scholarly journals Transient glacier response with a higher-order numerical ice-flow model

2002 ◽  
Vol 48 (162) ◽  
pp. 467-477 ◽  
Author(s):  
Frank Pattyn
Keyword(s):  
Flow Model ◽  
Higher Order ◽  
Ice Flow ◽  
Surface Mass ◽  
Front Position ◽  
Significant Difference ◽  
Dynamic Experiments ◽  
Stress Profiles ◽  
Horizontal Grid ◽  
Higher Order Models

AbstractIn this paper, a higher-order numerical flowline model is presented which is numerically stable and fast and can cope with very small horizontal grid sizes (<10 m). The model is compared with the results from Blatter and others (1998) on Haut Glacier d’Arolla, Switzerland, and with the European Ice-Sheet Modelling Initiative benchmarks (Huybrechts and others, 1996). Results demonstrate that the significant difference between calculated basal-drag and driving-stress profiles in a fixed geometry disappears when the glacier profile is allowed to react to the surface mass-balance conditions and reaches a steady state. Dynamic experiments show that the mass transfer in higher-order models occurs at a different speed in the accumulation and ablation areas and that the front position is more sensitive to migration compared to the shallow-ice approximation.

scholarly journals Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

2015 ◽  
Vol 11 (10) ◽  
pp. 1395-1416 ◽  
Author(s):  
S. Fujita ◽  
F. Parrenin ◽  
M. Severi ◽  
H. Motoyama ◽  
E. W. Wolff
Keyword(s):  
Age Differences ◽  
Flow Model ◽  
Ice Cores ◽  
Ice Flow ◽  
Surface Mass ◽  
The Past ◽  
The One ◽  
Mis 5E ◽  
Age Constraints ◽  
Mis 5

Abstract. Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d–6. Therefore, we hypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d–6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, −230 years (minimum) at MIS 7a and +60 to +126 years on average.

scholarly journals A system of conservative regridding for ice/atmosphere coupling in a GCM

2013 ◽  
Vol 6 (4) ◽  
pp. 6493-6568 ◽  
Author(s):  
R. Fischer ◽  
S. Nowicki ◽  
M. Kelley ◽  
G. A. Schmidt
Keyword(s):  
Finite Element ◽  
General Circulation ◽  
Flow Model ◽  
Source Code ◽  
Circulation Model ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass ◽  
Flow Models ◽  
Ice Model

Abstract. The method of elevation classes has proven to be a useful way for a low-resolution general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields, for use in one-way studies coupling GCMs and ice flow models. Past uses of elevation classes have been a cause of non-conservation of mass and energy, caused by inconsistency in regridding schemes chosen to regrid to the atmosphere vs. downscaling to the ice model. This causes problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded, and five transformations between those grids required by a typical coupled GCM–ice flow model. This paper shows how each of those transformations may be achieved in a consistent, conservative manner. These transformations are implemented in GLINT2, a library used to couple GCMs with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

scholarly journals Assessing Controls on Ice Dynamics at Crane Glacier, Antarctic Peninsula Using a Numerical Ice Flow Model

2021 ◽  
Author(s):  
Rainey Aberle
Keyword(s):  
Antarctic Peninsula ◽  
Flow Model ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Climate Conditions ◽  
Ice Shelves ◽  
Tidewater Glacier ◽  
Mass Discharge

The widespread retreat of glaciers and the collapse of ice shelves along the Antarctic Peninsula has been attributed to atmospheric and oceanic warming, which promotes mass loss. However, several glaciers on the eastern peninsula that were buttressed by the Larsen A and B ice shelves prior to collapse in 1995 and 2002, respectively, have been advancing in recent years. This asymmetric pattern of rapid retreat and long-term re-advance is similar to the tidewater glacier cycle, which can occur largely independent of climate forcing. Here, I use a width- and depth-integrated numerical ice flow model to investigate glacier response to ice shelf collapse and the influence of changing climate conditions at Crane Glacier, formerly a tributary of the Larsen B ice shelf, over the last ~10 years. Sensitivity tests to explore the influence of perturbations in surface mass balance and submarine melt (up to 10 m a-1) and fresh water impounded in crevasses (up to 10 m) on glacier dynamics reveal that by 2100, the modeled mass discharge ranges from 0.53-98 Gt a-1, with the most substantial changes due to surface melt-induced thinning. My findings suggest that the growth of a floating ice tongue can hinder enhanced flow, allowing the grounding zone to remain steady for many decades, analogous to the advancing stage of the tidewater glacier cycle. Additionally, former tributary glaciers can take several decades to geometrically adjust to ice shelf collapse at their terminal boundary while elevated glacier discharge persists.

scholarly journals Ice flow modelling to constrain the surface mass balance and ice discharge of San Rafael Glacier, Northern Patagonia Icefield

2018 ◽  
Vol 64 (246) ◽  
pp. 568-582 ◽  
Author(s):  
GABRIELA COLLAO-BARRIOS ◽  
FABIEN GILLET-CHAULET ◽  
VINCENT FAVIER ◽  
GINO CASASSA ◽  
ETIENNE BERTHIER ◽  
...  
Keyword(s):  
Mass Balance ◽  
Flow Model ◽  
Surface Velocity ◽  
Shear Stresses ◽  
Surface Mass Balance ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Northern Patagonia ◽  
San Rafael

ABSTRACTWe simulate the ice dynamics of the San Rafael Glacier (SRG) in the Northern Patagonia Icefield (46.7°S, 73.5°W), using glacier geometry obtained by airborne gravity measurements. The full-Stokes ice flow model (Elmer/Ice) is initialized using an inverse method to infer the basal friction coefficient from a satellite-derived surface velocity mosaic. The high surface velocities (7.6 km a−1) near the glacier front are explained by low basal shear stresses (<25 kPa). The modelling results suggest that 98% of the surface velocities are due to basal sliding in the fast-flowing glacier tongue (>1 km a−1). We force the model using different surface mass-balance scenarios taken or adapted from previous studies and geodetic elevation changes between 2000 and 2012. Our results suggest that previous estimates of average surface mass balance over the entire glacier (Ḃ) were likely too high, mainly due to an overestimation in the accumulation area. We propose that most of SRG imbalance is due to the large ice discharge (−0.83 ± 0.08 Gt a−1) and a slightly positiveḂ(0.08 ± 0.06 Gt a−1). The committed mass-loss estimate over the next century is −0.34 ± 0.03 Gt a−1. This study demonstrates that surface mass-balance estimates and glacier wastage projections can be improved using a physically based ice flow model.

scholarly journals Modelling debris transport within glaciers by advection in a full-Stokes ice flow model

2018 ◽  
Vol 12 (1) ◽  
pp. 189-204 ◽  
Author(s):  
Anna Wirbel ◽  
Alexander H. Jarosch ◽  
Lindsey Nicholson
Keyword(s):  
Flow Model ◽  
Glacier Surface ◽  
Ice Flow ◽  
Transport Pathways ◽  
Surface Mass ◽  
Glacier System ◽  
Debris Cover ◽  
Debris Transport ◽  
Extensive Surface ◽  
Paleoclimate Proxy

Abstract. Glaciers with extensive surface debris cover respond differently to climate forcing than those without supraglacial debris. In order to include debris-covered glaciers in projections of glaciogenic runoff and sea level rise and to understand the paleoclimate proxy recorded by such glaciers, it is necessary to understand the manner and timescales over which a supraglacial debris cover develops. Because debris is delivered to the glacier by processes that are heterogeneous in space and time, and these debris inclusions are altered during englacial transport through the glacier system, correctly determining where, when and how much debris is delivered to the glacier surface requires knowledge of englacial transport pathways and deformation. To achieve this, we present a model of englacial debris transport in which we couple an advection scheme to a full-Stokes ice flow model. The model performs well in numerical benchmark tests, and we present both 2-D and 3-D glacier test cases that, for a set of prescribed debris inputs, reproduce the englacial features, deformation thereof and patterns of surface emergence predicted by theory and observations of structural glaciology. In a future step, coupling this model to (i) a debris-aware surface mass balance scheme and (ii) a supraglacial debris transport scheme will enable the co-evolution of debris cover and glacier geometry to be modelled.

PoLIM: an open source 2D higher-order thermomechanically coupled mountain glacier flow model

2020 ◽  
Author(s):  
Yuzhe Wang ◽  
Tong Zhang
Keyword(s):  
Flow Model ◽  
Order Approximation ◽  
Water Pressure ◽  
Computational Cost ◽  
Higher Order ◽  
Thermomechanical Coupling ◽  
High Mountain ◽  
Climate Data ◽  
Mountain Glacier ◽  
Ice Flow

&lt;p&gt;The worldwide glacier is retreating and is expected to continue shrinking in a warming climate. Understanding the dynamics of glaciers is essential for the knowledge of sea-level rise, water resources in high mountain and arid regions, and the potential glacier hazards. Over the past decades, various 3D higher-order and full-Stokes ice flow models including thermomechanical coupling have been developed, and some have opened their source codes. However, such 3D modeling requires detailed datasets about surface and bedrock topography, variable climatic conditions, and high computational cost. Due to difficulties in measuring glacier thickness, only a small minority of glaciers around the globe have ice thickness observations. It is also a challenge to downscale the climate data (e.g., air temperature, precipitation) to the glacier surface, particularly, in rugged high-mountain terrains. In contrast to 3D models, flowline models only require inputs along the longitudinal profile and are thus computationally efficient. They continue to be useful tools for simulating the evolution of glaciers and studying the particular phenomena related to glacier dynamics. In this study, we present a two-dimensional thermomechanically coupled ice flow model named PoLIM (Polythermal Land Ice Model). The velocity solver of PoLIM is developed based on the higher-order approximation (Blatter-Pattyn type). It includes three critical features for simulating the dynamics of mountain glaciers: 1) an enthalpy-based thermal model to describe the heat transfer, which is particularly convenient to simulate the polythermal structures; 2) a drainage model to simulate the water transport in the temperate ice layer driven by gravity; 3) a subglacial hydrology model to simulate the subglacial water pressure for the coupling with the basal sliding law. We verify PoLIM with several standard benchmark experiments (e.g., ISMIP-HOM, enthalpy, SHMIP) in the glacier modeling community. PoLIM shows a good performance and agrees well with these benchmark results, indicating its reliable and robust capability of simulating the thermomechanical behaviors of glaciers.&lt;/p&gt;

scholarly journals Using the unstable manifold correction in a Picard iteration to solve the velocity field in higher-order ice-flow models

2010 ◽  
Vol 56 (196) ◽  
pp. 257-261 ◽  
Author(s):  
Bert De Smedt ◽  
Frank Pattyn ◽  
Pieter De Groen
Keyword(s):  
Velocity Field ◽  
Unstable Manifold ◽  
Real Data ◽  
Higher Order ◽  
Picard Iteration ◽  
Ice Flow ◽  
Flow Models ◽  
Original Algorithm ◽  
Fast Solution ◽  
Higher Order Models

AbstractWe address the usefulness of the unstable manifold correction (UMC) in a Picard iteration for the solution of the velocity field in higher-order ice-flow models. We explain under- and overshooting and how one can remedy them. We then discuss the rationale behind the UMC, initially developed to remedy overshooting, and how it was previously introduced in a Picard iteration to calculate the velocity field in higher-order models. Using a laminar-flow experiment with two higher-order model implementations, we demonstrate that it is not overshooting, but undershooting, that is the main problem when using a proper implementation for the calculation of the velocity field in higher-order models. We also consider a variant of the original UMC algorithm that often enables a relatively fast solution, but is theoretically less sound. Therefore, neither the variant nor the original algorithm is suited for these problems. We present a more appropriate, stable and simple relaxed Picard algorithm and demonstrate that, compared to the true Picard iteration and the variant of the original UMC algorithm, it results in a faster solution of the velocity field in higher-order models for problems with real data.

A two-dimensional, higher-order, enthalpy-based thermomechanical ice flow model for mountain glaciers and its benchmark experiments

2020 ◽  
Vol 141 ◽  
pp. 104526 ◽  
Author(s):  
Yuzhe Wang ◽  
Tong Zhang ◽  
Cunde Xiao ◽  
Jiawen Ren ◽  
Yanfen Wang
Keyword(s):  
Flow Model ◽  
Higher Order ◽  
Two Dimensional ◽  
Ice Flow ◽  
Mountain Glaciers

The zero-ice ice-flow problem

2020 ◽  
Author(s):  
G. Hilmar Gudmundsson
Keyword(s):  
Lagrange Multipliers ◽  
Flow Model ◽  
Unsolved Problem ◽  
Flow Problem ◽  
Higher Order ◽  
Ice Thickness ◽  
Active Set ◽  
Ice Flow ◽  
Active Set Method ◽  
Constrained Optimisation

&lt;p&gt;When modelling ice flow, one often encounters the situation where melt is applied over ice-free areas. For example, determining the terminus position of a glacier involves finding the locations where applied surface melt and ice flow produces areas of zero ice thickness. How to best deal numerically this situation without producing negative ice thickness is an open and unsolved problem. One approach is to impose positive ice-thickness constraints and reformulating the problem as a constrained optimisation problem using the active-set method. This approach is, for example, used in the ice flow model &amp;#218;a. &amp;#160;I&amp;#8217;ll provide an overview over the approach used in the model and explain some difficulties, and how these have been addressed, associated with the use of higher order elements where the sign of the Lagrange multipliers can not be used to identify the active set.&lt;/p&gt;

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