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  • 1
    Online Resource
    Online Resource
    Berlin, Heidelberg :Springer Berlin / Heidelberg,
    Keywords: Glaciers. ; Ice sheets. ; Gletscher--Kontinuumsmechanik--Numerisches Modell. ; Glaciers. ram. ; Fluides, Dynamique des. ram. ; Inlandsis. ram. ; Gletscher. swd. ; Kontinuumsmechanik. swd. ; Numerisches Modell. swd. ; Electronic books.
    Description / Table of Contents: Based on general continuum mechanics, the different initial-boundary-value problems for the flow of ice sheets, ice shelves, ice caps and glaciers are systematically derived. Emphasis is put on developing approximation hierarchies for the different systems.
    Type of Medium: Online Resource
    Pages: 1 online resource (296 pages)
    Edition: 1st ed.
    ISBN: 9783642034152
    Series Statement: Advances in Geophysical and Environmental Mechanics and Mathematics Series
    DDC: 551.31
    Language: English
    Note: Intro -- Preface -- Acknowledgements -- Contents -- Ice in the Climate System -- The Terrestrial Cryosphere -- Land Ice on the Present-Day Earth -- An Excursion into the Past -- Ice Sheets, Glaciers and Global Warming -- Vectors, Tensors and Their Representation -- Definition of a Vector, Basic Properties -- Representation of Vectors as Number Triples -- Tensors of Order 2 -- Higher Order Tensors -- Vector and Tensor Analysis -- Elements of Continuum Mechanics -- Bodies and Configurations -- Kinematics -- Deformation Gradient, Stretch Tensors -- Velocity, Acceleration, Velocity Gradient -- Balance Equations -- Reynolds' Transport Theorem -- General Balance Equation -- General Jump Condition -- Mass Balance -- Momentum Balance -- Balance of Angular Momentum -- Energy Balance -- Constitutive Equations -- Homogeneous Viscous Thermoelastic Bodies -- Linear Elastic Solid -- Newtonian Fluid -- Constitutive Equations for Polycrystalline Ice -- Microstructure of Ice -- Creep of Polycrystalline Ice -- Flow Relation -- Glen's Flow Law -- Regularised Glen's Flow Law -- Smith-Morland Flow Law -- Flow Enhancement Factor -- Heat Flux and Internal Energy -- Elasticity -- Large-Scale Dynamics of Ice Sheets -- Full Stokes Flow Problem -- Field Equations -- Boundary Conditions -- Ice Thickness Equation -- Hydrostatic Approximation -- First Order Approximation -- Shallow Ice Approximation -- Driving Stress -- Analytical Solutions -- Simplified Problem -- Vialov Profile -- Bueler Profile -- Numerical Methods -- Terrain-Following Coordinate Transformation -- Plane Strain Shallow Ice Equations -- Discretised Ice Sheet Equations -- Example: The EGIG Line of the Greenland Ice Sheet -- Large-Scale Dynamics of Ice Shelves -- Full Stokes Flow Problem -- Field Equations, Boundary Conditions at the Free Surface -- Boundary Conditions at the Ice Base. , Boundary Conditions at the Grounding Line and Calving Front -- Hydrostatic Approximation -- Shallow Shelf Approximation -- Ice Shelf Ramp -- Numerical Methods -- Mechanical Ice Shelf Problem -- Weak Formulation -- Discretisation of the Ice Shelf Domain -- Galerkin Finite Element Method -- Iteration -- Example: The Ross Ice Shelf -- Dynamics of Glacier Flow -- Glaciers Versus Ice Sheets -- Parallel Sided Slab -- Scaling Arguments and Hierarchy of Approximations -- First Order Plane Strain Approximation -- Basal Sliding -- General Remarks -- Mean Sliding over Rough Hard Beds -- Soft Beds on Sediment Layers -- Numerical Methods for the Stress and Velocity Fields -- Method of Lines -- Global Discretisation Schemes -- Vertical Velocity Component -- Trajectories -- Transverse First Order Flow Profiles -- Applications and Limitations of Glacier Models -- Information on Glaciers -- Inverse Problems -- The Shallowness of Glaciers -- Discontinuities -- Glacial Isostasy -- Background -- Structure of the Earth -- Simple Isostasy Models -- LLRA Model -- ELRA Model -- LLDA Model -- ELDA Model -- Analytical Solution for the Local Lithosphere -- Numerical Methods -- Local Lithosphere -- Elastic Lithosphere -- Relaxing Asthenosphere -- Diffusive Asthenosphere -- Model Intercomparison -- Advanced Topics -- Induced Anisotropy -- Background -- Anisotropic Generalisation of Glen's Flow Law -- Proof of Anisotropy for the CAFFE Flow Law -- Some Examples -- Evolution of Anisotropy -- Application to the EDML Core, Antarctica -- Compressible Firn -- Background -- Densification of Firn -- Constitutive Relation for Firn -- Field Equations -- Parallel Sided Slab -- Temperate and Polythermal Glaciers -- Background -- Temperate Ice -- Temperate Ice Surface -- Temperate Ice Base -- Transition Conditions at the CTS -- Parallel Sided Polythermal Slab -- Polythermal Glaciers. , Enthalpy Formulation -- Conclusions, Summary and Outlook -- References Cited or Recommended -- List of Symbols -- List of Acronyms -- Index.
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  • 2
    Publication Date: 2021-01-08
    Description: 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: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2021-01-08
    Description: The sea level contribution of the Antarctic ice sheet constitutes a large uncertainty in future sea level projections. Here we apply a linear response theory approach to 16 state-of-the-art ice sheet models to estimate the Antarctic ice sheet contribution from basal ice shelf melting within the 21st century. The purpose of this computation is to estimate the uncertainty of Antarctica's future contribution to global sea level rise that arises from large uncertainty in the oceanic forcing and the associated ice shelf melting. Ice shelf melting is considered to be a major if not the largest perturbation of the ice sheet's flow into the ocean. However, by computing only the sea level contribution in response to ice shelf melting, our study is neglecting a number of processes such as surface-mass-balance-related contributions. In assuming linear response theory, we are able to capture complex temporal responses of the ice sheets, but we neglect any self-dampening or self-amplifying processes. This is particularly relevant in situations in which an instability is dominating the ice loss. The results obtained here are thus relevant, in particular wherever the ice loss is dominated by the forcing as opposed to an internal instability, for example in strong ocean warming scenarios. In order to allow for comparison the methodology was chosen to be exactly the same as in an earlier study (Levermann et al., 2014) but with 16 instead of 5 ice sheet models. We include uncertainty in the atmospheric warming response to carbon emissions (full range of CMIP5 climate model sensitivities), uncertainty in the oceanic transport to the Southern Ocean (obtained from the time-delayed and scaled oceanic subsurface warming in CMIP5 models in relation to the global mean surface warming), and the observed range of responses of basal ice shelf melting to oceanic warming outside the ice shelf cavity. This uncertainty in basal ice shelf melting is then convoluted with the linear response functions of each of the 16 ice sheet models to obtain the ice flow response to the individual global warming path. The model median for the observational period from 1992 to 2017 of the ice loss due to basal ice shelf melting is 10.2 mm, with a likely range between 5.2 and 21.3 mm. For the same period the Antarctic ice sheet lost mass equivalent to 7.4 mm of global sea level rise, with a standard deviation of 3.7 mm (Shepherd et al., 2018) including all processes, especially surface-mass-balance changes. For the unabated warming path, Representative Concentration Pathway 8.5 (RCP8.5), we obtain a median contribution of the Antarctic ice sheet to global mean sea level rise from basal ice shelf melting within the 21st century of 17 cm, with a likely range (66th percentile around the mean) between 9 and 36 cm and a very likely range (90th percentile around the mean) between 6 and 58 cm. For the RCP2.6 warming path, which will keep the global mean temperature below 2 ∘C of global warming and is thus consistent with the Paris Climate Agreement, the procedure yields a median of 13 cm of global mean sea level contribution. The likely range for the RCP2.6 scenario is between 7 and 24 cm, and the very likely range is between 4 and 37 cm. The structural uncertainties in the method do not allow for an interpretation of any higher uncertainty percentiles. We provide projections for the five Antarctic regions and for each model and each scenario separately. The rate of sea level contribution is highest under the RCP8.5 scenario. The maximum within the 21st century of the median value is 4 cm per decade, with a likely range between 2 and 9 cm per decade and a very likely range between 1 and 14 cm per decade.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 4
    Publication Date: 2020-02-27
    Description: The sea level contribution of the Antarctic ice sheet constitutes a large uncertainty in future sea level projections. Here we apply a linear response theory approach to 16 state-of-the-art ice sheet models to estimate the Antarctic ice sheet contribution from basal ice shelf melting within the 21st century. The purpose of this computation is to estimate the uncertainty of Antarctica's future contribution to global sea level rise that arises from large uncertainty in the oceanic forcing and the associated ice shelf melting. Ice shelf melting is considered to be a major if not the largest perturbation of the ice sheet's flow into the ocean. However, by computing only the sea level contribution in response to ice shelf melting, our study is neglecting a number of processes such as surface-mass-balance-related contributions. In assuming linear response theory, we are able to capture complex temporal responses of the ice sheets, but we neglect any self-dampening or self-amplifying processes. This is particularly relevant in situations in which an instability is dominating the ice loss. The results obtained here are thus relevant, in particular wherever the ice loss is dominated by the forcing as opposed to an internal instability, for example in strong ocean warming scenarios. In order to allow for comparison the methodology was chosen to be exactly the same as in an earlier study (Levermann et al., 2014) but with 16 instead of 5 ice sheet models. We include uncertainty in the atmospheric warming response to carbon emissions (full range of CMIP5 climate model sensitivities), uncertainty in the oceanic transport to the Southern Ocean (obtained from the time-delayed and scaled oceanic subsurface warming in CMIP5 models in relation to the global mean surface warming), and the observed range of responses of basal ice shelf melting to oceanic warming outside the ice shelf cavity. This uncertainty in basal ice shelf melting is then convoluted with the linear response functions of each of the 16 ice sheet models to obtain the ice flow response to the individual global warming path. The model median for the observational period from 1992 to 2017 of the ice loss due to basal ice shelf melting is 10.2 mm, with a likely range between 5.2 and 21.3 mm. For the same period the Antarctic ice sheet lost mass equivalent to 7.4 mm of global sea level rise, with a standard deviation of 3.7 mm (Shepherd et al., 2018) including all processes, especially surface-mass-balance changes. For the unabated warming path, Representative Concentration Pathway 8.5 (RCP8.5), we obtain a median contribution of the Antarctic ice sheet to global mean sea level rise from basal ice shelf melting within the 21st century of 17 cm, with a likely range (66th percentile around the mean) between 9 and 36 cm and a very likely range (90th percentile around the mean) between 6 and 58 cm. For the RCP2.6 warming path, which will keep the global mean temperature below 2 ∘C of global warming and is thus consistent with the Paris Climate Agreement, the procedure yields a median of 13 cm of global mean sea level contribution. The likely range for the RCP2.6 scenario is between 7 and 24 cm, and the very likely range is between 4 and 37 cm. The structural uncertainties in the method do not allow for an interpretation of any higher uncertainty percentiles. We provide projections for the five Antarctic regions and for each model and each scenario separately. The rate of sea level contribution is highest under the RCP8.5 scenario. The maximum within the 21st century of the median value is 4 cm per decade, with a likely range between 2 and 9 cm per decade and a very likely range between 1 and 14 cm per decade.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Format: application/pdf
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