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 the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble

2018 ◽  
Author(s):  
Harry Zekollari ◽  
Matthias Huss ◽  
Daniel Farinotti
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Model Parameters ◽  
Surface Mass Balance ◽  
European Alps ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Future Evolution ◽  
The Future

Abstract. Glaciers in the European Alps play an important role in the hydrological cycle, act as a source for hydroelectricity and have a large touristic importance. The future evolution of these glaciers is driven by surface mass balance and ice flow processes, which the latter is to date not included in regional glacier projections for the Alps. Here, we model the future evolution of glaciers in the European Alps with GloGEMflow, an extended version of the Global Glacier Evolution Model (GloGEM), in which both surface mass balance and ice flow are explicitly accounted for. The mass balance model is calibrated with glacier-specific geodetic mass balances, and forced with high-resolution regional climate model (RCM) simulations from the EURO-CORDEX ensemble. The evolution of the total glacier volume in the coming decades is relatively similar under the various representative concentrations pathways (RCP2.6, 4.5 and 8.5), with volume losses of about 47–52 % in 2050 with respect to 2017. We find that under RCP2.6, the ice loss in the second part of the 21st century is relatively limited and that about one-third (36.8 % ± 11.1 %) of the present-day (2017) ice volume will still present in 2100. Under a strong warming (RCP8.5) the future evolution of the glaciers is dictated by a substantial increase in surface melt, and glaciers are projected to largely disappear by 2100 (94.4 ± 4.4 % volume loss vs. 2017). For a given RCP, differences in future changes are mainly determined by the driving global climate model, rather than by the RCM that is coupled to it, and these differences are larger than those arising from various model parameters. We find that under a limited warming, the inclusion of ice dynamics reduces the projected mass loss and that this effect increases with the glacier elevation range, implying that the inclusion of ice dynamics is likely to be important for global glacier evolution projections.

scholarly journals Modelling the future evolution of glaciers in the European Alps under the EURO-CORDEX RCM ensemble

2019 ◽  
Vol 13 (4) ◽  
pp. 1125-1146 ◽  
Author(s):  
Harry Zekollari ◽  
Matthias Huss ◽  
Daniel Farinotti
Keyword(s):  
Mass Balance ◽  
Climate Model ◽  
Model Parameters ◽  
Surface Mass Balance ◽  
European Alps ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass ◽  
Future Evolution ◽  
The Future

Abstract. Glaciers in the European Alps play an important role in the hydrological cycle, act as a source for hydroelectricity and have a large touristic importance. The future evolution of these glaciers is driven by surface mass balance and ice flow processes, of which the latter is to date not included explicitly in regional glacier projections for the Alps. Here, we model the future evolution of glaciers in the European Alps with GloGEMflow, an extended version of the Global Glacier Evolution Model (GloGEM), in which both surface mass balance and ice flow are explicitly accounted for. The mass balance model is calibrated with glacier-specific geodetic mass balances and forced with high-resolution regional climate model (RCM) simulations from the EURO-CORDEX ensemble. The evolution of the total glacier volume in the coming decades is relatively similar under the various representative concentrations pathways (RCP2.6, 4.5 and 8.5), with volume losses of about 47 %–52 % in 2050 with respect to 2017. We find that under RCP2.6, the ice loss in the second part of the 21st century is relatively limited and that about one-third (36.8 % ± 11.1 %, multi-model mean ±1σ) of the present-day (2017) ice volume will still be present in 2100. Under a strong warming (RCP8.5) the future evolution of the glaciers is dictated by a substantial increase in surface melt, and glaciers are projected to largely disappear by 2100 (94.4±4.4 % volume loss vs. 2017). For a given RCP, differences in future changes are mainly determined by the driving global climate model (GCM), rather than by the RCM, and these differences are larger than those arising from various model parameters (e.g. flow parameters and cross-section parameterisation). We find that under a limited warming, the inclusion of ice dynamics reduces the projected mass loss and that this effect increases with the glacier elevation range, implying that the inclusion of ice dynamics is likely to be important for global glacier evolution projections.

scholarly journals Surface Mass-Balance Gradients From Elevation and Ice Flux Data in the Columbia Basin, Canada

2021 ◽  
Vol 9 ◽  
Author(s):  
Ben M. Pelto ◽  
Brian Menounos
Keyword(s):  
Mass Balance ◽  
Numerical Models ◽  
Large Mass ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Ice Thickness ◽  
Surface Mass Balance ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Velocity

The mass-balance—elevation relation for a given glacier is required for many numerical models of ice flow. Direct measurements of this relation using remotely-sensed methods are complicated by ice dynamics, so observations are currently limited to glaciers where surface mass-balance measurements are routinely made. We test the viability of using the continuity equation to estimate annual surface mass balance between flux-gates in the absence of in situ measurements, on five glaciers in the Columbia Mountains of British Columbia, Canada. Repeat airborne laser scanning surveys of glacier surface elevation, ice penetrating radar surveys and publicly available maps of ice thickness are used to estimate changes in surface elevation and ice flux. We evaluate this approach by comparing modeled to observed mass balance. Modeled mass-balance gradients well-approximate those obtained from direct measurement of surface mass balance, with a mean difference of +6.6 ± 4%. Regressing modeled mass balance, equilibrium line altitudes are on average 15 m higher than satellite-observations of the transient snow line. Estimates of mass balance over flux bins compare less favorably than the gradients. Average mean error (+0.03 ± 0.07 m w.e.) between observed and modeled mass balance over flux bins is relatively small, yet mean absolute error (0.55 ± 0.18 m w.e.) and average modeled mass-balance uncertainty (0.57 m w.e.) are large. Mass conservation, assessed with glaciological data, is respected (when estimates are within 1σ uncertainties) for 84% of flux bins representing 86% of total glacier area. Uncertainty on ice velocity, especially for areas where surface velocity is low (&lt;10 m a−1) contributes the greatest error in estimating ice flux. We find that using modeled ice thicknesses yields comparable modeled mass-balance gradients relative to using observations of ice thickness, but we caution against over-interpreting individual flux-bin mass balances due to large mass-balance residuals. Given the performance of modeled ice thickness and the increasing availability of ice velocity and surface topography data, we suggest that similar efforts to produce mass-balance gradients using modern high-resolution datasets are feasible on larger scales.

scholarly journals Application of GRACE to the evaluation of an ice flow model of the Greenland Ice Sheet

2016 ◽  
Author(s):  
N.-J. Schlegel ◽  
D. N. Wiese ◽  
E. Y. Larour ◽  
M. M. Watkins ◽  
J. E. Box ◽  
...  
Keyword(s):  
Mass Balance ◽  
Flow Model ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Validation Data ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Surface Mass

Abstract. Quantifying the Greenland Ice Sheet’s future contribution to sea level rise is a challenging task that requires accurate estimates of ice flow sensitivity to climate change. Forward models of ice flow dynamics are promising tools for estimating future ice sheet behavior, yet confidence is low because evaluation of historical simulations is so challenging due to the scarcity of highly-resolved (spatially and temporally) continental-wide validation data. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained mass concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of estimated monthly global gravity fields. Specifically, the Jet Propulsion Laboratory’s JPL RL05M GRACE mascon solution (GRACE-JPL) now offers an opportunity for ice sheet model evaluation within independently resolved 300 km mascons. Here, we investigate how Greenland Ice Sheet mass balance captured through observations - GRACE-JPL - differs from that simulated by the ice flow model - the Ice Sheet System Model (ISSM). For the years 2003-2012, ISSM is forced with regional climate model (RCM) surface mass balance (SMB), and resulting mass balance is directly compared against GRACE-JPL within individual mascons. Overall, we find good agreement in the Northeast, Southwest, and the interior of the ice sheet, where mass balance is primarily controlled by SMB. In the Northwest, seasonal amplitudes match well, but trends in ISSM are muted relative to GRACE-JPL. In the Southeast, GRACE-JPL exhibits larger seasonal amplitude than that predicted by SMB while simultaneously having more pronounced trends. These results indicate that discrepancies in the Northwest are controlled by changes in ice dynamics that are not currently modeled by ISSM, i.e. transient processes driven by ice sheet hydrology and ice-ocean interaction, while discrepancies in the Southeast are controlled by a combination of these missing dynamics and errors in modeled SMB. Along the margins, we find that transient dynamics are responsible for consistent intra-annual variations in regional mass balance that ultimately contribute to the steeper negative mass trends observed by GRACE-JPL. Consequently, ice-ocean interactions and hydrologically-driven processes at relatively high (monthly-to-seasonal) temporal resolutions must be considered for improving upon ice flow models.

THE STUDIES OF SURFACE MASS BALANCE AND ICE FLOW ON GLACIERS AUSTRELOVéNBREEN AND PEDERSENBREEN, SVALBARD, ARCTIC

2010 ◽  
Vol 22 (1) ◽  
pp. 10-22 ◽  
Author(s):  
Mingxing Xu ◽  
Ming Yan ◽  
Jiawen Ren ◽  
Songtao Ai ◽  
Jiancheng Kang ◽  
...  
Keyword(s):  
Mass Balance ◽  
Surface Mass Balance ◽  
Ice Flow ◽  
Surface Mass

scholarly journals Surface elevation changes during 2007–13 on Bowdoin and Tugto Glaciers, northwestern Greenland

2016 ◽  
Vol 62 (236) ◽  
pp. 1083-1092 ◽  
Author(s):  
SHUN TSUTAKI ◽  
SHIN SUGIYAMA ◽  
DAIKI SAKAKIBARA ◽  
TAKANOBU SAWAGAKI
Keyword(s):  
Mass Balance ◽  
Satellite Observations ◽  
Surface Elevation ◽  
Surface Mass Balance ◽  
Elevation Change ◽  
Predominant Role ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Elevation Changes ◽  
Negative Surface

ABSTRACTTo quantify recent thinning of marine-terminating outlet glaciers in northwestern Greenland, we carried out field and satellite observations near the terminus of Bowdoin Glacier. These data were used to compute the change in surface elevation from 2007 to 2013 and this rate of thinning was then compared with that of the adjacent land-terminating Tugto Glacier. Comparing DEMs of 2007 and 2010 shows that Bowdoin Glacier is thinning more rapidly (4.1 ± 0.3 m a−1) than Tugto Glacier (2.8 ± 0.3 m a−1). The observed negative surface mass-balance accounts for <40% of the elevation change of Bowdoin Glacier, meaning that the thinning of Bowdoin Glacier cannot be attributable to surface melting alone. The ice speed of Bowdoin Glacier increases down-glacier, reaching 457 m a−1 near the calving front. This flow regime causes longitudinal stretching and vertical compression at a rate of −0.04 a−1. It is likely that this dynamically-controlled thinning has been enhanced by the acceleration of the glacier since 2000. Our measurements indicate that ice dynamics indeed play a predominant role in the rapid thinning of Bowdoin Glacier.

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 Present dynamics and future prognosis of a slowly surging glacier

2011 ◽  
Vol 5 (1) ◽  
pp. 299-313 ◽  
Author(s):  
G. E. Flowers ◽  
N. Roux ◽  
S. Pimentel ◽  
C. G. Schoof
Keyword(s):  
Mass Balance ◽  
Force Balance ◽  
Surface Velocity ◽  
Internal Dynamic ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Surface ◽  
Glacier Ice ◽  
Glacier Flow ◽  
Negative Balance

Abstract. Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence is not a direct response to the external climate forcing, but whose character (i.e. period, amplitude, mechanism) may depend on the glacier's environmental or climate setting. We examine the dynamics of a small (∼5 km2) valley glacier in Yukon, Canada, where two previous surges have been photographically documented and an unusually slow surge is currently underway. To characterize the dynamics of the present surge, and to speculate on the future of this glacier, we employ a higher-order flowband model of ice dynamics with a regularized Coulomb-friction sliding law in both diagnostic and prognostic simulations. Diagnostic (force balance) calculations capture the measured ice-surface velocity profile only when non-zero basal water pressures are prescribed over the central region of the glacier, coincident with where evidence of the surge has been identified. This leads to sliding accounting for 50–100% of the total surface motion in this region. Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface mass balance, reveal a significant role played by a bedrock ridge beneath the current equilibrium line of the glacier. Ice thickening occurs above the ridge in our simulations, until the net mass balance reaches sufficiently negative values. We suggest that the bedrock ridge may contribute to the propensity for surges in this glacier by promoting the development of the reservoir area during quiescence, and may permit surges to occur under more negative balance conditions than would otherwise be possible. Collectively, these results corroborate our interpretation of the current glacier flow regime as indicative of a slow surge that has been ongoing for some time, and support a relationship between surge incidence or character and the net mass balance. Our results also highlight the importance of glacier bed topography in controlling ice dynamics, as observed in many other glacier systems.

Impact of the choice of surface mass balance models and their calibration on large-scale glacier change projections

2021 ◽  
Author(s):  
Lilian Schuster ◽  
David Rounce ◽  
Fabien Maussion
Keyword(s):  
Mass Balance ◽  
Large Scale ◽  
Model Complexity ◽  
Model Parameters ◽  
Glacier Change ◽  
Surface Mass Balance ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Mass Balance Models ◽  
Intercomparison Study

&lt;p&gt;A recent large model intercomparison study (GlacierMIP) showed that differences between the glacier models is a dominant source of uncertainty for future glacier change projections, in particular in the first half of the century.&amp;#160; Each glacier model has their own unique set of process representations and climate forcing methodology, which makes it impossible to determine the model components that contribute most to the projection uncertainty. This study aims to improve our understanding of the sources of large scale glacier model uncertainty using the Open Global Glacier Model (OGGM), focussing on the surface mass balance (SMB) in a first step. We calibrate and run a set of interchangeable SMB model parameterizations (e.g. monthly vs. daily, constant vs. variable lapse rates, albedo, snowpack evolution and refreezing) under controlled boundary conditions. Based on ensemble approaches, we explore the influence of (i) the parameter calibration strategy and (ii) SMB model complexity on regional to global glacier change. These uncertainties are then put in relation to a qualitative selection of other model design choices, such as the forcing climate dataset and ice dynamics model parameters.&amp;#160;&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document