Benchmarking the vertically integrated ice-sheet model IMAU-ICE (version 2.0)

Abstract. Ice-dynamical processes constitute a large uncertainty in future projections of sea-level rise caused by anthropogenic climate change. Improving our understanding of these processes requires ice-sheet models that perform well at simulating both past and future ice-sheet evolution. Here, we present version 2.0 of the ice-sheet model IMAU-ICE, which uses the depth-integrated viscosity approximation (DIVA) to solve the stress balance. We evaluate its performance in a range of benchmark experiments, including simple analytical solutions, as well as both schematic and realistic model intercomparison exercises. IMAU-ICE has adopted recent developments in the numerical treatment of englacial stress and sub-shelf melt near the grounding-line, which result in good performance in experiments concerning grounding-line migration (MISMIP) and buttressing (ABUMIP). This makes it a model that is robust, versatile, and user-friendly, and which will provide a firm basis for (palaeo-)glaciological research in the coming years.

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Simulating detailed spatial patterns of ice shelf basal melt

10.5194/egusphere-egu21-4750 ◽

2021 ◽

Author(s):

Erwin Lambert ◽

André Jüling ◽

Paul Holland ◽

Roderik van de Wal

Keyword(s):

Flow Direction ◽

Ice Sheet ◽

Realistic Model ◽

Western Boundary ◽

Layer Model ◽

Ice Shelf ◽

Amundsen Sea ◽

Ice Shelves ◽

Grounding Line ◽

Ocean Properties

<p>The contact between ice shelves and relatively warm ocean waters causes basal melt, ice shelf thinning, and ultimately ice sheet mass loss. This basal melt, and its dependence on ocean properties, is poorly understood due to an overall lack of direct observations and a difficulty in explicit simulation of the circulation in sub-shelf cavities. In this study, we compare a number of parameterisations and models of increasing complexity, up to a 2D &#8216;Layer&#8217; model. Each model is aimed at quantifying basal melt rates as a function of offshore temperature and salinity. We test these models in an idealised setting (ISOMIP+) and in a realistic setting for the Amundsen Sea Embayment. All models show a comparable non-linear sensitivity of ice-shelf average basal melt to ocean warming, indicating a positive feedback between melt and circulation. However, the Layer model is the only one which explicitly resolves the flow direction of the buoyant melt plumes, which is primarily governed by rotation and by the basal topography of the ice shelves. At 500m resolution, this model simulates locally enhanced basal melt near the grounding line, in topographical channels, and near the western boundary. The simulated melt patterns for the Amundsen Sea ice shelves are compared to satellite observations of ice shelf thinning and to 3D numerical simulations of the sub-shelf cavity circulation. As detailed melt rates near the grounding line are essential for the stability of ice sheets, spatially realistic melt rates are crucial for future projections of ice sheet dynamics. We conclude that the Layer model can function as a relatively cheap yet realistic model to downscale 3D ocean simulations of ocean properties to sub-kilometer scale basal melt fields to provide detailed forcing fields to ice sheet models.</p>

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The GRISLI ice sheet model (version 2.0): calibration and validation for multi-millennial changes of the Antarctic ice sheet

10.5194/gmd-2018-105 ◽

2018 ◽

Cited By ~ 1

Author(s):

Aurélien Quiquet ◽

Christophe Dumas ◽

Catherine Ritz ◽

Vincent Peyaud ◽

Didier M. Roche

Keyword(s):

Ice Sheet ◽

Climate Forcing ◽

Antarctic Ice Sheet ◽

Ice Volume ◽

Grounding Line ◽

Version 2.0 ◽

The Antarctic ◽

Climate Proxies ◽

Ice Model

Abstract. In this paper we present the GRISLI (Grenoble Ice Sheet and Land Ice) model in its newest revision (version 2.0). Whilst GRISLI is applicable to any given geometry, we focus here on the Antarctic ice sheet because it highlights the importance of grounding line dynamics. Important improvements have been implemented since its original version (Ritz et al., 2001) including notably an explicit flux computation at the grounding line based on the analytical formulations of Schoof (2007) and Tsai et al. (2015) and a basal hydrology model. A calibration of the mechanical parameters of the model based on an ensemble of 150 members sampled with a Latin Hypercube method is used. The ensemble members performance is assessed relative to the deviation from present-day observed Antarctic ice thickness. The model being designed for multi-millenial long- term integrations, we also present glacial-interglacial ice sheet changes throughout the last 400 kyr using the best ensemble members. To achieve this goal, we construct a simple climatic perturbation of present-day climate forcing fields based on two climate proxies, both atmospheric and oceanic. The model is able to reproduce expected grounding line advances during glacials and subsequent retreats during terminations with reasonable glacial-interglacial ice volume changes.

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The GRISLI ice sheet model (version 2.0): calibration and validation for multi-millennial changes of the Antarctic ice sheet

Geoscientific Model Development ◽

10.5194/gmd-11-5003-2018 ◽

2018 ◽

Vol 11 (12) ◽

pp. 5003-5025 ◽

Cited By ~ 6

Author(s):

Aurélien Quiquet ◽

Christophe Dumas ◽

Catherine Ritz ◽

Vincent Peyaud ◽

Didier M. Roche

Keyword(s):

Ice Sheet ◽

Climate Forcing ◽

Method Performance ◽

Antarctic Ice Sheet ◽

Grounding Line ◽

Version 2.0 ◽

Glacial Periods ◽

The Antarctic ◽

Climate Proxies

Abstract. In this paper, we present the GRISLI (Grenoble ice sheet and land ice) model in its newest revision (version 2.0). Whilst GRISLI is applicable to any given ice sheet, we focus here on the Antarctic ice sheet because it highlights the importance of grounding line dynamics. Important improvements have been implemented in the model since its original version (Ritz et al., 2001). Notably, GRISLI now includes a basal hydrology model and an explicit flux computation at the grounding line based on the analytical formulations of Schoof (2007) or Tsai et al. (2015). We perform a full calibration of the model based on an ensemble of 300 simulations sampling mechanical parameter space using a Latin hypercube method. Performance of individual members is assessed relative to the deviation from present-day observed Antarctic ice thickness. To assess the ability of the model to simulate grounding line migration, we also present glacial–interglacial ice sheet changes throughout the last 400 kyr using the best ensemble members taking advantage of the capacity of the model to perform multi-millennial long-term integrations. To achieve this goal, we construct a simple climatic perturbation of present-day climate forcing fields based on two climate proxies: atmospheric and oceanic. The model is able to reproduce expected grounding line advances during glacial periods and subsequent retreats during terminations with reasonable glacial–interglacial ice volume changes.

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Brief communication: Impact of mesh resolution for MISMIP and MISMIP3d experiments using Elmer/Ice

The Cryosphere ◽

10.5194/tc-10-307-2016 ◽

2016 ◽

Vol 10 (1) ◽

pp. 307-312 ◽

Cited By ~ 12

Author(s):

O. Gagliardini ◽

J. Brondex ◽

F. Gillet-Chaulet ◽

L. Tavard ◽

V. Peyaud ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheets ◽

Ice Sheet ◽

Model Intercomparison ◽

Model Sensitivity ◽

Close Vicinity ◽

Grounding Line ◽

Mesh Resolution ◽

Intercomparison Exercises

Abstract. The dynamical contribution of marine ice sheets to sea level rise is largely controlled by grounding line (GL) dynamics. Two marine ice sheet model intercomparison exercises, namely MISMIP and MISMIP3d, have been proposed to the community to test and compare the ability of models to capture the GL dynamics. Both exercises are known to present a discontinuity of the friction at the GL, which is believed to increase the model sensitivity to mesh resolution. Here, using Elmer/Ice, the only Stokes model which completed both intercomparisons, the sensitivity to the mesh resolution is studied from an extended MISMIP experiment in which the friction continuously decreases over a transition distance and equals zero at the GL. Using this MISMIP-like setup, it is shown that the sensitivity to the mesh resolution is not improved for a vanishing friction at the GL. For the original MISMIP experiment, i.e. for a discontinuous friction at the GL, we further show that the results are moreover very sensitive to the way the friction is interpolated in the close vicinity of the GL. In the light of these new insights, and thanks to increased computing resources, new results for the MISMIP3d experiments obtained for higher resolutions than previously published are made available for future comparisons as the Supplement.

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The Role of Web Based Accounting Online System 2.0 as the Company's Income and Expense Management

Aptisi Transactions on Management (ATM) ◽

10.33050/atm.v1i1.655 ◽

2017 ◽

Vol 1 (1) ◽

pp. 44-49

Author(s):

Nur Azizah ◽

Dedeh Supriyanti ◽

Siti Fairuz Aminah Mustapha ◽

Holly Yang

Keyword(s):

Financial Management ◽

Accounting System ◽

Bank Account ◽

Web Based ◽

Online System ◽

Version 2.0 ◽

User Friendly ◽

The Impact ◽

A Company

In a company, the process of income and expense of money must have a profit-generating goal base. The success of financial management within the company, can be monitored from the ability of the financial management in managing the finances and utilize all the opportunities that exist with as much as possible with the aim to control the company's cash (cash flow) and the impact of generating profits in accordance with expectations. With a web-based online accounting system version 2.0, companies can be given the ease to manage money in and out of the company's cash. It has a user friendly system with navigation that makes it easy for the financial management to use it. Starting from the creation of a company's cash account used as a cash account and corporate bank account on the system, deletion or filing of cash accounts, up to the transfer invoice creation feature, receive and send money. Thus, this system is very effective and efficient in the management of income and corporate cash disbursements. Keywords:Accounting Online System, Financial Management, Cash and Bank

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Results of the Marine Ice Sheet Model Intercomparison Project, MISMIP

The Cryosphere ◽

10.5194/tc-6-573-2012 ◽

2012 ◽

Vol 6 (3) ◽

pp. 573-588 ◽

Cited By ~ 146

Author(s):

F. Pattyn ◽

C. Schoof ◽

L. Perichon ◽

R. C. A. Hindmarsh ◽

E. Bueler ◽

...

Keyword(s):

Steady State ◽

Adaptive Mesh Refinement ◽

Ice Sheet ◽

Adaptive Mesh ◽

Stable Steady State ◽

Fixed Grid ◽

Approximate Analytical Solutions ◽

Grounding Line ◽

Intercomparison Project ◽

Line Positions

Abstract. Predictions of marine ice-sheet behaviour require models that are able to robustly simulate grounding line migration. We present results of an intercomparison exercise for 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 effects of lateral buttressing). Unique steady state grounding line positions exist for ice sheets on a downward sloping bed, while hysteresis occurs across an overdeepened bed, and stable steady state grounding line positions only occur on the downward-sloping sections. Models based on the shallow ice approximation, which does not resolve extensional stresses, do not reproduce the approximate analytical results unless appropriate parameterizations for ice flux are imposed at the grounding line. For extensional-stress resolving "shelfy stream" models, differences between model results were mainly due to the choice of spatial discretization. Moving grid methods were found to be the most accurate at capturing grounding line evolution, since they track the grounding line explicitly. Adaptive mesh refinement can further improve accuracy, including fixed grid models that generally perform poorly at coarse resolution. Fixed grid models, with nested grid representations of the grounding line, are able to generate accurate steady state positions, but can be inaccurate over transients. Only one full-Stokes model was included in the intercomparison, and consequently the accuracy of shelfy stream models as approximations of full-Stokes models remains to be determined in detail, especially during transients.

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Grounding-line retreat of the West Antarctic Ice Sheet from inner Pine Island Bay

Geology ◽

10.1130/g33469.1 ◽

2012 ◽

Vol 41 (1) ◽

pp. 35-38 ◽

Cited By ~ 51

Author(s):

C.-D. Hillenbrand ◽

G. Kuhn ◽

J. A. Smith ◽

K. Gohl ◽

A. G. C. Graham ◽

...

Keyword(s):

Ice Sheet ◽

The West ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

Grounding Line

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Dynamical processes involved in the retreat of marine ice sheets

Journal of Glaciology ◽

10.3189/172756501781832269 ◽

2001 ◽

Vol 47 (157) ◽

pp. 271-282 ◽

Cited By ~ 95

Author(s):

Richard C.A. Hindmarsh ◽

E. Le Meur

Keyword(s):

Ice Sheets ◽

Ice Sheet ◽

Ice Shelf ◽

Ice Streams ◽

Antarctic Ice Sheet ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

Grounding Line ◽

Neutral Equilibrium ◽

Generally True

AbstractMarine ice sheets with mechanics described by the shallow-ice approximation by definition do not couple mechanically with the shelf. Such ice sheets are known to have neutral equilibria. We consider the implications of this for their dynamics and in particular for mechanisms which promote marine ice-sheet retreat. The removal of ice-shelf buttressing leading to enhanced flow in grounded ice is discounted as a significant influence on mechanical grounds. Sea-level rise leading to reduced effective pressures under ice streams is shown to be a feasible mechanism for producing postglacial West Antarctic ice-sheet retreat but is inconsistent with borehole evidence. Warming thins the ice sheet by reducing the average viscosity but does not lead to grounding-line retreat. Internal oscillations either specified or generated via a MacAyeal–Payne thermal mechanism promote migration. This is a noise-induced drift phenomenon stemming from the neutral equilibrium property of marine ice sheets. This migration occurs at quite slow rates, but these are sufficiently large to have possibly played a role in the dynamics of the West Antarctic ice sheet after the glacial maximum. Numerical experiments suggest that it is generally true that while significant changes in thickness can be caused by spatially uniform changes, spatial variability coupled with dynamical variability is needed to cause margin movement.

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Response to Filchner-Ronne Ice Shelf cavity warming in a coupled ocean–ice sheet model. Part I: The ocean perspective

10.5194/os-2017-41 ◽

2017 ◽

Cited By ~ 1

Author(s):

Ralph Timmermann ◽

Sebastian Goeller

Keyword(s):

World Ocean ◽

Ice Sheet ◽

Coupled Model ◽

Freezing Temperature ◽

Ocean Model ◽

Climate Forcing ◽

Global Ocean ◽

Ice Shelf ◽

Marginal Seas ◽

Grounding Line

Abstract. A Regional Antarctic and Global Ocean (RAnGO) model has been developed to study the interaction between the world ocean and the Antarctic ice sheet. The coupled model is based on a global implementation of the Finite Element Sea-ice Ocean Model (FESOM) with a mesh refinement in the Southern Ocean, particularly in its marginal seas and in the sub-ice shelf cavities. The cryosphere is represented by a regional setup of the ice flow model RIMBAY comprising the Filchner-Ronne Ice Shelf and the grounded ice in its catchment area up to the ice divides. At the base of the RIMBAY ice shelf, melt rates from FESOM's ice-shelf component are supplied. RIMBAY returns ice thickness and the position of the grounding line. The ocean model uses a pre-computed mesh to allow for an easy adjustment of the model domain to a varying cavity geometry. RAnGO simulations with a 20th-century climate forcing yield realistic basal melt rates and a quasi-stable grounding line position close to the presently observed state. In a centennial-scale warm-water-inflow scenario, the model suggests a substantial thinning of the ice shelf and a local retreat of the grounding line. The potentially negative feedback from ice-shelf thinning through a rising in-situ freezing temperature is more than outweighed by the increasing water column thickness in the deepest parts of the cavity. Compared to a control simulation with fixed ice-shelf geometry, the coupled model thus yields a slightly stronger increase of ice-shelf basal melt rates.

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Modelling the response of the Lambert Glacier–Amery Ice Shelf system, East Antarctica, to uncertain climate forcing over the 21st and 22nd centuries

The Cryosphere ◽

10.5194/tc-8-1057-2014 ◽

2014 ◽

Vol 8 (3) ◽

pp. 1057-1068 ◽

Cited By ~ 20

Author(s):

Y. Gong ◽

S. L. Cornford ◽

A. J. Payne

Keyword(s):

Climate Model ◽

Global Environmental Change ◽

Ice Sheet ◽

Adaptive Mesh ◽

Ocean Model ◽

East Antarctica ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Grounding Line ◽

Lambert Glacier

Abstract. The interaction between the climate system and the large polar ice sheet regions is a key process in global environmental change. We carried out dynamic ice simulations of one of the largest drainage systems in East Antarctica: the Lambert Glacier–Amery Ice Shelf system, with an adaptive mesh ice sheet model. The ice sheet model is driven by surface accumulation and basal melt rates computed by the FESOM (Finite-Element Sea-Ice Ocean Model) ocean model and the RACMO2 (Regional Atmospheric Climate Model) and LMDZ4 (Laboratoire de Météorologie Dynamique Zoom) atmosphere models. The change of ice thickness and velocity in the ice shelf is mainly influenced by the basal melt distribution, but, although the ice shelf thins in most of the simulations, there is little grounding line retreat. We find that the Lambert Glacier grounding line can retreat as much as 40 km if there is sufficient thinning of the ice shelf south of Clemence Massif, but the ocean model does not provide sufficiently high melt rates in that region. Overall, the increased accumulation computed by the atmosphere models outweighs ice stream acceleration so that the net contribution to sea level rise is negative.

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