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  • 1
    Online Resource
    Online Resource
    Berlin, Heidelberg :Springer Berlin / Heidelberg,
    Keywords: Geophysics--Mathematical models. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (401 pages)
    Edition: 1st ed.
    ISBN: 9783662044391
    DDC: 550.015118
    Language: English
    Note: Continuum Mechanics and Applications in Geophysics and the Environment -- Copyright -- Preface -- Contents -- List of Contributors -- Part I Applied Continuum Mechanics -- Numerical Investigation of Shock Waves in a Radiating Gas Described by a Variable Eddington Factor -- Anisotropic Fluids: From Liquid Crystals to Granular Materials -- Integration and Segregation in a Population - A Thermodynamicists's View -- Asymptotic and Other Properties of Some Nonlinear Diffusion Models -- The Binary Mixtures of Euler Fluids: A Unified Theory of Second Sound Phenomena -- Continuously Distributed Control of Plates by Electric Networks with PZT Actuators -- Part II Soil Mechanics and Porous Media -- Hydraulic Theory for a Frictional Debris Flow on a Collisional Shear Layer -- The Beavers and Joseph Condition for Velocity Slip at the Surface of a Porous Medium -- Porous Convection, the Chebyshev Tau Method, and Spurious Eigenvalues -- Mechanics of Multiphase Porous Media - Application to Unsaturated Soils -- Part III Glacier and Ice Dynamics -- Modelling Iceberg Drift and Ice-Rafted Sedimentation -- Modelling the Flow of Glaciers and Ice Sheets -- Notes on Basic Glaciological Computational Methods and Algorithms -- Constitutive Modelling and Flow Simulation of Anisotropic Polar Ice -- Influence of Bed Topography on Steady Plane Ice Sheet Flow -- Part IV Climatology and Lake Physics -- Glacial Isostasy: Models for the Response of the Earth to Varying Ice Loads -- Arctic Sea Ice and Its Role in Climate Variability and Change -- The Role of Simple Models in Understanding Climate Change -- Comparing Different Numerical Treatments of Advection Terms for Wind-Induced Circulations in Lake Constance.
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  • 2
    In: Expedition Erde, Bremen : MARUM - Zentrum für Marine Umweltwissenschaften, 2015, (2015), Seite 352-359, 9783000490453
    In: year:2015
    In: pages:352-359
    Type of Medium: Article
    Pages: Ill.
    Language: German
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 46 (2000), S. 289-303 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Numerical computations are performed with the three-dimensional polythermal ice-sheet model SICOPOLIS in order to investigate the possible impact of a greenhouse-gas-induced climate change on the Greenland ice sheet. The assumed increase of the mean annual air temperature above the ice covers a range from ΔT = 1°C to 12°C, and several parameterizations for the snowfall and the surface melting are considered. The simulated shrinking of the ice sheet is a smooth function of the temperature rise, indications for the existence of critical thresholds of the climate input are not found. Within 1000 model years, the ice-volume decrease is limited to 10% of the present volume for ΔT ≤ 3°C, whereas the most extreme scenario, ΔT = 12°C, leads to an almost entire disintegration, which corresponds to a sea-level equivalent of 7 m. The different snowfall and melting parameterizations yield an uncertainty range of up to 20% of the present ice volume after 1000 model years.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2018-12-17
    Description: The shallow ice approximation (SIA) is commonly used in ice-sheet models to simplify the force balance equations within the ice. However, the SIA cannot adequately reproduce the dynamics of the fast flowing ice streams usually found at the margins of ice sheets. To overcome this limitation, recent studies have introduced heuristic hybrid combinations of the SIA and the shelfy stream approximation. Here, we implement four different hybrid schemes into a model of the Antarctic Ice Sheet in order to compare their performance under present-day conditions. For each scheme, the model is calibrated using an iterative technique to infer the spatial variability in basal sliding parameters. Model results are validated against topographic and velocity data. Our analysis shows that the iterative technique compensates for the differences between the schemes, producing similar ice-sheet configurations through quantitatively different results of the sliding coefficient calibration. Despite this we observe a robust agreement in the reconstructed patterns of basal sliding parameters. We exchange the calibrated sliding parameter distributions between the schemes to demonstrate that the results of the model calibration cannot be straightforwardly transferred to models based on different approximations of ice dynamics. However, easily adaptable calibration techniques for the potential distribution of basal sliding coefficients can be implemented into ice models to overcome such incompatibility, as shown in this study
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2018-12-17
    Description: Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.
    Type: Article , PeerReviewed
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  • 7
    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
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  • 8
    Publication Date: 2021-01-08
    Description: Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2018-09-03
    Description: We introduce the coupled model of the Greenland glacial system IGLOO 1.0, including the polythermal ice sheet model SICOPOLIS (version 3.3) with hybrid dynamics, the model of basal hydrology HYDRO and a parameterization of submarine melt for marine-terminated outlet glaciers. Aim of this glacial system model is to gain a better understanding of the processes important for the future contribution of the Greenland ice sheet to sea level rise under future climate change scenarios. The ice sheet is initialized via a relaxation towards observed surface elevation, imposing the palaeo-surface temperature over the last glacial cycle. As a present-day reference, we use the 1961-1990 standard climatology derived from simulations of the regional atmosphere model MAR with ERA reanalysis boundary conditions. For the palaeo-part of the spin-up, we add the temperature anomaly derived from the GRIP ice core to the years 1961–1990 average surface temperature field. For our projections, we apply surface temperature and surface mass balance anomalies derived from RCP 4.5 and RCP 8.5 scenarios created by MAR with boundary conditions from simulations with three CMIP5 models. The hybrid ice sheet model is fully coupled with the model of basal hydrology. With this model and the MAR scenarios, we perform simulations to estimate the contribution of the Greenland ice sheet to future sea level rise until the end of the 21st and 23rd centuries. Further on, the impact of elevation-surface mass balance feedback, introduced via the MAR data, on future sea level rise is inspected. In our projections, we found the Greenland ice sheet to contribute to global sea level rise between 1.9 and 13.0cm until the year 2100 and between 3.5 and 76.4cm until the year 2300, including our simulated additional sea level rise due to elevation-surface mass balance feedback. Translated into additional sea level rise, the strength of this feedback in the year 2100 varies from 0.4 to 1.7cm, and in the year 2300 it ranges from 1.7 to 21.8cm. Additionally, taking Helheim and Store Glaciers as examples, we investigate the role of ocean warming and surface runoff change for the melting of outlet glaciers. It shows that ocean temperature and subglacial discharge are about equally important for the melting of the examined outlet glaciers.
    Type: Article , NonPeerReviewed
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  • 10
    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
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