAR procedures are implemented to three repeat passes of RADARSAT-1 SAR fine mode data (F1). Further, the DInSAR method is implemented with the phase unwrapping technique. Consequently, DInSAR is used to eliminate the phase decorrelation impact from the interferograms. The study shows the accurate performance of DInSAR with a root mean square error of 0:02 ±0:21 m and 90% confidence intervals. In conclusion, the DInSAR technique produces an accurate 3D coastal geomorphology reconstruction

scholarly journals Early and middle Miocene ice sheet dynamics in the Ross Sea: Results from integrated core-log-seismic interpretation

2021 ◽  
Author(s):  
Lara F. Pérez ◽  
Laura De Santis ◽  
Robert M. McKay ◽  
Robert D. Larter ◽  
Jeanine Ash ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Large Scale ◽  
Middle Miocene ◽  
Ross Sea ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Sediment Supply ◽  
Outer Continental Shelf ◽  
Ice Caps ◽  
Reflection Seismic

Oscillations in ice sheet extent during early and middle Miocene are intermittently preserved in the sedimentary record from the Antarctic continental shelf, with widespread erosion occurring during major ice sheet advances, and open marine deposition during times of ice sheet retreat. Data from seismic reflection surveys and drill sites from Deep Sea Drilling Project Leg 28 and International Ocean Discovery Program Expedition 374, located across the present-day middle continental shelf of the central Ross Sea (Antarctica), indicate the presence of expanded early to middle Miocene sedimentary sections. These include the Miocene climate optimum (MCO ca. 17−14.6 Ma) and the middle Miocene climate transition (MMCT ca. 14.6−13.9 Ma). Here, we correlate drill core records, wireline logs and reflection seismic data to elucidate the depositional architecture of the continental shelf and reconstruct the evolution and variability of dynamic ice sheets in the Ross Sea during the Miocene. Drill-site data are used to constrain seismic isopach maps that document the evolution of different ice sheets and ice caps which influenced sedimentary processes in the Ross Sea through the early to middle Miocene. In the early Miocene, periods of localized advance of the ice margin are revealed by the formation of thick sediment wedges prograding into the basins. At this time, morainal bank complexes are distinguished along the basin margins suggesting sediment supply derived from marine-terminating glaciers. During the MCO, biosiliceous-bearing sediments are regionally mapped within the depocenters of the major sedimentary basin across the Ross Sea, indicative of widespread open marine deposition with reduced glacimarine influence. At the MMCT, a distinct erosive surface is interpreted as representing large-scale marine-based ice sheet advance over most of the Ross Sea paleo-continental shelf. The regional mapping of the seismic stratigraphic architecture and its correlation to drilling data indicate a regional transition through the Miocene from growth of ice caps and inland ice sheets with marine-terminating margins, to widespread marine-based ice sheets extending across the outer continental shelf in the Ross Sea.

scholarly journals Increased West Antarctic ice discharge and East Antarctic stability over the last seven years

2017 ◽  
Author(s):  
Alex S. Gardner ◽  
Geir Moholdt ◽  
Ted Scambos ◽  
Mark Fahnstock ◽  
Stefan Ligtenberg ◽  
...  
Keyword(s):  
Synthetic Aperture Radar ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheets ◽  
Synthetic Aperture ◽  
Direct Role ◽  
Ice Flow ◽  
West Antarctic ◽  
Landsat 7 ◽  
Ice Velocity

Abstract. Ice discharge from large ice sheets plays a direct role in determining rates of sea level rise. We map present-day Antarctic-wide surface velocities using Landsat 7 & 8 imagery spanning 2013–2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since ~ 2008. The new mapping provides complete coastal and inland coverage of ice velocity with a mean error of

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