scholarly journals Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap

2017 ◽  
Vol 8 (2) ◽  
pp. 283-294
Author(s):  
Yuri V. Konovalov ◽  
Oleg V. Nagornov
Keyword(s):  
Mass Balance ◽  
Flow Line ◽  
Surface Mass Balance ◽  
Ice Streams ◽  
Surface Mass ◽  
Ice Cap ◽  
Ice Surface ◽  
Ice Surface Temperature ◽  
Severnaya Zemlya ◽  
Academy Of Sciences

Abstract. Prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap on Komsomolets Island, Severnaya Zemlya archipelago, were undertaken in this study. The experiments were based on inversions of basal friction coefficients using a two-dimensional flow-line thermocoupled model and Tikhonov's regularization method. The modeled ice temperature distributions in the cross sections were obtained using ice surface temperature histories that were inverted previously from borehole temperature profiles derived at the summit of the Academy of Sciences Ice Cap and the elevational gradient of ice surface temperature changes (about 6.5 °C km−1). Input data included interferometric synthetic aperture radar (InSAR) ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements, while the surface mass balance was adopted from previous investigations for the implementation of both the forward and inverse problems. The prognostic experiments revealed that both ice mass and ice stream extent declined for the reference time-independent surface mass balance. Specifically, the grounding line retreated: (a) along the B–B′ flow line from  ∼  40 to  ∼  30 km (the distance from the summit), (b) along the C–C′ flow line from  ∼  43 to  ∼  37 km, and (c) along the D–D′ flow line from  ∼  41 to  ∼  32 km, when considering a time period of 500 years and assuming a time-independent surface mass balance. Ice flow velocities in the ice streams decreased with time and this trend resulted in the overall decline of the outgoing ice flux. Generally, the modeled glacial evolution was in agreement with observations of deglaciation of the Severnaya Zemlya archipelago.

scholarly journals Two-dimensional prognostic experiments for fast-flowing ice streams from the Academy of Sciences Ice Cap: future modeled histories obtained for the reference surface mass balance

2015 ◽  
Vol 6 (2) ◽  
pp. 2211-2242 ◽  
Author(s):  
Y. V. Konovalov ◽  
O. V. Nagornov
Keyword(s):  
Mass Balance ◽  
Flow Line ◽  
The Arctic ◽  
Surface Mass Balance ◽  
Two Dimensional ◽  
Ice Streams ◽  
Surface Mass ◽  
Ice Cap ◽  
Ice Surface ◽  
Academy Of Sciences

Abstract. The prognostic experiments for fast-flowing ice streams on the southern side of the Academy of Sciences Ice Cap in the Komsomolets Island, Severnaya Zemlya archipelago, are implemented in this study. These experiments are based on inversions of basal friction coefficients using a two-dimensional flow-line thermo-coupled model and the Tikhonov's regularization method. The modeled ice temperature distributions in the cross-sections were obtained using the ice surface temperature histories that were inverted previously from the borehole temperature profiles derived at the Academy of Sciences Ice Cap. Input data included InSAR ice surface velocities, ice surface elevations, and ice thicknesses obtained from airborne measurements and the surface mass balance, were adopted from the prior investigations for the implementation of both the forward and inverse problems. The prognostic experiments reveal that both ice mass and ice stream extents decline for the reference time-independent surface mass balance. Specifically, the grounding line retreats (a) along the B–B' flow line from ~ 40 to ~ 30 km (the distance from the summit), (b) along the C–C' flow line from ~ 43 to ~ 37 km, and (c) along the D–D' flow line from ~ 41 to ~ 32 km considering a time period of 500 years and assuming time-independent surface mass balance. Ice flow velocities in the ice streams decrease with time and this trend results in the overall decline of the outgoing ice flux. Generally, the modeled histories are in agreement with observations of sea ice extent and thickness indicating a continual ice decline in the Arctic.

scholarly journals Local surface mass-balance reconstruction from a tephra layer – a case study on the northern slope of Mýrdalsjökull, Iceland

2016 ◽  
Vol 63 (237) ◽  
pp. 79-87 ◽  
Author(s):  
CHRISTOPH MAYER ◽  
JULIA JAENICKE ◽  
ASTRID LAMBRECHT ◽  
LUDWIG BRAUN ◽  
CHRISTOF VÖLKSEN ◽  
...  
Keyword(s):  
Mass Balance ◽  
Volcanic Eruptions ◽  
Surface Mass Balance ◽  
Ablation Zone ◽  
Tephra Layer ◽  
Surface Geometry ◽  
High Accumulation ◽  
Surface Mass ◽  
Ice Caps ◽  
Ice Cap

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.

scholarly journals COSIPY v1.2 – An open-source coupled snowpack and ice surface energy and mass balance model

2020 ◽  
Author(s):  
Tobias Sauter ◽  
Anselm Arndt ◽  
Christoph Schneider
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Mass Balance ◽  
Surface Energy Balance ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Mass Balance Model ◽  
Physical Processes ◽  
Surface Mass ◽  
Ice Surface

Abstract. Glacial changes play a key role both from a socio-economical and political, and scientific point of view. The identification and the understanding of the nature of these changes still poses fundamental challenges for climate, glacier and water research. Many studies aim to identify the climatic drivers behind the observed glacial changes using distributed surface mass and energy balance models. Distributed surface mass balance models, which translate the meteorological conditions on glaciers into local melting rates, thus offer the possibility to attribute and detect glacier mass and volume responses to changes in the climatic forcings. A well calibrated model is a suitable test-bed for sensitivity, detection and attribution analyses for many scientific applications and often serves as a tool for quantifying the inherent uncertainties. Here we present the open-source coupled snowpack and ice surface energy and mass balance model in Python COSIPY, which provides a lean, flexible and user-friendly framework for modelling distributed snow and glacier mass changes. The model has a modular structure so that the exchange of routines or parameterizations of physical processes is possible with little effort for the user. The model has a modular structure so that the exchange of routines or parameterizations of physical processes is possible with little effort for the user. The framework consists of a computational kernel, which forms the runtime environment and takes care of the initialization, the input-output routines, the parallelization as well as the grid and data structures. This structure offers maximum flexibility without having to worry about the internal numerical flow. The adaptive sub-surface scheme allows an efficient and fast calculation of the otherwise computationally demanding fundamental equations. The surface energy-balance scheme uses established standard parameterizations for radiation as well as for the energy exchange between atmosphere and surface. The schemes are coupled by solving both surface energy balance and subsurface fluxes iteratively in such that consistent surface skin temperature is returned at the interface. COSIPY uses a one-dimensional approach limited to the vertical fluxes of energy and matter but neglects any lateral processes. Accordingly, the model can be easily set up in parallel computational environments for calculating both energy balance and climatic surface mass balance of glacier surfaces based on flexible horizontal grids and with varying temporal resolution. The model is made available on a freely accessible site and can be used for non-profit purposes. Scientists are encouraged to actively participate in the extension and improvement of the model code.

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

2003 ◽  
Vol 37 ◽  
pp. 189-193 ◽  
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.

scholarly journals The Gregoriev Ice Cap length changes derived by 2-D ice flow line model for harmonic climate histories

2009 ◽  
Vol 1 (1) ◽  
pp. 55-91
Author(s):  
Y. V. Konovalov ◽  
O. V. Nagornov
Keyword(s):  
Numerical Solution ◽  
Air Temperature ◽  
Equilibrium Equation ◽  
Flow Line ◽  
Mechanical Equilibrium ◽  
Surface Mass ◽  
Ice Cap ◽  
Ice Surface ◽  
Glacier Length ◽  
Length Changes

Abstract. Different ice thickness distributions along the flow line and the flow line length changes of the Gregoriev Ice Cap, Terskey Ala-Tau, Central Asia, were obtained for some surface mass balance histories which can be considered as possible surface mass balances in the future. The ice cap modeling was performed by solving of steady state hydrodynamic equations in the case of low Reynolds number in the form of the mechanical equilibrium equation in terms of stress deviator components coupled with the continuity equation for incompressible fluid. The numerical solution was obtained by the finite difference method. A compound approximation of the ice surface boundary condition based on the extending of the mechanical equilibrium equation to ice surface points was applied. The approximation is considered as a way to overcome the problem of diagnostic equations numerical solution stability in the full model. The basal sliding can arise in the glacier tongue at certain climatic conditions and was introduced both through linear and through non-linear friction laws. A possible glacier length history, that corresponds to the regional climate changes derived from the tree-rings data, was obtained by the model. The correlations between the glacier length changes and annual air temperature histories were investigated within the simplified equation introduced by J. Oerlemans in the form of linear dependence of annual air temperature versus glacier length and time derivative of the length. The parameters of the dependence were derived from modeled glacier length histories that correspond to harmonic climate histories. The parameters variations were investigated for different periodicities of harmonic climate histories and appropriate dependences are presented in the paper. The results of the modeling are in a good agreement with the J. Oerlemans climatic model.

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

2014 ◽  
Vol 8 (5) ◽  
pp. 1807-1823 ◽  
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.

scholarly journals Regional modeling of surface mass balance on the Cook Ice Cap, Kerguelen Islands ($$49^{\circ }\mathrm{S}$$, $$69^{\circ }\mathrm{E}$$)

2019 ◽  
Vol 53 (9-10) ◽  
pp. 5909-5925 ◽  
Author(s):  
Deborah Verfaillie ◽  
Vincent Favier ◽  
Hubert Gallée ◽  
Xavier Fettweis ◽  
Cécile Agosta ◽  
...  
Keyword(s):  
Mass Balance ◽  
Regional Modeling ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Kerguelen Islands ◽  
Ice Cap

scholarly journals Surface mass balance and energy balance of the 79N Glacier (Nioghalvfjerdsfjorden, NE Greenland) modeled by linking COSIPY and Polar WRF

2021 ◽  
pp. 1-15
Author(s):  
M. T. Blau ◽  
J. V. Turton ◽  
T. Sauter ◽  
T. Mölg
Keyword(s):  
Mass Balance ◽  
Regional Climate ◽  
Atmospheric Model ◽  
High Mass ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Outlet Glacier ◽  
Surface Mass ◽  
Ice Surface ◽  
High Mass Loss

Abstract To get a better overview of atmosphere-driven mass changes at the 79N Glacier (Nioghalvfjerdsfjorden Glacier), the largest outlet glacier of the northeast Greenland ice stream, the surface mass balance (SMB) is modeled by linking the COupled Snowpack and Ice surface energy and mass-balance model in PYthon (COSIPY) with the output of a regional atmospheric model (Polar WRF) for the years 2014–2018. After a manual model optimization, the model produces reliable results when compared to observations in the region and to values from the literature. High spatial resolution (1 km) simulations reveal strong interannual variability of the SMB. Stronger surface melting increased the ablation and runoff in years with high mass loss (2016 and 2017) whereas in other years (2015 and 2018) melting and refreezing inside the snowpack dominated the mass balance (MB). A cooler regional climate with higher snowfall-driven accumulation, higher albedo and reduced surface melt in the ablation period of 2018 resulted in a positive SMB in 2018, however, the annual total MB remained negative. The results suggest a promising new dataset for gaining more insights into mass-balance processes and their contribution to the acceleration of glacier retreat in northeast Greenland.

scholarly journals A new sub-grid surface mass balance and flux model for continental-scale ice sheet modelling: testing and last glacial cycle

2015 ◽  
Vol 8 (10) ◽  
pp. 3199-3213 ◽  
Author(s):  
K. Le Morzadec ◽  
L. Tarasov ◽  
M. Morlighem ◽  
H. Seroussi
Keyword(s):  
Mass Balance ◽  
Flow Line ◽  
Ice Sheet ◽  
Coarse Grid ◽  
Surface Mass Balance ◽  
Glacial Cycle ◽  
Surface Mass ◽  
Continental Scale ◽  
The North ◽  
The Impact

Abstract. To investigate ice sheet evolution over the timescale of a glacial cycle, 3-D ice sheet models (ISMs) are typically run at "coarse" grid resolutions (10–50 km) that do not resolve individual mountains. This will introduce to-date unquantified errors in sub-grid (SG) transport, accumulation and ablation for regions of rough topography. In the past, synthetic hypsometric curves, a statistical summary of the topography, have been used in ISMs to describe the variability of these processes. However, there has yet to be detailed uncertainty analysis of this approach. We develop a new flow line SG model for embedding in coarse resolution models. A 1 km resolution digital elevation model was used to compute the local hypsometric curve for each coarse grid (CG) cell and to determine local parameters to represent the hypsometric bins' slopes and widths. The 1-D mass transport for the SG model is computed with the shallow ice approximation. We test this model against simulations from the 3-D Ice Sheet System Model (ISSM) run at 1 km grid resolution. Results show that none of the alternative parameterizations explored were able to adequately capture SG surface mass balance and flux processes. Via glacial cycle ensemble results for North America, we quantify the impact of SG model coupling in an ISM. We show that SG process representation and associated parametric uncertainties, related to the exchange of ice between the SG and CG cells, can have significant (up to 35 m eustatic sea level equivalent for the North American ice complex) impact on modelled ice sheet evolution.

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