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  • 1
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    Online Resource
    Response of the flow dynamics of Bowdoin Glacier, northwestern Greenland, to basal lubrication and tidal forcing
    Cambridge University Press (CUP) ; 2019
    In:  Journal of Glaciology Vol. 65, No. 250 ( 2019-04), p. 225-238
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 65, No. 250 ( 2019-04), p. 225-238
    Abstract: We use the full-Stokes model Elmer/Ice to investigate the present dynamics of Bowdoin Glacier, a marine-terminating outlet glacier in northwestern Greenland. Short-term speed variations of the glacier were observed, correlating with air temperature and precipitation, and with the semi-diurnal ocean tides. We use a control inverse method to determine the distribution of basal friction. This reveals that most of the glacier area is characterized by near-plug-flow conditions, while some sticky spots are also identified. We then conduct experiments to test the sensitivity of the glacier flow to basal lubrication and tidal forcing at the calving front. Reduction of the basal drag by 10–40% produces speed-ups that agree approximately with the observed range of speed-ups that result from warm weather and precipitation events. In agreement with the observations, tidal forcing and surface speed near the calving front are found to be in anti-phase (high tide corresponds to low speed, and vice versa). However, the amplitude of the semi-diurnal variability is underpredicted by a factor ~ 3, which is likely related to either inaccuracies in the surface and bedrock topographies or mechanical weakening due to crevassing.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2018.106
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2140541-4
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  • 2
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    Future projections for the Antarctic ice sheet until the year 2300 with a climate-index method
    Cambridge University Press (CUP) ; 2023
    In:  Journal of Glaciology
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP)
    Abstract: As part of the Coupled Model Intercomparison Project Phase 6 (CMIP6), the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) was devised to assess the likely sea-level-rise contribution from the Earth's ice sheets. Here, we construct an ensemble of climate forcings for Antarctica until the year 2300 based on original ISMIP6 forcings until 2100, combined with climate indices from simulations with the MIROC4m climate model until 2300. We then use these forcings to run simulations for the Antarctic ice sheet with the SICOPOLIS model. For the unabated warming pathway RCP8.5/SSP5-8.5, the ice sheet suffers a severe mass loss, amounting to ~ 1.5 m SLE (sea-level equivalent) for the fourteen-experiment mean, and ~ 3.3 m SLE for the most sensitive experiment. Most of this loss originates from West Antarctica. For the reduced emissions pathway RCP2.6/SSP1-2.6, the loss is limited to a three-experiment mean of ~ 0.16 m SLE. The means are approximately two times larger than what was found in a previous study (Chambers and others, 2022, doi:10.1017/jog.2021.124) that assumed a sustained late-21st-century climate beyond 2100, demonstrating the importance of post-2100 climate trends on Antarctic mass changes in the 22nd and 23rd centuries.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2023.41
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2140541-4
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  • 3
    Online Resource
    Online Resource
    Large-scale ice-sheet modelling as a means of dating deep ice cores in Greenland
    Cambridge University Press (CUP) ; 1997
    In:  Journal of Glaciology Vol. 43, No. 144 ( 1997), p. 307-310
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 43, No. 144 ( 1997), p. 307-310
    Abstract: The three-dimensional ice-sheet model SICOPOLIS is used to simulate the dynamic/thermody namic behaviour of the entire Greenland ice sheet from 250 000 a BP until today. External forcing consists of a surface-temperature history constructed from δ 18 O data of the GRIP core, a snowfall history coupled linearly to that of the surface temperature, a piecewise linear sea-level scenario and a constant geothermal heat flux. The simulated Greenland ice sheet is investigated in the vicinity of Summit, the position where the maximum elevation is taken, and where the two drill sites GRIP and GISP2 are situated 28km apart from each other. In this region, the agreement between modelled and observed topography and ice temperature turns out to be very good. Computed age-depth profiles for GRIP and GISP2 are presented, which can he used to complete the dating of these cores in the deeper regions where annual-layer counting is not possible. However, artificial diffusion influences the computed ages in a near-basal boundary layer of approximately 15% of the ice thickness, so that the age at the bottom of the cores cannot be predicted yet.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/S0022143000003257
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1997
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  • 4
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    Online Resource
    Antarctic ice sheet response to sudden and sustained ice-shelf collapse (ABUMIP)
    Cambridge University Press (CUP) ; 2020
    In:  Journal of Glaciology Vol. 66, No. 260 ( 2020-12), p. 891-904
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 66, No. 260 ( 2020-12), p. 891-904
    Abstract: Antarctica's ice shelves modulate the grounded ice flow, and weakening of ice shelves due to climate forcing will decrease their ‘buttressing’ effect, causing a response in the grounded ice. While the processes governing ice-shelf weakening are complex, uncertainties in the response of the grounded ice sheet are also difficult to assess. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) compares ice-sheet model responses to decrease in buttressing by investigating the ‘end-member’ scenario of total and sustained loss of ice shelves. Although unrealistic, this scenario enables gauging the sensitivity of an ensemble of 15 ice-sheet models to a total loss of buttressing, hence exhibiting the full potential of marine ice-sheet instability. All models predict that this scenario leads to multi-metre (1–12 m) sea-level rise over 500 years from present day. West Antarctic ice sheet collapse alone leads to a 1.91–5.08 m sea-level rise due to the marine ice-sheet instability. Mass loss rates are a strong function of the sliding/friction law, with plastic laws cause a further destabilization of the Aurora and Wilkes Subglacial Basins, East Antarctica. Improvements to marine ice-sheet models have greatly reduced variability between modelled ice-sheet responses to extreme ice-shelf loss, e.g. compared to the SeaRISE assessments.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2020.67
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 2140541-4
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  • 5
    Online Resource
    Online Resource
    Mass loss of the Antarctic ice sheet until the year 3000 under a sustained late-21st-century climate
    Cambridge University Press (CUP) ; 2022
    In:  Journal of Glaciology Vol. 68, No. 269 ( 2022-06), p. 605-617
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 68, No. 269 ( 2022-06), p. 605-617
    Abstract: Ice-sheet simulations of Antarctica extending to the year 3000 are analysed to investigate the long-term impacts of 21st-century warming. Climate projections are used as forcing until 2100 and afterwards no climate trend is applied. Fourteen experiments are for the ‘unabated warming’ pathway, and three are for the ‘reduced emissions’ pathway. For the unabated warming path simulations, West Antarctica suffers a much more severe ice loss than East Antarctica. In these cases, the mass loss amounts to an ensemble average of ~3.5 m sea-level equivalent (SLE) by the year 3000 and ~5.3 m for the most sensitive experiment. Four phases of mass loss occur during the collapse of the West Antarctic ice sheet. For the reduced emissions pathway, the mean mass loss is ~0.24 m SLE. By demonstrating that the consequences of the 21st century unabated warming path forcing are large and long term, the results present a different perspective to ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6). Extended ABUMIP (Antarctic BUttressing Model Intercomparison Project) simulations, assuming sudden and sustained ice-shelf collapse, with and without bedrock rebound, corroborate a negative feedback for ice loss found in previous studies, where bedrock rebound acts to slow the rate of ice loss.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2021.124
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2140541-4
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  • 6
    Online Resource
    Online Resource
    Two-dimensional similarity solutions for finite-mass granular avalanches with coulomb- and viscous-type frictional resistance
    Cambridge University Press (CUP) ; 1993
    In:  Journal of Glaciology Vol. 39, No. 132 ( 1993), p. 357-372
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 39, No. 132 ( 1993), p. 357-372
    Abstract: This paper is concerned with the motion of an unconfined finite mass of granular material down an inclined plane when released from a rest position in the shape of a circular or elliptical paraboloid. The granular mass is treated as a frictional Coulomb-like continuum with a constant angle of internal friction. The basal friction force is assumed to be composed of a Coulomb-type component with a bed-friction angle that is position-dependent and a viscous Voellmy-type resistive stress that is proportional to the velocity squared. The model equations are those of Hutter and others (in press b) and form a spatially two-dimensional set for the evolution of the avalanche height and the depth averaged in-plane velocity components; they hold for a motion of a granular mass along a plane surface. Similarity solutions, i.e. solutions which preserve the shape and the structure of the velocity field, are constructed by decomposing the motion into that of the centre of mass and the deformation relative to it. This decomposition is possible provided the effect of the Voellmy drag on the deformation is ignored. With it, the depth and velocities relative to those of the centre of mass of the moving pile can be determined analytically. It is shown that the pile has a parabolic cap shape and contour lines are elliptical. The semi-axes and the position and velocity of the centre of mass are calculated numerically. We explicitly show that (i) For two-dimensional spreading, a rigid-body motion does not exist, no matter what be the values of the bed-friction angle and the coefficient of viscous drag. (ii) A steady final velocity of the centre of the mass cannot be assumed, but the motion of the centre of mass depends strongly on the value of the Voellmy coefficient. (iii) The geometry of the moving pile depends on the variation of the bed-friction angle with position, as well as on the value of the coefficient of viscous drag.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/S0022143000016026
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1993
    detail.hit.zdb_id: 2140541-4
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  • 7
    Online Resource
    Online Resource
    Mass loss of the Greenland ice sheet until the year 3000 under a sustained late-21st-century climate
    Cambridge University Press (CUP) ; 2022
    In:  Journal of Glaciology Vol. 68, No. 269 ( 2022-06), p. 618-624
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 68, No. 269 ( 2022-06), p. 618-624
    Abstract: We conduct extended versions of the ISMIP6 future climate experiments for the Greenland ice sheet until the year 3000 with the model SICOPOLIS. Beyond 2100, the climate forcing is kept fixed at late-21st-century conditions. For the unabated warming pathway RCP8.5/SSP5-8.5, the ice sheet suffers a severe mass loss, which amounts to ~ 1.8 m SLE (sea-level equivalent) for the 12-experiment mean, and ~ 3.5 m SLE (~ 50% of the entire mass) for the most sensitive experiment. For the reduced emissions pathway RCP2.6/SSP1-2.6, the mass loss is limited to a two-experiment mean of ~ 0.28 m SLE. Climate-change mitigation during the next decades will therefore be an efficient means for limiting the contribution of the Greenland ice sheet to sea-level rise in the long term.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2022.9
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2140541-4
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  • 8
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    Online Resource
    Constraining the geothermal heat flux in Greenland at regions of radar-detected basal water
    Cambridge University Press (CUP) ; 2019
    In:  Journal of Glaciology Vol. 65, No. 254 ( 2019-12), p. 1023-1034
    Details
    In: Journal of Glaciology, Cambridge University Press (CUP), Vol. 65, No. 254 ( 2019-12), p. 1023-1034
    Abstract: The spatial distribution of basal water critically impacts the evolution of ice sheets. Current estimates of basal water distribution beneath the Greenland Ice Sheet (GrIS) contain large uncertainties due to poorly constrained boundary conditions, primarily from geothermal heat flux (GHF). The existing GHF models often contradict each other and implementing them in numerical ice-sheet models cannot reproduce the measured temperatures at ice core locations. Here we utilize two datasets of radar-detected basal water in Greenland to constrain the GHF at regions with a thawed bed. Using the three-dimensional ice-sheet model SICOPOLIS, we iteratively adjust the GHF to find the minimum GHF required to reach the bed to the pressure melting point, GHF pmp , at locations of radar-detected basal water. We identify parts of the central-east, south and northwest Greenland with significantly high GHF pmp . Conversely, we find that the majority of low-elevation regions of west Greenland and parts of northeast have very low GHF pmp . We compare the estimated constraints with the available GHF models for Greenland and show that GHF models often do not honor the estimated constraints. Our results highlight the need for community effort to reconcile the discrepancies between radar data, GHF models, and ice core information.
    Type of Medium: Online Resource
    ISSN: 0022-1430 , 1727-5652
    URL: Article
    DOI: 10.1017/jog.2019.79
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2140541-4
    SSG: 14
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