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  • 1
    Online Resource
    Online Resource
    Calving Induced Speedup of Petermann Glacier
    American Geophysical Union (AGU) ; 2019
    In:  Journal of Geophysical Research: Earth Surface Vol. 124, No. 1 ( 2019-01), p. 216-228
    Details
    In: Journal of Geophysical Research: Earth Surface, American Geophysical Union (AGU), Vol. 124, No. 1 ( 2019-01), p. 216-228
    Abstract: Based on remote sensing data, Petermann Glacier sped up after the calving event in 2012 Speedup is caused by a reduction in buttressing Further retreat into the fjord likely causes glacier acceleration
    Type of Medium: Online Resource
    ISSN: 2169-9003 , 2169-9011
    URL: Article
    DOI: 10.1029/2018JF004775
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2019
    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2138320-0
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    Greenland Mass Trends From Airborne and Satellite Altimetry During 2011–2020
    American Geophysical Union (AGU) ; 2022
    In:  Journal of Geophysical Research: Earth Surface Vol. 127, No. 4 ( 2022-04)
    Details
    In: Journal of Geophysical Research: Earth Surface, American Geophysical Union (AGU), Vol. 127, No. 4 ( 2022-04)
    Abstract: The Greenland Ice Sheet contributed 6.9 ± 0.4 mm to sea‐level from April 2011 to April 2020 Satellite altimetry suggests a peak annual ice loss of 498 ± 45 Gt from April 2019 to April 2020 The terminus of Jakobshavn Isbræ is once again dynamically thinning, following a period of dynamic thickening during 2016–2018
    Type of Medium: Online Resource
    ISSN: 2169-9003 , 2169-9011
    URL: Article
    DOI: 10.1029/2021JF006505
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 3094104-0
    detail.hit.zdb_id: 2130824-X
    detail.hit.zdb_id: 2138320-0
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Arctic observations and sustainable development goals – Contributions and examples from ERA-PLANET iCUPE data
    Elsevier BV ; 2022
    In:  Environmental Science & Policy Vol. 132 ( 2022-06), p. 323-336
    Details
    In: Environmental Science & Policy, Elsevier BV, Vol. 132 ( 2022-06), p. 323-336
    Type of Medium: Online Resource
    ISSN: 1462-9011
    URL: Article
    DOI: 10.1016/j.envsci.2022.02.034
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 2026857-9
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  • 4
    Online Resource
    Online Resource
    Analysis of Calving Events in Antarctic Ice Shelves Using Configurational Forces
    Wiley ; 2012
    In:  PAMM Vol. 12, No. 1 ( 2012-12), p. 155-156
    Details
    In: PAMM, Wiley, Vol. 12, No. 1 ( 2012-12), p. 155-156
    Abstract: Previous studies on the sensitivity of cracks in ice shelves with different boundary conditions, stress states and density profiles revealed the need for further analyses. As the transfer of boundary conditions from dynamic ice flow simulations to the linear elastic fracture analyses proved to be a critical point in previous studies, a new approach to relate viscous and elastic material behaviour is proposed. The numerical simulations are conducted using Finite Elements utilizing the concept of configurational forces. To show the applicability of the approach, a 2‐dimensional plane stress geometry with volume loads due to the ice shelf flow is analyzed. The resulting crack path is compared to available crack paths from satellite images. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v12.1
    DOI: 10.1002/pamm.201210068
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2078931-2
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  • 5
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    Online Resource
    A phase field model for fractures in ice shelves
    Wiley ; 2023
    In:  PAMM Vol. 22, No. 1 ( 2023-03)
    Details
    In: PAMM, Wiley, Vol. 22, No. 1 ( 2023-03)
    Abstract: Ice shelves are large floating ice masses, that are formed when glaciers are becoming afloat at the margin of ice sheets. One dominating mass loss mechanism of ice shelves is calving, describing the detachment of icebergs at the front. Ice shelves stabilize inland ice glaciers due to buttressing. If the stabilizing effect of an ice shelf vanishes because of disintegration or thinning, the corresponding glacier accelerates resulting in sea level rise. To describe calving and disintegration of ice shelves, it is important to investigate fracture propagation in ice. A powerful method in fracture mechanics is the phase field method which is based on Griffith's theory. It approximates cracks in a diffuse manner by using a continuous scalar field. We propose a phase field fracture model for ice considering its characteristic material properties. The material behavior of ice depends on the considered time scales. On short time scales it behaves like a solid and while it acts like a fluid on long time scales, which classifies it as a viscoelastic material of Maxwell type. This has been verified by observations. The phase field method allows us to simulate typical fracture situations of ice shelves in Antarctica and Greenland.
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v22.1
    DOI: 10.1002/pamm.202200256
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2078931-2
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  • 6
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    Online Resource
    The First Stage of Firn Densification ‐ An Evaluation of Grain Boundary Sliding
    Wiley ; 2021
    In:  PAMM Vol. 21, No. 1 ( 2021-12)
    Details
    In: PAMM, Wiley, Vol. 21, No. 1 ( 2021-12)
    Abstract: Firn describes the interstage product between snow and ice in cold regions of the earth, where annual snow fall exceeds the amount of snow melting. The continuing accumulation of snow leads to its densificiation due to overburden stress until it becomes ice. In the field of glaciology various attempts on simulating firn densification have been made and new models are still developed, as the knowledge of the firn column's density structure allows important derivations. The presented study reassesses a model description for low density firn based on the process of grain boundary sliding presented by Alley in 1987 [1] using an optimisation approach. By comparing simulation results to 159 measured firn density profiles from Greenland and Antarctica it finds a possible additional dependency of the constitutive relation on the mean surface mass balance. This result is interpreted as an insufficient description of the stress regime.
    Type of Medium: Online Resource
    ISSN: 1617-7061 , 1617-7061
    URL: Issue
    URL: Article
    DOI: 10.1002/pamm.v21.1
    DOI: 10.1002/pamm.202100125
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2078931-2
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  • 7
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    Online Resource
    ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century
    Copernicus GmbH ; 2020
    In:  The Cryosphere Vol. 14, No. 9 ( 2020-09-17), p. 3033-3070
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 9 ( 2020-09-17), p. 3033-3070
    Abstract: Abstract. Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and assess the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimates of the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes, forcings employed and initial states of ice sheet models. This study presents results from ice flow model simulations from 13 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015–2100 as part of the Ice Sheet Model Intercomparison for CMIP6 (ISMIP6). They are forced with outputs from a subset of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), representative of the spread in climate model results. Simulations of the Antarctic ice sheet contribution to sea level rise in response to increased warming during this period varies between −7.8 and 30.0 cm of sea level equivalent (SLE) under Representative Concentration Pathway (RCP) 8.5 scenario forcing. These numbers are relative to a control experiment with constant climate conditions and should therefore be added to the mass loss contribution under climate conditions similar to present-day conditions over the same period. The simulated evolution of the West Antarctic ice sheet varies widely among models, with an overall mass loss, up to 18.0 cm SLE, in response to changes in oceanic conditions. East Antarctica mass change varies between −6.1 and 8.3 cm SLE in the simulations, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional simulated mass loss of 28 mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the climate forcing, the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 climate models show an additional mass loss of 0 and 3 cm of SLE on average compared to simulations done under present-day conditions for the two CMIP5 forcings used and display limited mass gain in East Antarctica.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-14-3033-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2393169-3
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  • 8
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    Online Resource
    The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6
    Copernicus GmbH ; 2020
    In:  The Cryosphere Vol. 14, No. 9 ( 2020-09-17), p. 3071-3096
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 14, No. 9 ( 2020-09-17), p. 3071-3096
    Abstract: Abstract. The Greenland ice sheet is one of the largest contributors to global mean sea-level rise today and is expected to continue to lose mass as the Arctic continues to warm. The two predominant mass loss mechanisms are increased surface meltwater run-off and mass loss associated with the retreat of marine-terminating outlet glaciers. In this paper we use a large ensemble of Greenland ice sheet models forced by output from a representative subset of the Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The simulations are part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate the sea-level contribution together with uncertainties due to future climate forcing, ice sheet model formulations and ocean forcing for the two greenhouse gas concentration scenarios RCP8.5 and RCP2.6. The results indicate that the Greenland ice sheet will continue to lose mass in both scenarios until 2100, with contributions of 90±50 and 32±17 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largest mass loss is expected from the south-west of Greenland, which is governed by surface mass balance changes, continuing what is already observed today. Because the contributions are calculated against an unforced control experiment, these numbers do not include any committed mass loss, i.e. mass loss that would occur over the coming century if the climate forcing remained constant. Under RCP8.5 forcing, ice sheet model uncertainty explains an ensemble spread of 40 mm, while climate model uncertainty and ocean forcing uncertainty account for a spread of 36 and 19 mm, respectively. Apart from those formally derived uncertainty ranges, the largest gap in our knowledge is about the physical understanding and implementation of the calving process, i.e. the interaction of the ice sheet with the ocean.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    URL: Article
    DOI: 10.5194/tc-14-3071-2020
    DOI: 10.5194/tc-14-3071-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2393169-3
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  • 9
    Online Resource
    Online Resource
    Polarimetric radar reveals the spatial distribution of ice fabric at domes and divides in East Antarctica
    Copernicus GmbH ; 2022
    In:  The Cryosphere Vol. 16, No. 5 ( 2022-05-06), p. 1719-1739
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 16, No. 5 ( 2022-05-06), p. 1719-1739
    Abstract: Abstract. Ice crystals are mechanically and dielectrically anisotropic. They progressively align under cumulative deformation, forming an ice-crystal-orientation fabric that, in turn, impacts ice deformation. However, almost all the observations of ice fabric are from ice core analysis, and its influence on the ice flow is unclear. Here, we present a non-linear inverse approach to process co- and cross-polarized phase-sensitive radar data. We estimate the continuous depth profile of georeferenced ice fabric orientation along with the reflection ratio and horizontal anisotropy of the ice column. Our method approximates the complete second-order orientation tensor and all the ice fabric eigenvalues. As a result, we infer the vertical ice fabric anisotropy, which is an essential factor to better understand ice deformation using anisotropic ice flow models. The approach is validated at two Antarctic ice core sites (EPICA (European Project for Ice Coring in Antarctica) Dome C and EPICA Dronning Maud Land) in contrasting flow regimes. Spatial variability in ice fabric characteristics in the dome-to-flank transition near Dome C is quantified with 20 more sites located along with a 36 km long cross-section. Local horizontal anisotropy increases under the dome summit and decreases away from the dome summit. We suggest that this is a consequence of the non-linear rheology of ice, also known as the Raymond effect. On larger spatial scales, horizontal anisotropy increases with increasing distance from the dome. At most of the sites, the main driver of ice fabric evolution is vertical compression, yet our data show that the horizontal distribution of the ice fabric is consistent with the present horizontal flow. This method uses polarimetric-radar data, which are suitable for profiling radar applications and are able to constrain ice fabric distribution on a spatial scale comparable to ice flow observations and models.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-16-1719-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2393169-3
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  • 10
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    Online Resource
    On the evolution of an ice shelf melt channel at the base of Filchner Ice Shelf, from observations and viscoelastic modeling
    Copernicus GmbH ; 2022
    In:  The Cryosphere Vol. 16, No. 10 ( 2022-10-10), p. 4107-4139
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 16, No. 10 ( 2022-10-10), p. 4107-4139
    Abstract: Abstract. Ice shelves play a key role in the stability of the Antarctic Ice Sheet due to their buttressing effect. A loss of buttressing as a result of increased basal melting or ice shelf disintegration will lead to increased ice discharge. Some ice shelves exhibit channels at the base that are not yet fully understood. In this study, we present in situ melt rates of a channel which is up to 330 m high and located in the southern Filchner Ice Shelf. Maximum observed melt rates are 2 m yr−1. Melt rates inside the channel decrease in the direction of ice flow and turn to freezing ∼55 km downstream of the grounding line. While closer to the grounding line melt rates are higher within the channel than outside, this relationship reverses further downstream. Comparing the modeled evolution of this channel under present-day climate conditions over 250 years with its present geometry reveals a mismatch. Melt rates twice as large as the present-day values are required to fit the observed geometry. In contrast, forcing the model with present-day melt rates results in a closure of the channel, which contradicts observations. The ice shelf experiences strong tidal variability in vertical strain rates at the measured site, and discrete pulses of increased melting occurred throughout the measurement period. The type of melt channel in this study diminishes in height with distance from the grounding line and is hence not a destabilizing factor for ice shelves.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-16-4107-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2393169-3
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