scholarly journals Three-dimensional glacier surface motion maps at the Gjálp eruption site, Iceland, inferred from combining InSAR and other ice-displacement data

2002 ◽  
Vol 34 ◽  
pp. 315-322 ◽  
Author(s):  
Sverrir Gudmundsson ◽  
Magnus Tumi Gudmundsson ◽  
Helgi Björnsson ◽  
Freysteinn Sigmundsson ◽  
Helmut Rott ◽  
...  
Keyword(s):  
Time Series ◽  
Simulated Annealing Algorithm ◽  
Three Dimensional ◽  
Motion Field ◽  
Glacier Surface ◽  
Ice Flow ◽  
Surface Motion ◽  
Elevation Data ◽  
The Difference ◽  
Basal Melting

AbstractWe use topographically corrected interferograms, repeated global positioning system observations of locations of stakes and time series of elevation data to produce time series of high-resolution three-dimensional (3-D) ice surface motion maps for the infilling of the ice depression created by the 1996 subglacial eruption at the Gjálp volcano in Vatnajökull, Iceland. The ice inflow generated uplift in the central parts of the depression. During the first months, the uplift was much reduced by basal melting as the subglacial volcano cooled. For those motions surface-parallel ice flow cannot be assumed. The 3-D motion maps are created by an optimization process that combines the complementary datasets. The optimization is based on a Markov random-field regularization and a simulated annealing algorithm. The 3-D motion maps show the pattern of gradually diminishing ice flow into the depression. They provide a consistent picture of the 3-D motion field, both spatially and with time, which cannot be seen by separate interpretation of the complementary observations. The 3-D motion maps were used to calculate the cooling rate of the subglacial volcano for the first year after the eruption. First an uplift rate resulting solely from the inflow of ice was calculated from inferred horizontal motions. Basal melting was then estimated as the difference between the calculated uplift generated by the inflow of ice, and the observed uplift that was the combined result of ice inflow and basal melting. The basal melting was found to decline from 55 m3 s–1 (due to power of 18 GW) in January 1997 to 5 m3 s–1 (2GW) in October 1997.

scholarly journals Comparison of direct and geodetic mass balances on an annual time scale

2011 ◽  
Vol 5 (1) ◽  
pp. 565-604 ◽  
Author(s):  
A. Fischer ◽  
H. Schneider ◽  
G. Merkel ◽  
R. Sailer
Keyword(s):  
Mass Balance ◽  
Flow Velocity ◽  
Volume Change ◽  
Glacier Surface ◽  
Ice Flow ◽  
Total Period ◽  
Elevation Data ◽  
Order Of Magnitude ◽  
The Difference ◽  
Geodetic Mass Balance

Abstract. Very accurate airborne laserscanning (ALS) elevation data was used to calculate the annual volume changes for Hintereisferner and Kesselwandferner in the Ötztal Alps, Austria for 2001/2002–2008/2009. The comparison of the altitude of 51 recently GPS surveyed ground control points showed that the accuracy of the ALS DEMs is better than 0.3 m. The geodetic mass balance was calculated from the volume change using detailed maps of the firn cover and applying corrections for the seasonal snow cover. The maximum snow height at the time of the elevation data flight was 0.5 m averaged over the glacier surface. The volume change data was compared to in situ mass balance data for the total area and at the stakes. For the total period of 8 yr, the difference between the geodetic and the direct mass balance is 2.398 m w.e. on Hintereisferner and 1.380 m w.e. on Kesselwandferner, corresponding to about two times the mean annual mass balance. The vertical ice flow velocity was measured and found to be on the same order of magnitude as the mass balance at KWF. This is an indicator that volume change data does not allow the calculation of ablation or accumulation rates without detailed measurements or models of the vertical ice flow velocity. Therefore, only direct mass balance data allow process studies or investigation of the climatic controls of the resulting mass changes.

scholarly journals Three-dimensional deformation time series of glacier motion from multiple-aperture DInSAR observation

2019 ◽  
Vol 93 (12) ◽  
pp. 2651-2660 ◽  
Author(s):  
Sergey Samsonov
Keyword(s):  
Time Series ◽  
Surface Deformation ◽  
Ground Deformation ◽  
Three Dimensional ◽  
Data Sets ◽  
Ice Flow ◽  
The North ◽  
Glacier Ice ◽  
Deformation Component ◽  
3D Deformation

AbstractThe previously presented Multidimensional Small Baseline Subset (MSBAS-2D) technique computes two-dimensional (2D), east and vertical, ground deformation time series from two or more ascending and descending Differential Interferometric Synthetic Aperture Radar (DInSAR) data sets by assuming that the contribution of the north deformation component is negligible. DInSAR data sets can be acquired with different temporal and spatial resolutions, viewing geometries and wavelengths. The MSBAS-2D technique has previously been used for mapping deformation due to mining, urban development, carbon sequestration, permafrost aggradation and pingo growth, and volcanic activities. In the case of glacier ice flow, the north deformation component is often too large to be negligible. Historically, the surface-parallel flow (SPF) constraint was used to compute the static three-dimensional (3D) velocity field at various glaciers. A novel MSBAS-3D technique has been developed for computing 3D deformation time series where the SPF constraint is utilized. This technique is used for mapping 3D deformation at the Barnes Ice Cap, Baffin Island, Nunavut, Canada, during January–March 2015, and the MSBAS-2D and MSBAS-3D solutions are compared. The MSBAS-3D technique can be used for studying glacier ice flow at other glaciers and other surface deformation processes with large north deformation component, such as landslides. The software implementation of MSBAS-3D technique can be downloaded from http://insar.ca/.

scholarly journals Subglacial hydrological networks in Antarctica and their impact on ice flow

2004 ◽  
Vol 39 ◽  
pp. 67-72 ◽  
Author(s):  
Frédérique Remy ◽  
Benoît Legresy
Keyword(s):  
Remote Sensing ◽  
Ice Flow ◽  
Elevation Data ◽  
Antarctic Continent ◽  
Satellite Radar ◽  
Basal Melting ◽  
The Antarctic ◽  
Satellite Radar Altimetry ◽  
East West ◽  
Geothermal Flux

AbstractDeep beneath the thick ice cover of the Antarctic continent there exist subglacial hydrological networks, within which basal meltwater can flow. In this paper, we use surface elevation data from European Remote-sensing Satellite radar altimetry to map these subglacial hydrological networks for the whole continent. We observe a confused pattern of subglacial systems, linking regions where basal melting takes place. In some regions, channels can be followed over some hundreds of kilometres. Some of these meet the ice-sheet margin, suggesting that meltwater can be transported all the way to the ocean. We observe an east–west gradient in the distribution of hydrological networks that could be explained by the geothermal flux pattern.

scholarly journals Basal melting beneath a fast-flowing temperate tidewater glacier

2013 ◽  
Vol 54 (63) ◽  
pp. 265-271 ◽  
Author(s):  
D.J. Alexander ◽  
T.R.H. Davies ◽  
J. Shulmeister
Keyword(s):  
Mass Balance ◽  
Published Data ◽  
Glacier Mass Balance ◽  
Glacier Surface ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Tidewater Glacier ◽  
Order Of Magnitude ◽  
Basal Melting

AbstractThe role of melting at the base of temperate tidewater glaciers is rarely discussed, and its potential importance for total glacier mass balance and subglacial dynamics is often overlooked. We use Columbia Glacier, Alaska, USA, as an example of a temperate tidewater glacier to estimate the spatial distribution of basal melt due to friction both before and during the glacier’s well-documented retreat since the early 1980s. Published data on glacier surface and bed profiles, ice-flow velocities and surface melt were collated and used as input data for a two-dimensional basal melt model. We estimate that before the retreat of Columbia Glacier (pre-1980s), mean basal melt amounted to 61 mm a–1, increasing to 129 mma–1 during retreat (post-1980s). According to our calculations, basal melt accounts for 3% and 5% of total glacier melt for the pre-retreat and syn-retreat (i.e. during retreat) glacier profiles, respectively. These calculations of basal melt are an order of magnitude greater than those typically reported in polar glacier settings. Basal melting in temperate tidewater settings may be a non-negligible process affecting glacier mass balance and subglacial dynamics.

scholarly journals Retrieving and Verifying Three-Dimensional Surface Motion Displacement of Mountain Glacier from Sentinel-1 Imagery Using Optimized Method

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1793
Author(s):  
Yanqiang Wang ◽  
Jun Zhao ◽  
Zhongqin Li ◽  
Mingjun Zhang ◽  
Yuchun Wang ◽  
...  
Keyword(s):  
Time Series ◽  
Three Dimensional ◽  
Measurement Data ◽  
Surface Velocity ◽  
Special Importance ◽  
Mountain Glacier ◽  
Surface Motion ◽  
Mountain Glaciers ◽  
3D Surface ◽  
Offset Tracking

The time series study of glacier movement is of special importance for rational management of freshwater resources, studying glacier evolution, understanding mechanism of glacier movement, and assessing disasters caused by glacier movement. In this paper, we put forward an optimization scheme for the shortcomings in the calculation method of using remote sensing to invert the three-dimensional (3D) surface motion displacement of glacier. The optimized method consists of Offset Tracking method, Optimizing the offset tracking results by means of iterative filtering, OT-SBAS technology and Conversion of 3D surface motion displacement of glacier. The Urumqi Glacier No. 1 was selected to test the optimized method. The 3D surface motion displacement of Urumqi Glacier No. 1 was retrieved by using the optimized method based on the ascending and descending Sentinel-1 datasets from 19 April to 29 August 2018. The distribution of 3D surface velocity of the Urumqi Glacier No. 1 was obtained in time series, and the accuracy of the inversion results was evaluated by using the field measurement data. The results show that the accuracies of the inverted displacements of east branch of Urumqi Glacier No. 1 (UG1E) were about 0.062, 0.063, and 0.152 m in the east, north and vertical directions, and these values for the west branch (UG1W) were 0.015, 0.020 and 0.026 m, respectively. It is indicated that using Sentinel-1 ascending and descending data and using the optimized method to retrieve the 3D surface motion displacement of glacier should satisfy the requirements of inversing the 3D surface motion displacement of high-latitude mountain glaciers in China.

scholarly journals Brief communication: "Oldest Ice" patches diagnosed 37 km southwest of Dome C, East Antarctica

2018 ◽  
Author(s):  
Olivier Passalacqua ◽  
Marie Cavitte ◽  
Olivier Gagliardini ◽  
Fabien Gillet-Chaulet ◽  
Frédéric Parrenin ◽  
...  
Keyword(s):  
Selection Criteria ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Ice Flow ◽  
Basal Ice ◽  
Drill Site ◽  
Ice Flows ◽  
Basal Melting ◽  
Balance Trade ◽  
Collective Thinking

Abstract. The presence of ice as old as 1.5 Ma is very likely southwest of Dome C, where a bedrock relief high makes the ice thin enough to prevent basal melting. Three-dimensional ice flow modelling is required to ensure that the basal ice is old enough above the bedrock, and that the age resolution of the ice archive is sufficient. A 3D ice flow simulation is led to calculate selection criteria that together locate patches of ice with likely old, well-resolved, undisturbed and datable ice. These patches on the flanks of the bed relief are a balance trade-off between risks of basal melting and sufficient age resolution. The trajectories of the ice particles towards these sites are short and the ice flows over a smoothly undulating bed. Several precise locations of potential 1.5 Ma-old ice are proposed, to nourish the collective thinking on the precise location of a future drill site.

scholarly journals Interaction between ice sheet dynamics and subglacial lake circulation: a coupled modelling approach

2010 ◽  
Vol 4 (1) ◽  
pp. 1-12 ◽  
Author(s):  
M. Thoma ◽  
K. Grosfeld ◽  
C. Mayer ◽  
F. Pattyn
Keyword(s):  
Boundary Conditions ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Eddy Diffusion ◽  
Lake Area ◽  
Ice Flow ◽  
Coupled Modelling ◽  
Ice Sheet Dynamics ◽  
Subglacial Lakes ◽  
Basal Melting

Abstract. Subglacial lakes in Antarctica influence to a large extent the flow of the ice sheet. In this study we use an idealised lake geometry to study this impact. We employ a) an improved three-dimensional full-Stokes ice flow model with a nonlinear rheology, b) a three-dimensional fluid dynamics model with eddy diffusion to simulate the basal mass balance at the lake-ice interface, and c) a newly developed coupler to exchange boundary conditions between the two individual models. Different boundary conditions are applied over grounded ice and floating ice. This results in significantly increased temperatures within the ice on top of the lake, compared to ice at the same depth outside the lake area. Basal melting of the ice sheet increases this lateral temperature gradient. Upstream the ice flow converges towards the lake and accelerates by about 10% whenever basal melting at the ice-lake boundary is present. Above and downstream of the lake, where the ice flow diverges, a velocity decrease of about 10% is simulated.

scholarly journals Interaction between ice sheet dynamics and subglacial lake circulation: a coupled modelling approach

2009 ◽  
Vol 3 (3) ◽  
pp. 805-829 ◽  
Author(s):  
M. Thoma ◽  
K. Grosfeld ◽  
C. Mayer ◽  
F. Pattyn
Keyword(s):  
Boundary Conditions ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Eddy Diffusion ◽  
Lake Area ◽  
Ice Flow ◽  
Coupled Modelling ◽  
Ice Sheet Dynamics ◽  
Subglacial Lakes ◽  
Basal Melting

Abstract. Subglacial lakes in Antarctica influence to a large extent the flow of the ice sheet. In this study we use an idealised lake geometry to study this impact. We employ a) an improved three-dimensional full Stokes ice flow model with a nonlinear rheology, b) a three-dimensional fluid dynamics model with eddy diffusion to simulate basal mass balance, and c) a newly developed coupler to exchange boundary conditions between individual models. Different boundary conditions are applied over grounded ice and floating ice. This results in significantly increased temperatures within the ice on top of the lake, compared to ice at the same depth outside the lake area. Basal melting of the ice sheet increases this lateral temperature gradient. Upstream the ice flow converges towards the lake and accelerates by about 10% whenever basal melting at the ice–lake boundary is present. Above and downstream of the lake, where the ice flow diverges, a velocity decrease of about 10% is simulated.

Defocus ramp correction in spot-scan imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 130-131
Author(s):  
Kenneth H. Downing
Keyword(s):  
Computer Control ◽  
Three Dimensional ◽  
Sufficient Accuracy ◽  
Objective Lens ◽  
Electron Crystallography ◽  
Contrast Transfer Function ◽  
Tilt Axis ◽  
Specimen Height ◽  
The Difference ◽  
Envelope Functions

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.

EVALUASI PROYEKSI DEMAND BARANG DAN PENUMPANG PELABUHAN DI PROVINSI MALUKU

2019 ◽  
Vol 19 (2) ◽  
pp. 101-110
Author(s):  
Adrian Firdaus ◽  
M. Dwi Yoga Sutanto ◽  
Rajin Sihombing ◽  
M. Weldy Hermawan
Keyword(s):  
Time Series ◽  
Projection Method ◽  
Development Plan ◽  
Master Plan ◽  
Port Development ◽  
Loading And Unloading ◽  
The Difference ◽  
Existing Data

Abstract Every port in Indonesia must have a Port Master Plan that contains an integrated port development plan. This study discusses one important aspect in the preparation of the Port Master Plan, namely the projected movement of goods and passengers, which can be used as a reference in determining the need for facilities at each stage of port development. The case study was conducted at a port located in a district in Maluku Province and aims to evaluate the analysis of projected demand for goods and passengers occurring at the port. The projection method used is time series and econometric projection. The projection results are then compared with the existing data in 2018. The results of this study show that the econometric projection gives adequate results in predicting loading and unloading activities as well as the number of passenger arrival and departure in 2018. This is indicated by the difference in the percentage of projection results towards the existing data, which is smaller than 10%. Whereas for loading and unloading activities, time series projections with logarithmic trends give better results than econometric projections. Keywords: port, port master plan, port development, unloading activities  Abstrak Setiap pelabuhan di Indonesia harus memiliki sebuah Rencana Induk Pelabuhan yang memuat rencana pengem-bangan pelabuhan secara terpadu. Studi ini membahas salah satu aspek penting dalam penyusunan Rencana Induk Pelabuhan, yaitu proyeksi pergerakan barang dan penumpang, yang dapat dipakai sebagai acuan dalam penentuan kebutuhan fasilitas di setiap tahap pengembangan pelabuhan. Studi kasus dilakukan pada sebuah pelabuhan yang terletak di sebuah kabupaten di Provinsi Maluku dan bertujuan untuk melakukan evaluasi ter-hadap analisis proyeksi demand barang dan penumpang yang terjadi di pelabuhan tersebut. Metode proyeksi yang dipakai adalah proyeksi deret waktu dan ekonometrik. Hasil proyeksi selanjutnya dibandingkan dengan data eksisting tahun 2018. Hasil studi ini menunjukkan bahwa proyeksi ekonometrik memberikan hasil yang cukup baik dalam memprediksi aktivitas bongkar barang serta jumlah penumpang naik dan turun di tahun 2018. Hal ini diindikasikan dengan selisih persentase hasil proyeksi terhadap data eksisting yang lebih kecil dari 10%. Sedangkan untuk aktivitas muat barang, proyeksi deret waktu dengan tren logaritmik memberikan hasil yang lebih baik daripada proyeksi ekonometrik. Kata-kata kunci: pelabuhan, rencana induk pelabuhan, pengembangan pelauhan, aktivitas bongkar barang

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