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  • PANGAEA  (5)
  • INT GLACIOL SOC  (1)
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  • 1
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    Remotely sensed surface velocities, Lagrangian basal melt rates, terminus positions, grounding lines as well as modelling results of Peterman Glacier (northern Greenland) (2018)
    PANGAEA
    In:  Supplement to: Rückamp, Martin; Neckel, Niklas; Berger, Sophie; Humbert, Angelika; Helm, Veit (2019): Calving Induced Speedup of Petermann Glacier. Journal of Geophysical Research-Earth Surface, https://doi.org/10.1029/2018JF004775
    Details
    Publication Date: 2023-03-16
    Description: This study assesses the response on ice dynamics of Petermann Glacier, a major outlet glacier in northern Greenland, to the 2012 and a possible future calving event. So far Petermann Glacier has been believed to be dynamically stable as another large calving event in 2010 had no significant impact on flow velocity or grounding line retreat. By analyzing a time series of remotely sensed surface velocities, we find an average acceleration of 10% between winter 2011/2012 and winter 2016/2017. This increase in surface velocity is not linear but can be separated into two parts, starting in 2012 and 2016 respectively. By conducting modelling experiments, we show that the first speed-up can be directly connected to the 2012 calving event, while the second speed-up is not captured. However, on recent remote sensing imagery newly developing fractures are clearly visible ~12,km upstream from the terminus, propagating from the eastern fjord wall to the center of the ice tongue, indicating a possible future calving event. By including these fracture zones as a new terminus position in the modelling domain we are able to reproduce the second speed-up, suggesting that surface velocities remain on the 2016/2017 level after the anticipated calving event. This indicates that, from a dynamical point of view, the terminus region has already detached from the main ice tongue.
    Keywords: AWI_Glac; File format; File name; File size; Glaciology @ AWI; North Greenland; Petermann_Glacier; RADAR; Radar profile; Uniform resource locator/link to file
    Type: Dataset
    Format: text/tab-separated-values, 72 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 2
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    Modelling calving front dynamics using a level-set method: application to Jakobshavn Isbræ, West Greenland, links model results in MATLAB format (2016)
    PANGAEA
    In:  Supplement to: Bondzio, Johannes H; Seroussi, Hélène; Morlighem, Mathieu; Kleiner, Thomas; Rückamp, Martin; Humbert, Angelika; Larour, Eric Y (2016): Modelling calving front dynamics using a level-set method: application to Jakobshavn Isbræ, West Greenland. The Cryosphere, 10(2), 497-510, https://doi.org/10.5194/tc-10-497-2016
    Details
    Publication Date: 2023-01-13
    Description: Calving is a major mechanism of ice discharge of the Antarctic and Greenland ice sheets, and a change in calving front position affects the entire stress regime of marine terminating glaciers. The representation of calving front dynamics in a 2-D or 3-D ice sheet model remains non-trivial. Here, we present the theoretical and technical framework for a level-set method, an implicit boundary tracking scheme, which we implement into the Ice Sheet System Model (ISSM). This scheme allows us to study the dynamic response of a drainage basin to user-defined calving rates. We apply the method to Jakobshavn Isbræ, a major marine terminating outlet glacier of the West Greenland Ice Sheet. The model robustly reproduces the high sensitivity of the glacier to calving, and we find that enhanced calving triggers significant acceleration of the ice stream. Upstream acceleration is sustained through a combination of mechanisms. However, both lateral stress and ice influx stabilize the ice stream. This study provides new insights into the ongoing changes occurring at Jakobshavn Isbræ and emphasizes that the incorporation of moving boundaries and dynamic lateral effects, not captured in flow-line models, is key for realistic model projections of sea level rise on centennial timescales.
    Keywords: Jakobshavn_Isbræ_drainage_basin; West Greenland
    Type: Dataset
    Format: application/zip, 469.2 MBytes
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 3
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    Present-day King George Island ice cap geometry measured by ground penetrating radar in 2008/09 (2011)
    PANGAEA
    In:  Supplement to: Rückamp, Martin; Blindow, Norbert (2011): King George Island ice cap geometry updated with airborne GPR measurements. Earth System Science Data, 4(1), 23-30, https://doi.org/10.5194/essd-4-23-2012
    Details
    Publication Date: 2023-10-28
    Description: We present a consistent data set for the ice thickness, the bedrock topography and the ice surface topography of the King George Island ice cap (Arctowski Icefield and the adjacent central part). The data set is composed of groundbased and airborne Ground Penetrating Radar (GPR) and differential GPS (DGPS) measurements, obtained during several field campaigns. The data set incorporates groundbased measurements in the safely accessible inner parts and airborne measurements in the heavily crevassed coastal areas of the ice cap. In particular, the inclusion of airborne GPR measurements with the 30MHz BGR-P30-System developed at the Institute of Geophysics (University of Münster) completes the picture of the ice geometry substantially. The compiled digital elevation model of the bedrock shows a rough, highly variable topography with pronounced valleys, ridges, and troughs. The mean ice thickness is approx. 238m, with a maximum value of approx. 400m in the surveyed area. Noticeable are bounded areas in the bedrock topography below sea level where marine based ice exists.
    Keywords: ELEVATION; Elevation 2; Ground-penetrating radar (GPR); Ice thickness, glacier; King_George_Island; King George Island, Antarctic Peninsula; LATITUDE; LONGITUDE; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; SPP1158; UTM Easting, Universal Transverse Mercator; UTM Northing, Universal Transverse Mercator; UTM Zone, Universal Transverse Mercator
    Type: Dataset
    Format: text/tab-separated-values, 960475 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 4
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    Mass balance measurements on King George Island ice cap in 2007 and 2008 (2011)
    PANGAEA
    In:  Supplement to: Rückamp, Martin; Braun, Matthias Holger; Suckro, Sonja K; Blindow, Norbert (2011): Observed glacial changes on the King George Island ice cap, Antarctica, in the last decade. Global and Planetary Change, 79(1-2), 99-109, https://doi.org/10.1016/j.gloplacha.2011.06.009
    Details
    Publication Date: 2023-10-28
    Description: The Antarctic Peninsula has been identified as a region of rapid on-going climate change with impacts on the cryosphere. The knowledge of glacial changes and freshwater budgets resulting from intensified glacier melt is an important boundary condition for many biological and integrated earth system science approaches. We provide a case study on glacier and mass balance changes for the ice cap of King George Island. The area loss between 2000 and 2008 amounted to about 20 km**2 (about 1.6% of the island area) and compares to glacier retreat rates observed in previous years. Measured net accumulation rates for two years (2007 and 2008) show a strong interannual variability with maximum net accumulation rates of 4950 mm w.e./a and 3184 mm w.e./a, respectively. These net accumulation rates are at least 4 times higher than reported mean values (1926-95) from an ice core. An elevation dependent precipitation rate of 343 mm w.e./a (2007) and 432 mm w.e./a (2008) per 100 m elevation increase was observed. Despite these rather high net accumulation rates on the main ice cap, consistent surface lowering was observed at elevations below 270 m above ellipsoid over an 11-year period. These DGPS records reveal a linear dependence of surface lowering with altitude with a maximum annual surface lowering rate of 1.44 m/a at 40 m and -0.20 m/a at 270 m above ellipsoid. These results fit well to observations by other authors and surface lowering rates derived from the ICESat laser altimeter. Assuming that climate conditions of the past 11 years continue, the small ice cap of Bellingshausen Dome will disappear in about 285 years.
    Keywords: DATE/TIME; ELEVATION; King_George_Island; King George Island, Antarctic Peninsula; LATITUDE; LONGITUDE; Mass balance in water equivalent per year; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; SPP1158; UTM Easting, Universal Transverse Mercator; UTM Northing, Universal Transverse Mercator; UTM Zone, Universal Transverse Mercator
    Type: Dataset
    Format: text/tab-separated-values, 124 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 5
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    Measured ice surface velocities on the King George Island ice cap with DGPS (2012)
    PANGAEA
    In:  Supplement to: Rückamp, Martin; Blindow, Norbert; Suckro, Sonja K; Braun, Matthias Holger; Humbert, Angelika (2010): Dynamics of the ice cap on King George Island, Antarctica: field measurements and numerical simulations. Annals of Glaciology, 51(55), 80-90, https://doi.org/10.3189/172756410791392817
    Details
    Publication Date: 2023-10-28
    Description: King George Island is located at the northern tip of the Antarctic Peninsula, which is influenced by maritime climate conditions. The observed mean annual air temperature at sea level is -2.4°C. Thus, the ice cap is regarded as sensitive to changing climatic conditions. Ground-penetrating radar surveys indicate a partly temperate ice cap with an extended water layer at the firn/ice transition of the up to 700 m high ice cap. Measured firn temperatures are close to 0°C at the higher elevations, and they differ considerably from the measured mean annual air temperature. The aim of this paper is to present ice-flow dynamics by means of observations and simulations of the flow velocities. During several field campaigns from 1997/98 to 2008/09, ice surface velocities were derived with repeated differential GPS measurements. Ice velocities vary from 0.7 m/a at the dome to 112.1 m/a along steep slopes. For the western part of the ice cap a three-dimensional diagnostic full-Stokes model was applied to calculate ice flow. Parameters of the numerical model were identified with respect to measured ice surface velocities. The simulations indicate cold ice at higher elevations, while temperate ice at lower elevations is consistent with the observations.
    Keywords: ELEVATION; Ice-flow direction; King_George_Island; King George Island, Antarctic Peninsula; LATITUDE; LONGITUDE; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; SPP1158; UTM Easting, Universal Transverse Mercator; UTM Northing, Universal Transverse Mercator; UTM Zone, Universal Transverse Mercator; Velocity magnitude
    Type: Dataset
    Format: text/tab-separated-values, 610 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 6
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    Grounding-line migration in plan-view marine ice-sheet models: results of the ice2sea MISMIP3d intercomparison (2013)
    INT GLACIOL SOC
    In:  EPIC3Journal of Glaciology, INT GLACIOL SOC, 59(215), pp. 410-422, ISSN: 0022-1430
    Details
    Publication Date: 2019-07-17
    Description: Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (〈500m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of 〈5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Limitation Availability
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    PAPER (OA)
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