Volume changes of Vatnajökull ice cap, Iceland, due to surface mass balance, ice flow, and subglacial melting at geothermal areas

ABSTRACTMost Icelandic glaciers show high-accumulation rates during winter and strong surface melting during summer. Although it is difficult to establish and maintain mass-balance programs on these glaciers, mass-balance series do exist for several of the ice caps (Björnsson and others, 2013). We make use of the frequent volcanic eruptions in Iceland, which cause widespread internal tephra layers in the ice caps, to reconstruct the surface mass balance (SMB) in the ablation zone. This method requires information about surface geometry and ice velocity, derived from remote-sensing information. In addition, the emergence angle of the tephra layer needs to be known. As a proof-of-concept, we utilize a prominent tephra layer of the Mýrdalsjökull Ice Cap to infer local SMB estimates in the ablation area back to 1988. Using tephra-layer outcrop locations across the glacier at different points in time it is possible to determine local mass changes (loss and redistribution) for a large part of the ablation zone, without the use of historic elevation models, which often are not available.

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Estimation of Glacier Thickness From Surface Mass Balance and Ice Flow Velocities: A Case Study on Argentière Glacier, France

Frontiers in Earth Science ◽

10.3389/feart.2018.00112 ◽

2018 ◽

Vol 6 ◽

Cited By ~ 11

Author(s):

Antoine Rabatel ◽

Olivier Sanchez ◽

Christian Vincent ◽

Delphine Six

Keyword(s):

Mass Balance ◽

Surface Mass Balance ◽

Ice Flow ◽

Surface Mass ◽

Flow Velocities

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A regression model for the mass-balance distribution of the Vatnajökull ice cap, Iceland

Annals of Glaciology ◽

10.3189/172756403781815447 ◽

2003 ◽

Vol 37 ◽

pp. 189-193 ◽

Cited By ~ 10

Author(s):

Guðefinna Aðalgeirsdóttir ◽

G. Hilmar Gudmundsson ◽

Helgi Björnsson

Keyword(s):

Linear Regression ◽

Regression Model ◽

Mass Balance ◽

Surface Mass Balance ◽

Negative Mass ◽

Equilibrium Line Altitude ◽

Surface Mass ◽

Ice Cap ◽

Maximum Value ◽

Slope Direction

AbstractA non-linear regression model describing the mass-balance distribution of the whole Vatnajökull ice cap, Iceland, for the years 1992–2000 is presented. All available data from some 40 locations over this 9 year period were used to determine the parameters of the model. The regression model uses six adjustable parameters which all have a clear physical interpretation. They are the slope, direction and the height of the equilibrium-line altitude (ELA) plane, two altitude mass-balance gradients, and a maximum value of the surface mass balance. It is found that the temporal variation of the observed mass-balance distribution can be accurately described through annual shifts of the ELA. Annual shifts in ELA are on the order of 100 m, which is of the same magnitude as the change expected to be caused by the climate variation predicted during the next decades. A slight trend towards a more negative mass balance is detected during this 9 year period.

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Temporally stable surface mass balance asymmetry across an ice rise derived from radar internal reflection horizons through inverse modeling

Journal of Glaciology ◽

10.1017/jog.2016.41 ◽

2016 ◽

Vol 62 (233) ◽

pp. 525-534 ◽

Cited By ~ 5

Author(s):

DENIS CALLENS ◽

REINHARD DREWS ◽

EMMANUEL WITRANT ◽

MORGANE PHILIPPE ◽

FRANK PATTYN

Keyword(s):

Mass Balance ◽

Large Scale ◽

Optimization Technique ◽

Internal Reflection ◽

Asymmetric Distribution ◽

Surface Mass Balance ◽

Ice Flow ◽

Atmospheric Flow ◽

Surface Mass ◽

Ice Shelves

ABSTRACTIce rises are locally grounded parts of Antarctic ice shelves that play an important role in regulating ice flow from the continent towards the ocean. Because they protrude out of the otherwise horizontal ice shelves, ice rises induce an orographic uplift of the atmospheric flow, resulting in an asymmetric distribution of the surface mass balance (SMB). Here, we combine younger and older internal reflection horizons (IRHs) from radar to quantify this distribution in time and space across Derwael Ice Rise (DIR), Dronning Maud Land, Antarctica. We employ two methods depending on the age of the IRHs, i.e. the shallow layer approximation for the younger IRHs near the surface and an optimization technique based on an ice flow model for the older IRHs. We identify an SMB ratio of 2.5 between the flanks and the ice divide with the SMB ranging between 300 and 750 kg m−2 a−1. The SMB maximum is located on the upwind side, ~4 km offset to today's topographic divide. The large-scale asymmetry is consistently observed in time until 1966. The SMB from older IRHs is less-well constrained, but the asymmetry has likely persisted for >ka, indicating that DIR has been a stable features over long time spans.

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

10.5194/tc-2018-267 ◽

2018 ◽

Cited By ~ 1

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.

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Simulating ice thickness and velocity evolution of Upernavik Isstrøm 1849–2012 by forcing prescribed terminus positions in ISSM

The Cryosphere ◽

10.5194/tc-12-1511-2018 ◽

2018 ◽

Vol 12 (4) ◽

pp. 1511-1522 ◽

Cited By ~ 5

Author(s):

Konstanze Haubner ◽

Jason E. Box ◽

Nicole J. Schlegel ◽

Eric Y. Larour ◽

Mathieu Morlighem ◽

...

Keyword(s):

Mass Loss ◽

Mass Balance ◽

Surface Mass Balance ◽

Position Change ◽

Ice Flow ◽

Surface Mass ◽

Total Mass Loss ◽

Negative Surface ◽

Ice Velocity ◽

Glacier Velocity

Abstract. Tidewater glacier velocity and mass balance are known to be highly responsive to terminus position change. Yet it remains challenging for ice flow models to reproduce observed ice margin changes. Here, using the Ice Sheet System Model (Larour et al., 2012), we simulate the ice velocity and thickness changes of Upernavik Isstrøm (north-western Greenland) by prescribing a collection of 27 observed terminus positions spanning 164 years (1849–2012). The simulation shows increased ice velocity during the 1930s, the late 1970s and between 1995 and 2012 when terminus retreat was observed along with negative surface mass balance anomalies. Three distinct mass balance states are evident in the reconstruction: (1849–1932) with near zero mass balance, (1932–1992) with ice mass loss dominated by ice dynamical flow, and (1998–2012), when increased retreat and negative surface mass balance anomalies led to mass loss that was twice that of any earlier period. Over the multi-decadal simulation, mass loss was dominated by thinning and acceleration responsible for 70 % of the total mass loss induced by prescribed change in terminus position. The remaining 30 % of the total ice mass loss resulted directly from prescribed terminus retreat and decreasing surface mass balance. Although the method can not explain the cause of glacier retreat, it enables the reconstruction of ice flow and geometry during 1849–2012. Given annual or seasonal observed terminus front positions, this method could be a useful tool for evaluating simulations investigating the effect of calving laws.

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The Equation of Continuity and its Application to the Ice Sheet Near “byrd” Station, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000021055 ◽

1977 ◽

Vol 18 (80) ◽

pp. 359-371 ◽

Cited By ~ 49

Author(s):

I. M. Whillans

Keyword(s):

Steady State ◽

Mass Balance ◽

Ice Sheet ◽

Ice Thickness ◽

Surface Mass Balance ◽

Velocity Measurements ◽

Ice Flow ◽

Measured Velocity ◽

Surface Mass ◽

Ice Velocity

Abstract The continuity relationship that is often used in the study of ice sheets and ice shelves is developed by integrating the equation of continuity through the ice thickness. This equation is then integrated again with respect to horizontal distance from an ice divide, showing that the difference between the true ice velocity and the balance velocity, which is defined, is a measure of the time chance of the mass of a column through the ice thickness. The relationship is applied using data from along the “Byrd” station strain network, Antarctica. This region is found to be thinning slowly (0.03 m a−1 of ice of mean density) and uniformly, but it is still close to steady-state. The calculations would show a larger thinning rate if bottom sliding contributed more to the ice movement and integral shear contributed less, but the “Byrd” station bore-hole tilting results of Garfield and Ueda (1975, 1976), together with surface velocity measurements at “Byrd” station, indicate that most of the ice flow is by deformation within the ice mass. This large amount of internal deformation is more than that predicted by most “flow laws”, probably because of the strongly oriented ice-crystal fabric in the ice sheet. The cause of ice thinning is probably decreased surface mass balance beginning before A.D. 1550. The consistent relationship between measured velocity and balance velocity indicates that the ice flow is simple and that flow lines are in the same direction at depth as at the surface when considered smoothed over a distance of 10 km. Because the ice sheet is at present thinning, the balance velocity, calculated only from flow line and surface mass-balance data, and the somewhat mistaken assumption of steady-state is 15% less than the true ice velocity. This rather small difference confirms the use of balance-velocity estimates where velocity measurements are not available.

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Decadal-scale sensitivity of Northeast Greenland ice flow to errors in surface mass balance using ISSM

Journal of Geophysical Research Earth Surface ◽

10.1002/jgrf.20062 ◽

2013 ◽

Vol 118 (2) ◽

pp. 667-680 ◽

Cited By ~ 17

Author(s):

N-J. Schlegel ◽

E. Larour ◽

H. Seroussi ◽

M. Morlighem ◽

J. E. Box

Keyword(s):

Mass Balance ◽

Surface Mass Balance ◽

Ice Flow ◽

Surface Mass ◽

Decadal Scale ◽

Scale Sensitivity

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Surface velocity and mass balance of Livingston Island ice cap, Antarctica

The Cryosphere ◽

10.5194/tc-8-1807-2014 ◽

2014 ◽

Vol 8 (5) ◽

pp. 1807-1823 ◽

Cited By ~ 28

Author(s):

B. Osmanoglu ◽

F. J. Navarro ◽

R. Hock ◽

M. Braun ◽

M. I. Corcuera

Keyword(s):

Mass Balance ◽

Surface Velocity ◽

South Shetland Islands ◽

Surface Mass Balance ◽

Surface Mass ◽

Ice Caps ◽

Ice Cap ◽

Livingston Island ◽

Flux Gate ◽

Frontal Ablation

Abstract. The mass budget of the ice caps surrounding the Antarctica Peninsula and, in particular, the partitioning of its main components are poorly known. Here we approximate frontal ablation (i.e. the sum of mass losses by calving and submarine melt) and surface mass balance of the ice cap of Livingston Island, the second largest island in the South Shetland Islands archipelago, and analyse variations in surface velocity for the period 2007–2011. Velocities are obtained from feature tracking using 25 PALSAR-1 images, and used in conjunction with estimates of glacier ice thicknesses inferred from principles of glacier dynamics and ground-penetrating radar observations to estimate frontal ablation rates by a flux-gate approach. Glacier-wide surface mass-balance rates are approximated from in situ observations on two glaciers of the ice cap. Within the limitations of the large uncertainties mostly due to unknown ice thicknesses at the flux gates, we find that frontal ablation (−509 ± 263 Mt yr−1, equivalent to −0.73 ± 0.38 m w.e. yr−1 over the ice cap area of 697 km2) and surface ablation (−0.73 ± 0.10 m w.e. yr−1) contribute similar shares to total ablation (−1.46 ± 0.39 m w.e. yr−1). Total mass change (δM = −0.67 &plusmn 0.40 m w.e. yr−1) is negative despite a slightly positive surface mass balance (0.06 ± 0.14 m w.e. yr−1). We find large interannual and, for some basins, pronounced seasonal variations in surface velocities at the flux gates, with higher velocities in summer than in winter. Associated variations in frontal ablation (of ~237 Mt yr−1; −0.34 m w.e. yr−1) highlight the importance of taking into account the seasonality in ice velocities when computing frontal ablation with a flux-gate approach.

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